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Fosamprenavir

Medically reviewed by Drugs.com. Last updated on Sep 16, 2020.

Pronunciation

(FOS am pren a veer)

Index Terms

  • Fosamprenavir Calcium
  • GW433908G

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Suspension, Oral, as calcium:

Lexiva: 50 mg/mL (225 mL) [contains methylparaben, polysorbate 80, propylene glycol, propylparaben; grape bubblegum peppermint flavor]

Tablet, Oral, as calcium:

Lexiva: 700 mg

Generic: 700 mg

Brand Names: U.S.

  • Lexiva

Pharmacologic Category

  • Antiretroviral, Protease Inhibitor (Anti-HIV)

Pharmacology

Fosamprenavir is rapidly and almost completely converted to amprenavir by cellular phosphatases in vivo. Amprenavir binds to the site of HIV-1 protease activity and inhibits cleavage of viral Gag-Pol polyprotein precursors into individual functional proteins required for infectious HIV. This results in the formation of immature, noninfectious viral particles.

Absorption

63%

Metabolism

Fosamprenavir is rapidly and almost completely converted to amprenavir by cellular phosphatases in gut epithelium; amprenavir is hepatically metabolized via CYP isoenzymes (primarily CYP3A4); glucuronide conjugation of oxidized metabolites also occurs

Excretion

Minimal excretion of unchanged drug in urine (1%) and feces; 75% of dose excreted as metabolites via biliary tract into feces and 14% excreted as metabolites in urine

Time to Peak

1.5 to 4 hours (median: 2.5 hours)

Half-Life Elimination

~7.7 hours (amprenavir)

Protein Binding

~90% (to alpha1-acid glycoprotein); decreased in hepatic impairment

Special Populations: Hepatic Function Impairment

AUC of amprenavir was increased by ~22% in mild hepatic impairment, by ~70% in moderate hepatic impairment, and by ~80% in severe hepatic impairment. Protein binding also decreased.

Special Populations: Children

For children 2 to 18 years of age, the AUC is 31.4 to 93.4 mcg•h/mL, Cmax is 5 to 6.07 mcg/mL, and Cmin is 0.454 to 2.69 mcg/mL.

Use: Labeled Indications

HIV-1 infection, treatment: Treatment of HIV-1 infection, in combination with other antiretroviral agents. Note: Fosamprenavir is not recommended as a component of initial therapy for the treatment of HIV (HHS [adults] 2019).

Contraindications

Clinically significant hypersensitivity (eg, Stevens-Johnson syndrome) to fosamprenavir, amprenavir, or any component of the formulation; coadministration with drugs highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events (eg, alfuzosin, rifampin, ergot derivatives [eg, dihydroergotamine, ergonovine, ergotamine, methylergonovine], cisapride, St. John's wort, lovastatin, lomitapide, simvastatin, pimozide, delavirdine, sildenafil [when used for treatment of pulmonary arterial hypertension], midazolam, or triazolam); use of flecainide, lurasidone, or propafenone with concomitant ritonavir therapy.

Also refer to the ritonavir monograph, if used in combination with ritonavir, for additional contraindications.

Canadian labeling: Additional contraindications (not in US labeling): Coadministration with antihistamines, GI motility agents, amiodarone, diazepam, flurazepam, lidocaine (systemic), quetiapine.

Dosing: Adult

HIV-1 infection, treatment: Oral:

Antiretroviral therapy-naive patients:

Note: Fosamprenavir is not recommended as a component of initial therapy for the treatment of HIV (HHS [adults] 2019).

Unboosted regimen: 1.4 g twice daily (without ritonavir).

Ritonavir-boosted regimens:

Once-daily regimen: Fosamprenavir 1.4 g once daily plus ritonavir 100 to 200 mg once daily.

Twice-daily regimen: Fosamprenavir 700 twice daily plus ritonavir 100 mg twice daily.

Protease inhibitor-experienced patients: Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. Note: Once-daily administration is not recommended in protease inhibitor-experienced patients.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: Gene mutation and antiretroviral (ARV) resistance patterns should be evaluated (refer to https://www.iasusa.org/ for more information) when necessary.

HIV-1 infection, treatment: Note: Although FDA approved, fosamprenavir is no longer recommended for use in pediatric patients due to low exposure levels (HHS [pediatric] 2019). If used, it should be in combination with other ARV agents. Do not administer fosamprenavir (with or without ritonavir) to protease inhibitor-experienced pediatric patients <6 months of age. In addition, once-daily dosing of fosamprenavir (with or without ritonavir) is not recommended in any pediatric patient (HHS [pediatric] 2018]).

Protease inhibitor-naive patients:

Ritonavir unboosted regimen: Children ≥2 years and Adolescents: Note: Manufacturer labeling may not reflect current practice. Oral: 30 mg/kg/dose twice daily; maximum dose 1,400 mg/dose.

Ritonavir-boosted regimen: Infants, Children, and Adolescents: Note: Manufacturer labeling may not reflect current practice. Per the manufacturer, use only in infants born at ≥38 weeks GA and who are at least 28 days PNA; however, experts recommend to avoid use in infants <6 months due to low systemic exposure (HHS [pediatric] 2018): Oral:

<11 kg: Fosamprenavir 45 mg/kg/dose plus ritonavir 7 mg/kg/dose twice daily.

11 to <15 kg: Fosamprenavir 30 mg/kg/dose plus ritonavir 3 mg/kg/dose twice daily.

15 to <20 kg: Fosamprenavir 23 mg/kg/dose plus ritonavir 3 mg/kg/dose twice daily.

≥20 kg: Fosamprenavir 18 mg/kg/dose (maximum dose: 700 mg/dose) twice daily plus ritonavir 3 mg/kg/dose (maximum dose: 100 mg/dose) twice daily.

Protease inhibitor-experienced: Ritonavir-boosted regimen: Note: Manufacturer labeling may not reflect current practice. Infants ≥6 months, Children, and Adolescents: Oral:

<11 kg: Fosamprenavir 45 mg/kg/dose plus ritonavir 7 mg/kg/dose twice daily.

11 to <15 kg: Fosamprenavir 30 mg/kg/dose plus ritonavir 3 mg/kg/dose twice daily.

15 to <20 kg: Fosamprenavir 23 mg/kg/dose plus ritonavir 3 mg/kg/dose twice daily.

≥20 kg: Fosamprenavir 18 mg/kg/dose (maximum dose: 700 mg/dose) twice daily plus ritonavir 3 mg/kg/dose twice daily (maximum dose: 100 mg/dose) twice daily.

Note: When combined with ritonavir, fosamprenavir tablets may be administered to children who weigh ≥39 kg.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Administration

Oral suspension: Administer without food. Readminister dose of suspension if emesis occurs within 30 minutes after dosing. Shake suspension vigorously prior to use.

Tablet: Administer with food if taken with ritonavir. May be administered without regard to food if not taken with ritonavir.

Dietary Considerations

Adults should take oral suspension without food; however, pediatric patients should take oral suspension with food. Adult patients may take tablets without regard to food if not taken with ritonavir. Pediatric (HHS [pediatric] 2018) and adult patients should take tablets with food if taken with ritonavir.

Storage

Lexiva: Store tablets at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F). Store oral suspension at 5°C to 30°C (41°F to 86°F). Do not freeze.

Telzir [Canadian product]: Store tablets 2°C to 30°C; do not freeze and discard 25 days after opening.

Drug Interactions

Abacavir: Protease Inhibitors may decrease the serum concentration of Abacavir. Monitor therapy

Abemaciclib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Abemaciclib. Management: Monitor for increased abemaciclib toxicities if combined with moderate CYP3A4 inhibitors. Consider reducing the abemaciclib dose in 50 mg decrements if necessary. Monitor therapy

Acalabrutinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Acalabrutinib. Management: Reduce acalabrutinib dose to 100 mg once daily with concurrent use of a moderate CYP3A4 inhibitor. Monitor patient closely for both acalabrutinib response and evidence of adverse effects with any concurrent use. Consider therapy modification

Alfentanil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Alfentanil. Management: If use of alfentanil and moderate CYP3A4 inhibitors is necessary, consider dosage reduction of alfentanil until stable drug effects are achieved. Frequently monitor patients for respiratory depression and sedation when these agents are combined. Consider therapy modification

Alfuzosin: Fosamprenavir may increase the serum concentration of Alfuzosin. Avoid combination

Alitretinoin (Systemic): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Alitretinoin (Systemic). Monitor therapy

Amiodarone: Fosamprenavir may increase the serum concentration of Amiodarone. Monitor therapy

AmLODIPine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of AmLODIPine. Monitor therapy

Antidiabetic Agents: Hyperglycemia-Associated Agents may diminish the therapeutic effect of Antidiabetic Agents. Monitor therapy

Apixaban: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Apixaban. Monitor therapy

Aprepitant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Aprepitant. Avoid combination

ARIPiprazole: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of ARIPiprazole. Management: Monitor for increased aripiprazole pharmacologic effects. Aripiprazole dose adjustments may or may not be required based on concomitant therapy, indication, or dosage form. Consult full interaction monograph for specific recommendations. Monitor therapy

ARIPiprazole Lauroxil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of ARIPiprazole Lauroxil. Monitor therapy

Asunaprevir: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Asunaprevir. Avoid combination

AtorvaSTATin: Protease Inhibitors may increase the serum concentration of AtorvaSTATin. Management: See full monograph for recommended dose limits. Avoid atorvastatin with tipranavir/ritonavir. Consider therapy modification

Avanafil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Avanafil. Management: The maximum avanafil dose is 50 mg per 24-hour period when used together with a moderate CYP3A4 inhibitor. Patients receiving such a combination should also be monitored more closely for evidence of adverse effects (eg, hypotension, syncope, priapism). Consider therapy modification

Avapritinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Avapritinib. Management: Avoid use of moderate CYP3A4 inhibitors with avapritinib. If this combination cannot be avoided, reduce the avapritinib dose from 300 mg once daily to 100 mg once daily. Consider therapy modification

Axitinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Axitinib. Monitor therapy

Barnidipine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Barnidipine. Monitor therapy

Benzhydrocodone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Benzhydrocodone. Specifically, the concentration of hydrocodone may be increased. Monitor therapy

Blonanserin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Blonanserin. Monitor therapy

Bortezomib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Bortezomib. Monitor therapy

Bosentan: Protease Inhibitors may increase the serum concentration of Bosentan. Management: Dose adjustment of bosentan and increased monitoring for bosentan toxicities is necessary when these agents are combined. See full drug interaction monograph for details. Consider therapy modification

Bosutinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Bosutinib. Avoid combination

Brexpiprazole: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Brexpiprazole. Management: The brexpiprazole dose should be reduced to 25% of usual if used together with both a moderate CYP3A4 inhibitor and a strong or moderate CYP2D6 inhibitor, or if a moderate CYP3A4 inhibitor is used in a CYP2D6 poor metabolizer. Monitor therapy

Brigatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Brigatinib. Management: Avoid concurrent use of brigatinib with moderate CYP3A4 inhibitors when possible. If such a combination cannot be avoided, reduce the dose of brigatinib by approximately 40% (ie, from 180 mg to 120 mg, from 120 mg to 90 mg, or from 90 mg to 60 mg). Consider therapy modification

Budesonide (Oral Inhalation): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Budesonide (Oral Inhalation). Monitor therapy

Budesonide (Systemic): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Budesonide (Systemic). Management: Avoid the concomitant use of CYP3A4 inhibitors and oral budesonide. If patients receive both budesonide and CYP3A4 inhibitors, they should be closely monitored for signs and symptoms of corticosteroid excess. Consider therapy modification

Budesonide (Topical): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Budesonide (Topical). Avoid combination

Cabozantinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Cabozantinib. Monitor therapy

Calcium Channel Blockers (Nondihydropyridine): Protease Inhibitors may decrease the metabolism of Calcium Channel Blockers (Nondihydropyridine). Increased serum concentrations of the calcium channel blocker may increase risk of AV nodal blockade. Management: Avoid concurrent use when possible. If used, monitor for CCB toxicity. The manufacturer of atazanavir recommends a 50% dose reduction for diltiazem be considered. Saquinavir, tipranavir, and darunavir/cobicistat use with bepridil is contraindicated. Consider therapy modification

Cannabidiol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Cannabidiol. Monitor therapy

Cannabis: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Cannabis. More specifically, tetrahydrocannabinol and cannabidiol serum concentrations may be increased. Monitor therapy

Cilostazol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Cilostazol. Management: Consider reducing the cilostazol dose to 50 mg twice daily in adult patients who are also receiving moderate inhibitors of CYP3A4. Consider therapy modification

Cisapride: Protease Inhibitors may increase the serum concentration of Cisapride. This may result in QTc prolongation and malignant cardiac arrhythmias. Management: Drugs listed as exceptions to this monograph are discussed in further detail in separate drug interaction monographs. Avoid combination

Clorazepate: Fosamprenavir may increase the serum concentration of Clorazepate. Monitor therapy

Cobicistat: May increase the serum concentration of Fosamprenavir. However, the magnitude of this change is unclear, and dosing recommendations for this combination are not available. Avoid combination

Cobimetinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Cobimetinib. Management: Avoid this combination when possible. If concurrent short term (14 days or less) use cannot be avoided, reduce the cobimetinib dose from 60 mg to 20 mg daily. Avoid concomitant use in patients already receiving reduced cobimetinib doses. Consider therapy modification

Codeine: CYP3A4 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Codeine. Monitor therapy

Colchicine: Fosamprenavir may increase the serum concentration of Colchicine. Management: Colchicine is contraindicated in patients with impaired renal or hepatic function who are receiving ritonavir-boosted fosamprenavir. In those with normal renal and hepatic function, reduce colchicine dose as directed. Consider therapy modification

Copanlisib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Copanlisib. Monitor therapy

Crizotinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Crizotinib. Monitor therapy

Cyclophosphamide: Protease Inhibitors may enhance the adverse/toxic effect of Cyclophosphamide. Specifically, the incidences of neutropenia, infection, and mucositis may be increased. Monitor therapy

CYP3A4 Inducers (Moderate): May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

CYP3A4 Inducers (Strong): May increase the metabolism of CYP3A4 Substrates (High risk with Inducers). Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP3A4 Substrates (High risk with Inhibitors): CYP3A4 Inhibitors (Moderate) may decrease the metabolism of CYP3A4 Substrates (High risk with Inhibitors). Exceptions: Alitretinoin (Systemic); Bromperidol; Copanlisib; Praziquantel; Ripretinib; Trabectedin; Vinorelbine. Monitor therapy

Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification

Dapoxetine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Dapoxetine. Management: The dose of dapoxetine should be limited to 30 mg per day when used together with a moderate inhibitor of CYP3A4. Consider therapy modification

Darifenacin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Darifenacin. Monitor therapy

Deferasirox: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

Deflazacort: CYP3A4 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Deflazacort. Management: Administer one third of the recommended deflazacort dose when used together with a strong or moderate CYP3A4 inhibitor. Consider therapy modification

Delavirdine: Fosamprenavir may decrease the serum concentration of Delavirdine. The active metabolite amprenavir is likely responsible for this effect. Delavirdine may increase the serum concentration of Fosamprenavir. Specifically, delavirdine may increase concentrations of the active metabolite amprenavir. Avoid combination

DexAMETHasone (Systemic): May decrease the serum concentration of Fosamprenavir. Fosamprenavir may increase the serum concentration of DexAMETHasone (Systemic). Monitor therapy

DiazePAM: Fosamprenavir may increase the serum concentration of DiazePAM. Monitor therapy

Disopyramide: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Disopyramide. Monitor therapy

Dofetilide: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Dofetilide. Monitor therapy

Dolutegravir: Fosamprenavir may decrease the serum concentration of Dolutegravir. Specifically, Fosamprenavir/Ritonavir may decrease the serum concentration of Dolutegravir. The individual contributions of Fosamprenavir and Ritonavir to this effect are unknown. Management: Increase dolutegravir to 50 mg twice/day in adults. Increase weight based dose to twice daily in pediatric patients. See interaction monograph for details. Not recommended with Dovato or Juluca combo products. Seek alternatives if INSTI resistance. Consider therapy modification

Domperidone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Domperidone. Management: Drugs listed as exceptions to this monograph are discussed in further detail in separate drug interaction monographs. Avoid combination

DOXOrubicin (Conventional): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of DOXOrubicin (Conventional). Management: Seek alternatives to moderate CYP3A4 inhibitors in patients treated with doxorubicin whenever possible. One U.S. manufacturer (Pfizer Inc.) recommends that these combinations be avoided. Consider therapy modification

Dronabinol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Dronabinol. Monitor therapy

Efavirenz: May decrease serum concentrations of the active metabolite(s) of Fosamprenavir. Management: For once-daily fosamprenavir/ritonavir with efavirenz, increase ritonavir dose to 300 mg/day in adult patients. No ritonavir dose adjustment is required if using twice-daily fosamprenavir/ritonavir. Consider therapy modification

Eletriptan: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Eletriptan. Management: The use of eletriptan within 72 hours of a moderate CYP3A4 inhibitor should be avoided. Consider therapy modification

Elexacaftor, Tezacaftor, and Ivacaftor: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Elexacaftor, Tezacaftor, and Ivacaftor. Management: When combined with moderate CYP3A4 inhibitors, two elexacaftor/tezacaftor/ivacaftor (100 mg/50 mg/75 mg) tablets should be given in the morning, every other day. Ivacaftor (150 mg) should be given in the morning, every other day on alternate days. Consider therapy modification

Eliglustat: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Eliglustat. Management: Reduce eliglustat dose to 84 mg daily in CYP2D6 EMs when used with moderate CYP3A4 inhibitors. Use in CYP2D6 EMs who are also taking strong or moderate CYP2D6 inhibitors is contraindicated. Avoid use of moderate CYP3A4 inhibitors in CYP2D6 IMs or PMs. Consider therapy modification

Encorafenib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Encorafenib. Management: Avoid use of encorafenib and moderate CYP3A4 inhibitors when possible. If combined, decrease the encorafenib dose from 450 mg to 225 mg; 300 mg to 150 mg; and 225 mg or 150 mg to 75 mg. Resume prior dose once inhibitor discontinued for 3 to 5 half-lives. Consider therapy modification

Enfuvirtide: Protease Inhibitors may increase the serum concentration of Enfuvirtide. Enfuvirtide may increase the serum concentration of Protease Inhibitors. Monitor therapy

Entrectinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Entrectinib. Management: Avoid moderate CYP3A4 inhibitors during treatment with entrectinib. Reduce dose to 200 mg/day if combination cannot be avoided in adults and those 12 yrs of age or older with a BSA of at least 1.5 square meters. Avoid if BSA is less than 1.5 square meters Consider therapy modification

Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Concurrent use of enzalutamide with CYP3A4 substrates that have a narrow therapeutic index should be avoided. Use of enzalutamide and any other CYP3A4 substrate should be performed with caution and close monitoring. Consider therapy modification

Eplerenone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Eplerenone. Management: When used concomitantly with moderate inhibitors of CYP3A4, eplerenone dosing recommendations vary by indication and international labeling. See full drug interaction monograph for details. Consider therapy modification

Erdafitinib: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

Ergot Derivatives: Protease Inhibitors may increase the serum concentration of Ergot Derivatives. Exceptions: Cabergoline; Lisuride; Nicergoline; Pergolide. Avoid combination

Estrogen Derivatives: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Estrogen Derivatives. Monitor therapy

Estrogen Derivatives (Contraceptive): Protease Inhibitors may decrease the serum concentration of Estrogen Derivatives (Contraceptive). Management: Use oral contraceptives containing at least 35mcg ethinyl estradiol with atazanavir/ritonavir, or no more than 30mcg in patients receiving atazanavir alone. Use of an alternative, non-hormonal contraceptive is recommended with other protease inhibitors. Consider therapy modification

Etravirine: May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Specifically, amprenavir concentrations may increase. Avoid combination

Everolimus: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Everolimus. Monitor therapy

Fedratinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Fedratinib. Monitor therapy

FentaNYL: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of FentaNYL. Management: Consider fentanyl dose reductions when combined with a moderate CYP3A4 inhibitor. Monitor for respiratory depression and sedation. Upon discontinuation of a CYP3A4 inhibitor, consider a fentanyl dose increase; monitor for signs and symptoms of withdrawal. Consider therapy modification

Flecainide: Fosamprenavir may increase the serum concentration of Flecainide. Management: Concurrent use of ritonavir-boosted fosamprenavir with flecainide is contraindicated. The use of non-ritonavir-boosted fosamprenavir with flecainide is not specifically contraindicated but should only be undertaken with caution. Avoid combination

Flibanserin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Flibanserin. Management: Use of flibanserin with moderate CYP3A4 inhibitors is contraindicated. If starting flibanserin, start 2 weeks after the last dose of the CYP3A4 inhibitor. If starting a CYP3A4 inhibitor, start 2 days after the last dose of flibanserin. Avoid combination

Flurazepam: Fosamprenavir may increase the serum concentration of Flurazepam. Monitor therapy

Fluticasone (Oral Inhalation): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Fluticasone (Oral Inhalation). Monitor therapy

Fosaprepitant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Fosaprepitant. Avoid combination

Fosphenytoin: May decrease the serum concentration of Fosamprenavir. Fosamprenavir may decrease the serum concentration of Fosphenytoin. Specifically, fosamprenavir boosted with ritonavir may decrease phenytoin concentrations. Monitor therapy

Garlic: May decrease the serum concentration of Protease Inhibitors. Management: Concurrent use of garlic supplements with protease inhibitors is not recommended. If this combination is used, monitor closely for altered serum concentrations/effects of protease inhibitors, and particularly for signs/symptoms of therapeutic failure. Consider therapy modification

Gilteritinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Gilteritinib. Monitor therapy

GuanFACINE: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of GuanFACINE. Management: Reduce the extended-release guanfacine dose 50% when combined with a moderate CYP3A4 inhibitor. Monitor for increased guanfacine toxicities when these agents are combined. Consider therapy modification

Halofantrine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Halofantrine. Management: Extreme caution, with possibly increased monitoring of ECGs, should be used if halofantrine is combined with moderate CYP3A4 inhibitors. Drugs listed as exceptions to this monograph are discussed in separate drug interaction monographs. Monitor therapy

Histamine H2 Receptor Antagonists: May decrease the serum concentration of Fosamprenavir. Cimetidine may also inhibit the metabolism of the active metabolite amprenavir, making its effects on fosamprenavir/amprenavir concentrations difficult to predict. Monitor therapy

HYDROcodone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of HYDROcodone. Monitor therapy

Ibrutinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ibrutinib. Management: When treating B-cell malignancies, decrease ibrutinib to 280 mg daily when combined with moderate CYP3A4 inhibitors. When treating graft versus host disease, monitor patients closely and reduce the ibrutinib dose as needed based on adverse reactions. Consider therapy modification

Ifosfamide: CYP3A4 Inhibitors (Moderate) may decrease serum concentrations of the active metabolite(s) of Ifosfamide. Monitor therapy

Imatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Imatinib. Monitor therapy

Itraconazole: May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Specifically, amprenavir concentrations may be increased. Fosamprenavir may increase the serum concentration of Itraconazole. Management: Limit the adult maximum itraconazole dose to 200 mg/day with fosamprenavir/ritonavir. In patients receiving fosamprenavir without ritonavir, patients receiving greater than 400 mg/day itraconazole may also require dose reduction. Consider therapy modification

Ivabradine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ivabradine. Avoid combination

Ivacaftor: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ivacaftor. Management: Ivacaftor dose reductions may be required; consult full drug interaction monograph content for age- and weight-specific dosage recommendations. Consider therapy modification

Ivosidenib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ivosidenib. Management: Avoid use of moderate CYP3A4 inhibitors with ivosidenib whenever possible. If combined, monitor for increased ivosidenib toxicities. Drugs listed as exceptions are discussed in further detail in separate drug interaction monographs. Consider therapy modification

Ketoconazole (Systemic): May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Specifically, amprenavir concentrations may be increased. Fosamprenavir may increase the serum concentration of Ketoconazole (Systemic). Management: Limit the adult maximum ketoconazole dose to 200 mg/day with fosamprenavir/ritonavir. In patients receiving fosamprenavir without ritonavir, patients receiving greater than 400 mg/day ketoconazole may also require dose reduction. Consider therapy modification

Lapatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lapatinib. Monitor therapy

Larotrectinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Larotrectinib. Monitor therapy

Lefamulin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lefamulin. Management: Monitor for lefamulin adverse effects during coadministration of lefamulin tablets with moderate CYP3A4 inhibitors. Monitor therapy

Lemborexant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lemborexant. Avoid combination

Lercanidipine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lercanidipine. Monitor therapy

Levamlodipine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Levamlodipine. Monitor therapy

Levomethadone: Fosamprenavir may decrease the serum concentration of Levomethadone. Monitor therapy

Lomitapide: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lomitapide. Avoid combination

Lopinavir: Fosamprenavir may decrease the serum concentration of Lopinavir. Specifically, amprenavir (the active metabolite of fosamprenavir) may decrease the serum concentration of lopinavir. Lopinavir may decrease the serum concentration of Fosamprenavir. Specifically, lopinavir/ritonavir may decrease the serum concentration of amprenavir (the active metabolite of fosamprenavir) Avoid combination

Lorlatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lorlatinib. Monitor therapy

Lovastatin: Protease Inhibitors may increase the serum concentration of Lovastatin. Avoid combination

Lumateperone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lumateperone. Avoid combination

Lurasidone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lurasidone. Management: US labeling recommends reducing lurasidone dose by 50% with a moderate CYP3A4 inhibitor and initiating 20 mg/day, max 80 mg/day. Some non-US labels recommend initiating lurasidone 20 mg/day, max 40 mg/day. Avoid concurrent use of grapefruit products. Consider therapy modification

Lurbinectedin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Lurbinectedin. Management: Avoid concomitant use of lurbinectedin and moderate CYP3A4 inhibitors when possible. If combined, consider a lurbinectedin dose reduction as clinically indicated. Consider therapy modification

Macitentan: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Macitentan. Monitor therapy

Manidipine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Manidipine. Monitor therapy

Meperidine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Meperidine. Monitor therapy

Methadone: May decrease serum concentrations of the active metabolite(s) of Fosamprenavir. Specifically, amprenavir concentrations may be reduced. This effect has been demonstrated with Amprenavir alone but not with Fosamprenavir / Ritonavir. The potential impact on Fosamprenavir alone has not been investigated. Fosamprenavir may decrease the serum concentration of Methadone. Monitor therapy

Midazolam: Protease Inhibitors may increase the serum concentration of Midazolam. Management: Oral midazolam contraindicated with all protease inhibitors. IV midazolam contraindicated with fosamprenavir and nelfinavir; other protease inhibitors recommend caution, close monitoring, and consideration of lower IV midazolam doses with concurrent use. Avoid combination

MiFEPRIStone: Fosamprenavir may increase the serum concentration of MiFEPRIStone. Management: Limit mifepristone adult dose, when used for treatment of hyperglycemia in Cushing's syndrome, to a maximum of 600 mg/day when combined with fosamprenavir. Monitor for increased mifepristone toxicity regardless of dose or indication. Consider therapy modification

Mirodenafil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Mirodenafil. Monitor therapy

Mitotane: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Doses of CYP3A4 substrates may need to be adjusted substantially when used in patients being treated with mitotane. Consider therapy modification

Naldemedine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Naldemedine. Monitor therapy

Nalfurafine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Nalfurafine. Monitor therapy

Naloxegol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Naloxegol. Management: The use of naloxegol and moderate CYP3A4 inhibitors should be avoided. If concurrent use is unavoidable, reduce naloxegol dose to 12.5 mg once daily and monitor for signs of opiate withdrawal (eg, hyperhidrosis, chills, diarrhea, anxiety, irritability). Consider therapy modification

Nefazodone: Protease Inhibitors may increase the serum concentration of Nefazodone. Management: Consider alternatives to, or reduced doses of, nefazodone in patients treated with HIV protease inhibitors. Monitor patients receiving these combinations closely for toxic effects of nefazodone. Consider therapy modification

Neratinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Neratinib. Monitor therapy

Nevirapine: May decrease serum concentrations of the active metabolite(s) of Fosamprenavir. Management: Coadministration of nevirapine and fosamprenavir is not recommended without concurrent ritonavir. However, when nevirapine and fosamprenavir/ritonavir (twice daily) are used in combination, no dose adjustment is required. Consider therapy modification

NiMODipine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of NiMODipine. Monitor therapy

Olaparib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Olaparib. Management: Avoid use of moderate CYP3A4 inhibitors with olaparib, if possible. If such concurrent use cannot be avoided, the dose of olaparib tablets should be reduced to 150 mg twice daily and the dose of olaparib capsules should be reduced to 200 mg twice daily. Consider therapy modification

Oliceridine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Oliceridine. Monitor therapy

Ombitasvir, Paritaprevir, Ritonavir, and Dasabuvir: May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Fosamprenavir may increase the serum concentration of Ombitasvir, Paritaprevir, Ritonavir, and Dasabuvir. Management: Use of ritonavir-boosted fosamprenavir with ombitasvir/paritaprevir/ritonavir/dasabuvir is not recommended. Consider a reduced dose of fosamprenavir 1400 mg once daily (unboosted) when used with ombitasvir/paritaprevir/ritonavir/dasabuvir. Consider therapy modification

Orlistat: May decrease the serum concentration of Antiretroviral Agents. Monitor therapy

OxyCODONE: CYP3A4 Inhibitors (Moderate) may enhance the adverse/toxic effect of OxyCODONE. CYP3A4 Inhibitors (Moderate) may increase the serum concentration of OxyCODONE. Serum concentrations of the active metabolite Oxymorphone may also be increased. Monitor therapy

PARoxetine: Fosamprenavir may decrease the serum concentration of PARoxetine. The active metabolite amprenavir is likely responsible for this effect. Monitor therapy

PAZOPanib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of PAZOPanib. Monitor therapy

Pemigatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Pemigatinib. Management: If combined use cannot be avoided, reduce the pemigatinib dose from 13.5 mg daily to 9 mg daily, or from 9 mg daily to 4.5 mg daily. Resume prior pemigatinib dose after stopping the moderate inhibitor once 3 half-lives of the inhibitor has passed. Consider therapy modification

Pexidartinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Pexidartinib. Management: Avoid use of pexidartinib with moderate CYP3A4 inhibitors if possible. If combined, the pexidartinib dose should be reduced. Decrease 800 mg or 600 mg daily doses to 200 mg twice daily. Decrease doses of 400 mg per day to 200 mg once daily. Consider therapy modification

Phenytoin: Fosamprenavir may decrease the serum concentration of Phenytoin. Specifically, fosamprenavir boosted with ritonavir may decrease phenytoin concentrations. Phenytoin may decrease the serum concentration of Fosamprenavir. Specifically, phenytoin may decrease the concentration of the active metabolite amprenavir. Monitor therapy

Pimecrolimus: CYP3A4 Inhibitors (Moderate) may decrease the metabolism of Pimecrolimus. Monitor therapy

Pimozide: Protease Inhibitors may increase the serum concentration of Pimozide. Avoid combination

Pimozide: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Pimozide. Avoid combination

Posaconazole: May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Fosamprenavir may decrease the serum concentration of Posaconazole. Monitor therapy

Progestins (Contraceptive): May decrease serum concentrations of the active metabolite(s) of Fosamprenavir. Fosamprenavir may decrease the serum concentration of Progestins (Contraceptive). Management: Consider using an alternative or additional means of contraception. Injected depot medroxyprogesterone acetate may be used without a need for additional contraception. Consider therapy modification

Propafenone: Fosamprenavir may increase the serum concentration of Propafenone. Management: Concurrent use of ritonavir-boosted fosamprenavir with propafenone is contraindicated. The use of non-ritonavir-boosted fosamprenavir with propafenone is not specifically contraindicated but should only be undertaken with caution. Avoid combination

Protease Inhibitors: May increase the serum concentration of other Protease Inhibitors. Management: Atazanavir--indinavir combination contraindicated. Tipranavir/ritonavir or atazanavir/ritonavir not recommended with other protease inhibitors (PI). Darunavir/cobicistat not recommended with PI that require boosting.Other combos may require dose changes. Consider therapy modification

QuiNIDine: Fosamprenavir may increase the serum concentration of QuiNIDine. Monitor therapy

Raltegravir: Fosamprenavir may decrease the serum concentration of Raltegravir. Raltegravir may decrease the serum concentration of Fosamprenavir. Avoid combination

Ranolazine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ranolazine. Management: Limit the ranolazine dose to a maximum of 500 mg twice daily in patients concurrently receiving moderate CYP3A4 inhibitors. Monitor for increased ranolazine effects and toxicities during concomitant use. Consider therapy modification

Rifabutin: Fosamprenavir may increase serum concentrations of the active metabolite(s) of Rifabutin. Rifabutin may increase the serum concentration of Fosamprenavir. Fosamprenavir may increase the serum concentration of Rifabutin. Management: Reduce rifabutin doses. See full monograph for specific recommendations. Consider therapy modification

RifAMPin: May decrease the serum concentration of Fosamprenavir. Specifically, concentrations of amprenavir (active metabolite) may be decreased. Avoid combination

Rimegepant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Rimegepant. Management: Avoid a second dose of rimegepant within 48 hours when used concomitantly with moderate CYP3A4 inhibitors. Consider therapy modification

Rosuvastatin: Protease Inhibitors may increase the serum concentration of Rosuvastatin. Management: Limit rosuvastatin to 5 mg daily in patients receiving atazanavir/ritonavir or lopinavir/ritonavir. Patients receiving fosamprenavir/ritonavir or tipranavir/ritonavir do require dose adjustments if rosuvastatin is used concomitantly. Consider therapy modification

Rupatadine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Rupatadine. Monitor therapy

Ruxolitinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ruxolitinib. Monitor therapy

Salmeterol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Salmeterol. Monitor therapy

Sarilumab: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

SAXagliptin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of SAXagliptin. Monitor therapy

Selpercatinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Selpercatinib. Management: Avoid combination if possible. If use is necessary, reduce selpercatinib dose as follows: from 120 mg twice/day to 80 mg twice/day, or from 160 mg twice/day to 120 mg twice/day. Consider therapy modification

Selumetinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Selumetinib. Management: Avoid concomitant use when possible. If combined, selumetinib dose reductions are recommended and vary based on body surface area and selumetinib dose. For details, see the full drug interaction monograph or selumetinib prescribing information. Consider therapy modification

Sildenafil: Protease Inhibitors may increase the serum concentration of Sildenafil. Management: Erectile dysfunction: sildenafil max = 25 mg/48 hrs with ritonavir, atazanavir, or darunavir; starting dose = 25 mg with other protease inhibitors (adult doses). Contraindicated if sildenafil being used for pulmonary arterial hypertension. Consider therapy modification

Silodosin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Silodosin. Monitor therapy

Siltuximab: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

Simeprevir: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Simeprevir. Avoid combination

Simeprevir: Protease Inhibitors may increase the serum concentration of Simeprevir. Simeprevir may increase the serum concentration of Protease Inhibitors. Avoid combination

Simvastatin: Protease Inhibitors may increase the serum concentration of Simvastatin. Avoid combination

Sirolimus: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Sirolimus. Management: Monitor for increased serum concentrations of sirolimus if combined with a moderate CYP3A4 inhibitor. Lower initial sirolimus doses or sirolimus dose reductions will likely be required. Consider therapy modification

Sonidegib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Sonidegib. Management: Avoid concomitant use of sonidegib and moderate CYP3A4 inhibitors when possible. When concomitant use cannot be avoided, limit CYP3A4 inhibitor use to less than 14 days and monitor for sonidegib toxicity (particularly musculoskeletal adverse reactions). Consider therapy modification

St John's Wort: May increase the metabolism of Protease Inhibitors. Avoid combination

SUNItinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of SUNItinib. Monitor therapy

Suvorexant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Suvorexant. Management: The recommended dose of suvorexant is 5 mg daily in patients receiving a moderate CYP3A4 inhibitor. The dose can be increased to 10 mg daily (maximum dose) if necessary for efficacy. Consider therapy modification

Tacrolimus (Systemic): Protease Inhibitors may decrease the metabolism of Tacrolimus (Systemic). Management: Tacrolimus dose reductions may be required when starting or altering a protease inhibitor. Some patients may required less than 1 mg/week of tacrolimus during coadministration with a protease inhibitor. Monitor plasma concentrations and response. Consider therapy modification

Tacrolimus (Topical): Protease Inhibitors may decrease the metabolism of Tacrolimus (Topical). Monitor therapy

Tadalafil: Fosamprenavir may increase the serum concentration of Tadalafil. Management: Initiate tadalafil for pulmonary arterial hypertension at 20 mg after at least 1 week of fosamprenavir therapy. Increase to tadalafil 40 mg as tolerated. For erectile dysfunction, limit the tadalafil dose to 10 mg every 72 hours. Consider therapy modification

Tamsulosin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tamsulosin. Monitor therapy

Tazemetostat: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tazemetostat. Management: Avoid when possible. If combined, reduce tazemetostat dose from 800 mg twice daily to 400 mg twice daily, from 600 mg twice daily to 400 mg in AM and 200 mg in PM, or from 400 mg twice daily to 200 mg twice daily. Consider therapy modification

Telithromycin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Telithromycin. Monitor therapy

Tetrahydrocannabinol: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tetrahydrocannabinol. Monitor therapy

Tezacaftor and Ivacaftor: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tezacaftor and Ivacaftor. Management: If combined with moderate CYP3A4 inhibitors, give tezacaftor/ivacaftor in the morning, every other day; give ivacaftor in the morning, every other day on alternate days. Tezacaftor/ivacaftor dose depends on age and weight; see full Lexi-Interact monograph Consider therapy modification

Ticagrelor: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ticagrelor. Monitor therapy

Tipranavir: May decrease the serum concentration of Protease Inhibitors. Avoid combination

Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Monitor therapy

Tofacitinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tofacitinib. Monitor therapy

Tolvaptan: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Tolvaptan. Management: Avoid this combination with Samsca brand of tolvaptan. Reduce dose for Jynarque brand: 90 mg AM and 30 mg PM, reduce to 45 mg AM and 15 mg PM; 60 mg AM and 30 mg PM, reduce to 30 mg AM and 15 mg PM; 45 mg AM and 15 mg PM, reduce to 15 mg AM and PM. Consider therapy modification

Trabectedin: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Trabectedin. Monitor therapy

Triazolam: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Triazolam. Management: Consider triazolam dose reduction in patients receiving concomitant moderate CYP3A4 inhibitors. Consider therapy modification

Ubrogepant: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ubrogepant. Management: Use an initial ubrogepant dose of 50 mg and avoid a second dose for 24 hours when used with moderate CYP3A4 inhibitors. Consider therapy modification

Udenafil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Udenafil. Monitor therapy

Ulipristal: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Ulipristal. Management: This is specific for when ulipristal is being used for signs/symptoms of uterine fibroids (Canadian indication). When ulipristal is used as an emergency contraceptive, patients receiving this combination should be monitored for ulipristal toxicity. Avoid combination

Valproate Products: Protease Inhibitors may decrease the serum concentration of Valproate Products. Monitor therapy

Vardenafil: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Vardenafil. Management: Limit Levitra (vardenafil) dose to a single 5 mg dose within a 24-hour period if combined with moderate CYP3A4 inhibitors. Avoid concomitant use of Staxyn (vardenafil) and moderate CYP3A4 inhibitors. Combined use is contraindicated outside of the US. Consider therapy modification

Vemurafenib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Vemurafenib. Monitor therapy

Venetoclax: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Venetoclax. Management: Reduce the venetoclax dose by at least 50% in patients requiring concomitant treatment with moderate CYP3A4 inhibitors. Resume the previous venetoclax dose 2 to 3 days after discontinuation of moderate CYP3A4 inhibitors. Consider therapy modification

Vilazodone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Vilazodone. Monitor therapy

VinBLAStine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of VinBLAStine. Monitor therapy

VinCRIStine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of VinCRIStine. Monitor therapy

VinCRIStine (Liposomal): CYP3A4 Inhibitors (Moderate) may increase the serum concentration of VinCRIStine (Liposomal). Monitor therapy

Vindesine: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Vindesine. Monitor therapy

Voriconazole: May increase serum concentrations of the active metabolite(s) of Fosamprenavir. Specifically, amprenavir concentrations may be increased. Fosamprenavir may increase the serum concentration of Voriconazole. Monitor therapy

Warfarin: Fosamprenavir may increase the serum concentration of Warfarin. Monitor therapy

Zanubrutinib: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Zanubrutinib. Management: Decrease the zanubrutinib dose to 80 mg twice daily during coadministration with a moderate CYP3A4 inhibitor. Further dose adjustments may be required for zanubrutinib toxicities, refer to prescribing information for details. Consider therapy modification

Zidovudine: Protease Inhibitors may decrease the serum concentration of Zidovudine. Monitor therapy

Zopiclone: CYP3A4 Inhibitors (Moderate) may increase the serum concentration of Zopiclone. Management: The starting adult dose of zopiclone should not exceed 3.75 mg if combined with a moderate CYP3A4 inhibitor. Monitor patients for signs and symptoms of zopiclone toxicity if these agents are combined. Consider therapy modification

Adverse Reactions

>10%:

Dermatologic: Skin rash (≤19%; onset: ~11 days; duration: ~13 days)

Endocrine & metabolic: Hypertriglyceridemia (>750 mg/dL: ≤11%)

Gastrointestinal: Diarrhea (5% to 13%; moderate-to-severe)

1% to 10%:

Central nervous system: Fatigue (2% to 4%; moderate-to-severe), headache (2% to 4%; moderate-to-severe)

Dermatologic: Pruritus (7% to 8%)

Endocrine & metabolic: Hyperglycemia (>251 mg/dL: ≤2%)

Gastrointestinal: Increased serum lipase (>2x ULN: 5% to 8%), nausea (3% to 7%; moderate-to-severe), vomiting (2% to 6%; moderate-to-severe), abdominal pain (≤2%; moderate-to-severe)

Hematologic & oncologic: Neutropenia (<750 cells/mm3: 3%)

Hepatic: Increased serum transaminases (>5x ULN: 4% to 8%)

<1%, postmarketing, and/or case reports: Angioedema, cerebrovascular accident, hypercholesterolemia, myocardial infarction, nephrolithiasis, oral paresthesia, Stevens-Johnson syndrome

Warnings/Precautions

Concerns related to adverse effects:

• Body fat increase: May cause an increase in body fat.

• Hemolytic anemia: Acute hemolytic anemia has been reported in association with amprenavir use.

• Hepatic effects: May cause transaminase elevations, hepatitis, and/or exacerbate preexisting hepatic dysfunction; use with caution in patients with underlying hepatic disease, such as hepatitis B or C or cirrhosis.

• Hypersensitivity reactions: Protease inhibitors have been associated with a variety of hypersensitivity events (some severe), including rash, anaphylaxis (rare), angioedema, bronchospasm, erythema multiforme, and/or Stevens-Johnson syndrome (rare). It is generally recommended to discontinue treatment if severe rash or moderate symptoms accompanied by other systemic symptoms occur.

• Immune reconstitution syndrome: Patients may develop immune reconstitution syndrome resulting in the occurrence of an inflammatory response to an indolent or residual opportunistic infection during initial HIV treatment or activation of autoimmune disorders (eg, Graves disease, polymyositis, Guillain-Barré syndrome) later in therapy; further evaluation and treatment may be required.

• Lipid elevations: Increases in total cholesterol and triglycerides have been reported; screening should be done prior to therapy and periodically throughout treatment.

• Nephrolithiasis: Cases have been reported in postmarketing surveillance; temporary or permanent discontinuation of therapy should be considered if symptoms develop.

• Sulfonamide allergy: Use with caution in patients with sulfonamide allergy. In clinical trials, the incidence of rash did not differ appreciably in patients with or without a history of sulfonamide allergy.

Disease-related concerns:

• Diabetes: Changes in glucose tolerance, hyperglycemia, exacerbation of diabetes, diabetic ketoacidosis, and new-onset diabetes mellitus have been reported in patients receiving protease inhibitors.

• Hemophilia A or B: Use with caution in patients with hemophilia A or B; increased bleeding during protease inhibitor therapy has been reported.

• Hepatic impairment: Use with caution; dosage adjustment required.

Special populations:

• Protease inhibitor-experienced adults: Once-daily fosamprenavir/ritonavir is not recommended in protease inhibitor-experienced adults.

Dosage forms specific issues:

• Polysorbate 80: Some dosage forms may contain polysorbate 80 (also known as Tweens). Hypersensitivity reactions, usually a delayed reaction, have been reported following exposure to pharmaceutical products containing polysorbate 80 in certain individuals (Isaksson 2002; Lucente 2000; Shelley 1995). Thrombocytopenia, ascites, pulmonary deterioration, and renal and hepatic failure have been reported in premature neonates after receiving parenteral products containing polysorbate 80 (Alade 1986; CDC 1984).

• Propylene glycol: Some dosage forms may contain propylene glycol; large amounts are potentially toxic and have been associated with hyperosmolality, lactic acidosis, seizures, and respiratory depression; use caution (AAP 1997; Zar 2007).

Monitoring Parameters

Prior to initiation and periodically during therapy, monitor viral load, CD4 count, glucose; triglycerides and cholesterol; liver function tests (in patients with underlying hepatitis B or C)

Reproductive Considerations

Based on the Health and Humans Services (HHS) perinatal HIV guidelines, fosamprenavir (boosted or unboosted) is not one of the recommended antiretroviral agents for use in females living with HIV who are trying to conceive.

Females living with HIV not planning a pregnancy may use any available type of contraception, considering possible drug interactions and contraindications of the specific method. Consult drug interactions database for more detailed information specific to use of fosamprenavir and specific contraceptive methods (HHS [perinatal] 2019).

Pregnancy Considerations

Fosamprenavir crosses the human placenta.

Outcome information specific to fosamprenavir use in pregnancy is no longer being reviewed and updated in the Health and Human Services (HHS) perinatal guidelines. Maternal antiretroviral therapy (ART) may be associated with adverse pregnancy outcomes, including preterm delivery, stillbirth, low birth weight, and small for gestational age infants. Actual risks may be influenced by maternal factors such as disease severity, gestational age at initiation of therapy, and specific ART regimen; therefore, close fetal monitoring is recommended. Because there is clear benefit to appropriate treatment, maternal ART should not be withheld due to concerns for adverse neonatal outcomes. Long-term follow-up is recommended for all infants exposed to antiretroviral medications; children without HIV but who were exposed to ART in utero and develop significant organ system abnormalities of unknown etiology (particularly of the CNS or heart) should be evaluated for potential mitochondrial dysfunction. Hyperglycemia, new onset of diabetes mellitus, or diabetic ketoacidosis have been reported with protease inhibitors; it is not clear if pregnancy increases this risk. Consider performing the standard glucose screening test earlier in pregnancy in women who initiated protease inhibitor therapy prior to conception.

Based on the HHS perinatal HIV guidelines, fosamprenavir (boosted or unboosted), is not one of the recommended antiretroviral agents for use during pregnancy.

In general, ART is recommended for all pregnant females living with HIV to keep the viral load below the limit of detection and reduce the risk of perinatal transmission. Therapy should be individualized following a discussion of the potential risks and benefits of treatment during pregnancy. Monitoring of pregnant females is more frequent than in nonpregnant adults. ART should be continued postpartum for all females living with HIV and can be modified after delivery.

Health care providers are encouraged to enroll pregnant females exposed to antiretroviral medications as early in pregnancy as possible in the Antiretroviral Pregnancy Registry (1-800-258-4263 or http://www.APRegistry.com). Health care providers caring for pregnant females living with HIV and their infants may contact the National Perinatal HIV Hotline (1-888-448-8765) for clinical consultation (HHS [perinatal] 2019).

Patient Education

What is this drug used for?

• It is used to treat HIV infection.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Itching

• Headache

• Diarrhea

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Infection

• Liver problems like dark urine, fatigue, lack of appetite, nausea, abdominal pain, light-colored stools, vomiting, or yellow skin

• High blood sugar like confusion, fatigue, increased thirst, increased hunger, passing a lot of urine, flushing, fast breathing, or breath that smells like fruit

• Chest pain

• Severe nausea

• Severe vomiting

• Side pain

• Passing a lot of urine

• Increased thirst

• Weight loss

• Painful urination

• Back pain

• Abdominal pain

• Blood in the urine

• Numbness or tingling of mouth

• Severe dizziness

• Passing out

• Shortness of breath

• Sweating a lot

• Severe loss of strength and energy

• Change in body fat

• Stevens-Johnson syndrome/toxic epidermal necrolysis like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in mouth, throat, nose, or eyes

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine's uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.