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GuanFACINE

Pronunciation

Pronunciation

(GWAHN fa seen)

Index Terms

  • Guanfacine Hydrochloride

Dosage Forms

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

Tablet, Oral:

Tenex: 1 mg [contains fd&c red #40 aluminum lake]

Tenex: 2 mg [contains fd&c yellow #10 aluminum lake]

Generic: 1 mg, 2 mg

Tablet Extended Release 24 Hour, Oral:

Intuniv: 1 mg, 2 mg, 3 mg, 4 mg

Generic: 1 mg, 2 mg, 3 mg, 4 mg

Brand Names: U.S.

  • Intuniv
  • Tenex

Pharmacologic Category

  • Alpha2-Adrenergic Agonist
  • Antihypertensive

Pharmacology

Guanfacine is a selective alpha2A-adrenoreceptor agonist which reduces sympathetic nerve impulses, resulting in reduced sympathetic outflow and a subsequent decrease in vasomotor tone and heart rate. In addition, guanfacine preferentially binds postsynaptic alpha2A-adrenoreceptors in the prefrontal cortex and has been theorized to improve delay-related firing of prefrontal cortex neurons. As a result, underlying working memory and behavioral inhibition are affected; thereby improving symptoms associated with ADHD. Guanfacine is not a CNS stimulant.

Distribution

Vd: Immediate release: 6.3 L/kg; Extended release: Vd (apparent): Children ≥6 years: 23.7 L/kg; Adolescent: 19.9 L/kg (Boellner 2007)

Metabolism

Hepatic via CYP3A4. Approximately 50% of clearance is hepatic.

Excretion

Urine (~50% [40% to 75% of dose] as unchanged drug)

Time to Peak

Serum:

Immediate release: 2.6 hours (range: 1 to 4 hours)

Extended release: Children ≥6 years and Adolescents: 5 hours (Boellner 2007); Adults: 4 to 8 hours

Duration of Action

Antihypertensive effect: 24 hours following single dose

Half-Life Elimination

Immediate release: ~17 hours (range: 10 to 30 hours)

Extended release: Children ≥6 years: 14.4 hours; Adolescents: 18 hours (Boellner 2007); Adults: 16 hours

Protein Binding

~70%

Special Populations: Renal Function Impairment

In patients with renal impairment, clearance is reduced; plasma levels are only slightly increased. In patients on hemodialysis, dialysis clearance was ~15% of total clearance.

Special Populations: Children

Exposure to guanfacine was higher in children (6 to 12 years of age) compared with adolescents (13 to 17 years of age).

Use: Labeled Indications

Attention-deficit/hyperactivity disorder (extended release only): Treatment of attention-deficit/hyperactivity disorder (ADHD) as monotherapy and as adjunctive therapy to stimulant medications.

Hypertension (immediate release only): Management of hypertension.

Use: Unlabeled

Tic disorder; Tourette's syndrome

Contraindications

Hypersensitivity to guanfacine or any component of the formulation

Dosing: Adult

Hypertension: Immediate release: Oral: 1 mg once daily at bedtime, may increase if needed after 3 to 4 weeks of therapy to 2 mg daily at bedtime. Note: Adverse reactions increase significantly with doses above 3 mg/day.

Dosing: Geriatric

Immediate release: Refer to adult dosing. In the management of hypertension, consider lower initial doses and titrate to response (Aronow 2011).

Dosing: Pediatric

ADHD: Extended release: Children ≥6 years and Adolescents ≤17 years: Oral: Initial: 1 mg once daily; may adjust by increments of no more than 1 mg/week. Recommended target dose is 0.05 to 0.12 mg/kg/dose (1 to 7 mg) once daily, depending on clinical response and tolerability.

Maximum daily doses: Doses above the following have not been evaluated.

Monotherapy: Children 6 to 12 years: 4 mg/day; Adolescents: 13 to 17 years: 7 mg/day

Adjunct therapy (with psychostimulants): 4 mg/day

Suggested fixed target dose range for patients weighing ≥25 kg: All doses administered once daily at the same time (either in the morning or evening) not to exceed age-based maximum daily doses.

25 to 33.9 kg: 2 to 3 mg/day

34 to 41.4 kg: 2 to 4 mg/day

41.5 to 49.4 kg: 3 to 5 mg/day

49.5 to 58.4 kg: 3 to 6 mg/day

58.5 to 91 kg: 4 to 7 mg/day

>91 kg: 5 to 7 mg/day

Dosage adjustment for concomitant CYP3A4 inhibitors/inducers:

Strong CYP3A4 inhibitors: If initiating guanfacine while taking a strong CYP3A4 inhibitor or if continuing guanfacine and adding a strong CYP3A4 inhibitor, decrease guanfacine dose by 50%. If continuing guanfacine and discontinuing the strong CYP3A4 inhibitor, increase guanfacine to the recommended dose.

Strong CYP3A4 inducers: If initiating guanfacine while taking a strong CYP3A4 inducer, consider increasing guanfacine to double the recommended dose. If continuing guanfacine and adding a strong CYP3A4 inducer, consider increasing guanfacine gradually over 1 to 2 weeks to double the recommended dose. If continuing guanfacine and discontinuing the strong CYP3A4 inducer, gradually decrease guanfacine dose to the recommended dose over 1 to 2 weeks.

Conversion from immediate release to extended release: Discontinue the immediate release formulation, and titrate according to extended release recommendations.

Missed doses of extended release: If ≥2 consecutive doses are missed, consider repeating dosage titration based on patient tolerability.

Discontinuation of extended release: Gradually discontinue by tapering dose in decrements of ≤1 mg every 3 to 7 days to avoid rebound hypertension.

Hypertension: Children ≥12 years and Adolescents: Immediate release: Oral: Refer to adult dosing.

Tourette syndrome (off-label use): Children ≥6 years and Adolescents ≤16 years: Immediate release: Oral: Initial: 0.5 mg once daily at bedtime for 3 days, then 0.5 mg twice daily for 4 days, then 0.5 mg 3 times daily; may further increase dose after 7 days based on clinical response to maximum daily dose of 4 mg/day in 3 divided doses (Scahill 2001); twice daily dosing may be effective for some patients (Chappell, 1995; Cummings 2002). Note: Limited data available; greater efficacy shown in patients with ADHD comorbidity (AACAP [Murphy 2013]; ESSTS [Roessner 2011]; Pringsheim 2012; Weisman 2013).

Dosing: Renal Impairment

Immediate release: Children ≥12 years, Adolescents, and Adults: There are no specific dosage adjustments provided in the manufacturer’s labeling; however, the lower end of the dosing range is recommended in patients with renal impairment.

Extended release: Children ≥6 years and Adolescents ≤17 years: There are no dosage adjustments provided in the manufacturer’s labeling (has not been studied); however, dosage adjustments may be necessary in patients with significant renal impairment.

Hemodialysis: Immediate release or extended release: Dialysis clearance is low (~15% of total clearance).

Dosing: Hepatic Impairment

Immediate release: Children ≥12 years, Adolescents, and Adults: There are no dosage adjustments provided in the manufacturer’s labeling; however, use with caution in chronic hepatic impairment.

Extended release: Children ≥6 years and Adolescents ≤17 years: There are no dosage adjustments provided in the manufacturer’s labeling (has not been studied); however, dosage adjustments may be necessary in patients with significant hepatic impairment.

Administration

Immediate-release tablets are usually given at bedtime to minimize somnolence. Extended-release tablets should be taken at the same time each day (either morning or evening), and should not be crushed, broken, or chewed. Formulations (immediate release versus extended release) are not interchangeable.

Dietary Considerations

Extended release tablets: Do not administer with a high-fat meal due to increased exposure.

Storage

Immediate release: Store at 20°C to 25°C (68°F to 77°F).

Extended release: Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F and 86°F).

Drug Interactions

Alcohol (Ethyl): May enhance the CNS depressant effect of GuanFACINE. Avoid combination

Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification

Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy

Aprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Azelastine (Nasal): CNS Depressants may enhance the CNS depressant effect of Azelastine (Nasal). Avoid combination

Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Beta-Blockers: Alpha2-Agonists may enhance the AV-blocking effect of Beta-Blockers. Sinus node dysfunction may also be enhanced. Beta-Blockers may enhance the rebound hypertensive effect of Alpha2-Agonists. This effect can occur when the Alpha2-Agonist is abruptly withdrawn. Management: Closely monitor heart rate during treatment with a beta blocker and clonidine. Withdraw beta blockers several days before clonidine withdrawal when possible, and monitor blood pressure closely. Recommendations for other alpha2-agonists are unavailable. Exceptions: Levobunolol; Metipranolol. Consider therapy modification

Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Consider therapy modification

Bosentan: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Bradycardia-Causing Agents: May enhance the bradycardic effect of other Bradycardia-Causing Agents. Monitor therapy

Bretylium: May enhance the bradycardic effect of Bradycardia-Causing Agents. Bretylium may also enhance atrioventricular (AV) blockade in patients receiving AV blocking agents. Monitor therapy

Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine patches (Butrans brand) at 5 mcg/hr in adults when used with other CNS depressants. Consider therapy modification

Cannabis: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Ceritinib: Bradycardia-Causing Agents may enhance the bradycardic effect of Ceritinib. Management: If this combination cannot be avoided, monitor patients for evidence of symptomatic bradycardia, and closely monitor blood pressure and heart rate during therapy. Avoid combination

CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Exceptions: Levocabastine (Nasal). Monitor therapy

Conivaptan: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

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

CYP3A4 Inducers (Strong): May decrease the serum concentration of GuanFACINE. Management: Consider increasing the guanfacine dose by 2-fold when adding a strong CYP3A4 inducer. Consider therapy modification

CYP3A4 Inhibitors (Moderate): May increase the serum concentration of GuanFACINE. Management: Canadian labeling recommends an initial 50% reduction in guanfacine dose with further dose titration as needed. However, US labeling does not call for any specific guanfacine dose reduction with this combination. Monitor therapy

CYP3A4 Inhibitors (Strong): May increase the serum concentration of GuanFACINE. Management: Reduce the guanfacine dose by 50% when starting this combination. Consider therapy modification

Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates. 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

Dasatinib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Monitor therapy

Dronabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Consider therapy modification

DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy

Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates. 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

Fosaprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Fusidic Acid (Systemic): May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Hydrocodone: CNS Depressants may enhance the CNS depressant effect of Hydrocodone. Management: Consider starting with a 20% to 30% lower hydrocodone dose when using together with any other CNS depressant. Dose reductions in the other CNS depressant may also be warranted. Consider therapy modification

HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy

Idelalisib: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Iobenguane I 123: Alpha2-Agonists may diminish the therapeutic effect of Iobenguane I 123. Avoid combination

Ivabradine: Bradycardia-Causing Agents may enhance the bradycardic effect of Ivabradine. Monitor therapy

Ivacaftor: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Kava Kava: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

Lacosamide: Bradycardia-Causing Agents may enhance the AV-blocking effect of Lacosamide. Monitor therapy

Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy

Luliconazole: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Consider therapy modification

Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Metyrosine: CNS Depressants may enhance the sedative effect of Metyrosine. Monitor therapy

Mifepristone: May increase the serum concentration of CYP3A4 Substrates. Management: Minimize doses of CYP3A4 substrates, and monitor for increased concentrations/toxicity, during and 2 weeks following treatment with mifepristone. Avoid cyclosporine, dihydroergotamine, ergotamine, fentanyl, pimozide, quinidine, sirolimus, and tacrolimus. Consider therapy modification

Minocycline: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Mirtazapine: May diminish the antihypertensive effect of Alpha2-Agonists. Management: Consider avoiding concurrent use. If the combination cannot be avoided, monitor for decreased effects of alpha2-agonists if mirtazapine is initiated/dose increased, or increased effects if mirtazapine is discontinued/dose decreased. Consider therapy modification

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

Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nabilone: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Netupitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification

Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Avoid combination

Osimertinib: May increase the serum concentration of CYP3A4 Substrates. Osimertinib may decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: When oxycodone is combined with another CNS depressant, a dose reduction of one or both agents should be considered. The extended release oxycodone starting dose should be reduced 50% to 67% when initiated in patients already receiving CNS depressants. Consider therapy modification

Palbociclib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Avoid combination

Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Perampanel: May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination. Consider therapy modification

Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Monitor therapy

Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Monitor therapy

Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Monitor therapy

Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Monitor therapy

Ruxolitinib: May enhance the bradycardic effect of Bradycardia-Causing Agents. Management: Ruxolitinib Canadian product labeling recommends avoiding use with bradycardia-causing agents to the extent possible. Monitor therapy

Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Monitor therapy

Serotonin/Norepinephrine Reuptake Inhibitors: May diminish the antihypertensive effect of Alpha2-Agonists. Monitor therapy

Siltuximab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Simeprevir: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Sodium Oxybate: May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to combined use. When combined use is needed, consider minimizing doses of one or more drugs. Use of sodium oxybate with alcohol or sedative hypnotics is contraindicated. Consider therapy modification

St John's Wort: May decrease the serum concentration of GuanFACINE. Management: Consider increasing the guanfacine dose by 2-fold when adding St Johns Wort. Titrate the guanfacine dose up to a max of 8 mg/day when starting guanfacine in a patient who is taking St Johns Wort. Consider therapy modification

Stiripentol: May increase the serum concentration of CYP3A4 Substrates. Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Any CYP3A4 substrate used with stiripentol requires closer monitoring. Consider therapy modification

Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Consider therapy modification

Tapentadol: May enhance the CNS depressant effect of CNS Depressants. Management: Start tapentadol at a dose of one-third to one-half of the normal dose if being initiated in a patient who is taking another drug with CNS depressant effects. Monitor closely for evidence of excessive CNS depression. Consider therapy modification

Tetrahydrocannabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Avoid combination

Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Tofacitinib: May enhance the bradycardic effect of Bradycardia-Causing Agents. Monitor therapy

Tricyclic Antidepressants: May diminish the antihypertensive effect of Alpha2-Agonists. Consider therapy modification

Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Valproate Products: GuanFACINE may increase the serum concentration of Valproate Products. Monitor therapy

Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Consider therapy modification

Adverse Reactions

Frequency not always defined.

Cardiovascular: Hypotension (≤1% to 9%; dose-related; includes orthostatic), bradycardia (2% to 5%), atrioventricular block (≥2%), sinus arrhythmia (≥2%), syncope (1% to ≥2%), chest pain, hypertension

Central nervous system: Drowsiness (10% to 57%; dose-related), headache (4% to 28%), fatigue (5% to 22%), dizziness (4% to 16%; dose-related), insomnia (2% to 13%), irritability (5% to 8%), lethargy (3% to 8%), anxiety (2% to 5%), nightmares (3% to 4%), emotional lability (children and adolescents 6-17 years: 2% to 3%), agitation (≥2%), depression (≥2%), convulsions

Dermatologic: Skin rash (2% to 3%), pruritus (2%), pallor

Endocrine & metabolic: Weight gain (≤2% to 3%)

Gastrointestinal: Xerostomia (3% to 54%; dose-related), abdominal pain (≤8% to 19%; dose-related), decreased appetite (5% to 15%), constipation (2% to 15%; dose-related), nausea (≤5% to 7%), vomiting (2% to 7%), diarrhea (2% to 6%), dyspepsia (≥2%), stomach pain (≥2%)

Genitourinary: Impotence (≤3% to 7%), urinary incontinence (2% to 5%), urinary frequency

Hepatic: Increased serum ALT

Hypersensitivity: Hypersensitivity reaction

Neuromuscular & skeletal: Weakness (≤2% to 7%)

Respiratory: Asthma (≥2%)

Miscellaneous: Fever (8%; Biederman 2008)

<1% (Limited to important or life-threatening): Alopecia, amnesia, cardiac failure, cardiac fibrillation, cerebrovascular accident, dermatitis, dysphagia, exacerbation of cardiac disease (sinus node dysfunction, atrioventricular block), exfoliative dermatitis, hallucination, hypersensitivity reaction, hypokinesia, iritis, mania (immediate release; children), myocardial infarction, nocturia, palpitations, paresis, Raynaud phenomenon, rebound hypertension, renal failure, tachycardia, visual disturbance

Warnings/Precautions

Concerns related to adverse effects:

• Cardiovascular effects: May cause atrioventricular (AV) block, bradycardia, hypotension, orthostasis, sinus node dysfunction, and syncope; these effects are dose-dependent, more pronounced during the first month of therapy, or may worsen especially when used with other sympatholytic drugs. Monitor vital signs frequently in patients with cardiac conduction abnormalities or those concomitantly treated with other sympatholytic drugs.

• CNS effects: May cause sedation and drowsiness which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery, driving).

• Dermatological effects: Skin rash with exfoliation has been reported; discontinue guanfacine and monitor patients who develop a rash.

Disease-related concerns:

• Cardiovascular disease: Use with caution in patients with severe coronary insufficiency, recent MI, or a history of bradycardia, cardiovascular disease, heart block, hypotension, or syncope. Cautious use is also recommended in patients with conditions that predispose them to syncope (eg, orthostasis, dehydration).

• Cerebrovascular disease: Use with caution in patients with cerebrovascular disease.

• Hepatic impairment: Use with caution in patients with chronic hepatic impairment. Dosage adjustment may be necessary in severe impairment.

• Renal impairment: Use with caution in patients with chronic renal impairment. Dosage adjustment may be necessary in severe impairment.

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Dosage form specific issues:

• Product interchangeability: Formulations of guanfacine (immediate release versus extended release) are not interchangeable on a mg to mg basis because bioavailability, Cmax, and Tmax vary.

Other warnings/precautions:

• Discontinuation of therapy: Abrupt discontinuation can result in nervousness, anxiety, and, rarely, rebound hypertension (occurs 2 to 4 days after withdrawal). To minimize these effects, taper the dose in decrements of ≤1 mg every 3 to 7 days and monitor blood pressure and pulse following dosage reduction/discontinuation.

• ADHD treatment: Appropriate use: Recommended to be used as part of a comprehensive treatment program for attention-deficit disorders; safety and efficacy of long-term use for the treatment of ADHD (>2 years) have not been established (Sallee 2009).

Monitoring Parameters

Heart rate, blood pressure

When used for the treatment of ADHD, thoroughly evaluate for cardiovascular risk. Monitor heart rate, blood pressure (prior to initiation, following dosage adjustments, and periodically thereafter), and consider obtaining ECG prior to initiation (Vetter 2008).

Pregnancy Risk Factor

B

Pregnancy Considerations

Adverse events were not observed in animal reproduction studies except in doses that also caused maternal toxicity. Information related to guanfacine use during pregnancy is limited (Philipp, 1980). Untreated chronic maternal hypertension is associated with adverse events in the fetus, infant, and mother. If treatment for hypertension during pregnancy is needed, other agents are preferred (ACOG 2012).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience constipation, dry mouth, loss of strength and energy, irritability, nausea, vomiting, insomnia, abdominal pain, lack of appetite, or headache. Have patient report immediately to prescriber severe dizziness, passing out, bradycardia, arrhythmia, severe fatigue, or sexual dysfunction (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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