Medically reviewed on September 10, 2018

Pronunciation

(a bir A ter one AS e tate)

Index Terms

• Abiraterone
• Abiraterone Acetate Fine Particle (Yonsa)
• Abiraterone Acetate Micronized (Yonsa)
• Abiraterone Acetate Originator (Zytiga)
• CB7630

Dosage Forms

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

Tablet, Oral:

Yonsa: 125 mg

Zytiga: 250 mg, 500 mg

Brand Names: U.S.

• Yonsa
• Zytiga

Pharmacologic Category

• Antiandrogen
• Antineoplastic Agent, Antiandrogen

Pharmacology

Abiraterone selectively and irreversibly inhibits CYP17 (17 alpha-hydroxylase/C17,20-lyase), an enzyme required for androgen biosynthesis which is expressed in testicular, adrenal, and prostatic tumor tissues. Inhibits the formation of the testosterone precursors dehydroepiandrosterone (DHEA) and androstenedione.

Distribution

V_dss: 19,669 ± 13,358 L

Metabolism

Abiraterone acetate is hydrolyzed to the active metabolite abiraterone; further metabolized to inactive metabolites abiraterone sulphate and N-oxide abiraterone sulphate via CYP3A4 and SULT2A1

Excretion

Feces (~88%); urine (~5%)

Time to Peak

2 hours (Acharya 2012)

Half-Life Elimination

14.4 to 16.5 hours (Acharya 2012)

Protein Binding

>99%; to albumin and alpha₁-acid glycoprotein

Special Populations: Hepatic Function Impairment

After a single oral 1,000 mg dose (Zytiga), systemic exposure increased ~1.1- and 3.6-fold in subjects with mild and moderate hepatic impairment, respectively. The mean half-life was prolonged to ~18 hours and ~19 hours in subjects with mild and moderate impairment, respectively. Systemic exposure of abiraterone increased by 7- fold and the fraction of free drug increased by 2-fold in subjects with severe baseline hepatic impairment. Mean protein binding was found to be lower in patients with severe hepatic impairment.

Use: Labeled Indications

Prostate cancer, metastatic:

Treatment of metastatic, castration-resistant prostate cancer (in combination with prednisone [Zytiga] or methylprednisolone [Yonsa])

Treatment of metastatic, high-risk castration-sensitive prostate cancer (in combination with prednisone [Zytiga])

Contraindications

Females who are or may become pregnant

Canadian labeling: Additional contraindication (not in the US labeling): Hypersensitivity to abiraterone acetate or any component of the formulation or container

Dosing: Adult

Note: Patients receiving abiraterone should also receive a gonadotropin-releasing hormone (GnRH) analog concurrently (or have had a bilateral orchiectomy). Abiraterone acetate is available in different tablet formulations; use caution when selecting dosage form as dosing and food effects vary between products. The formulations are NOT interchangeable; do not substitute between formulations.

Prostate cancer, metastatic, castration-resistant: Oral:

Zytiga: 1,000 mg once daily (in combination with prednisone 5 mg twice daily) (de Bono 2011; Ryan 2015)

Yonsa (micronized formulation): 500 mg once daily (in combination with methylprednisolone 4 mg twice daily)

Prostate cancer, metastatic, high-risk, castration-sensitive: Oral: Zytiga: 1,000 mg once daily (in combination with prednisone 5 mg once daily) (Fizazi 2017)

or (off-label combination; Zytiga) 1,000 mg once daily (in combination with prednisolone 5 mg once daily) (James 2017)

Dosage adjustment for concomitant strong CYP3A4 inducers: Avoid concomitant strong CYP3A4 inducers during treatment; if a strong CYP3A4 inducer must be administered concurrently, increase the abiraterone frequency to twice daily (eg, from 1,000 mg once daily to 1,000 mg twice daily [Zytiga] or from 500 mg once daily to 500 mg twice daily [Yonsa]). Upon discontinuation of the strong CYP3A4 inducer, reduce abiraterone back to the prior dose and frequency.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

No dosage adjustment necessary.

Dosing: Hepatic Impairment

Hepatic impairment prior to treatment initiation:

Mild (Child-Pugh class A): No dosage adjustment necessary.

Moderate (Child-Pugh class B): 250 mg once daily. Permanently discontinue if ALT and/or AST >5 times the upper limit of normal (ULN) or total bilirubin >3 times ULN occur during treatment in patients with baseline moderate hepatic impairment.

Severe (Child-Pugh class C): Do not use.

Hepatotoxicity during treatment:

ALT and/or AST >5 times ULN or total bilirubin >3 times ULN: Withhold treatment until liver function tests return to baseline or ALT and AST ≤2.5 times ULN and total bilirubin ≤1.5 times ULN, then reinitiate at 750 mg once daily.

Recurrent hepatotoxicity on 750 mg/day: Withhold treatment until liver function tests return to baseline or ALT and AST ≤2.5 times ULN and total bilirubin ≤1.5 times ULN, then reinitiate at 500 mg once daily.

Recurrent hepatotoxicity on 500 mg once daily: Discontinue treatment

ALT >3 times ULN and total bilirubin >2 times ULN (in the absence of biliary obstruction or other contributing cause responsible for concurrent elevation): Permanently discontinue treatment

Dosing: Adjustment for Toxicity

Hepatotoxicity: Refer to Dosing: Hepatic Impairment.

Administration

Note: Abiraterone acetate is available in different tablet formulations; use caution when selecting dosage form as dosing and food effects vary between products. The formulations are NOT interchangeable; do not substitute between formulations.

Oral: Administer abiraterone (Zytiga) orally on an empty stomach, at least 1 hour before and 2 hours after food. No food should be consumed for at least 2 hours before or for at least 1 hour after the abiraterone (Zytiga) dose. Abiraterone micronized (Yonsa) may be administered without regard to food. Swallow tablets whole with water. Do not crush or chew.

Storage

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

Drug Interactions

Amphetamines: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Amphetamines. Monitor therapy

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

Choline C 11: Antiandrogens may diminish the therapeutic effect of Choline C 11. Monitor therapy

CloZAPine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of CloZAPine. Monitor therapy

CYP1A2 Substrates (High risk with Inhibitors): Abiraterone Acetate may increase the serum concentration of CYP1A2 Substrates (High risk with Inhibitors). Monitor therapy

CYP2C8 Substrates (High risk with Inhibitors): Abiraterone Acetate may increase the serum concentration of CYP2C8 Substrates (High risk with Inhibitors). Monitor therapy

CYP2D6 Substrates (High risk with Inhibitors): Abiraterone Acetate may increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors). Management: Avoid concurrent use of abiraterone with CYP2D6 substrates that have a narrow therapeutic index whenever possible. When concurrent use is not avoidable, monitor patients closely for signs/symptoms of toxicity. Consider therapy modification

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

CYP3A4 Inducers (Strong): May decrease the serum concentration of Abiraterone Acetate. Management: Avoid whenever possible. If such a combination cannot be avoided, increase abiraterone acetate dosing frequency from once daily to twice daily during concomitant use. Consider therapy modification

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

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

DOXOrubicin (Conventional): CYP2D6 Inhibitors (Moderate) may increase the serum concentration of DOXOrubicin (Conventional). Management: Seek alternatives to moderate CYP2D6 inhibitors in patients treated with doxorubicin whenever possible. One U.S. manufacturer (Pfizer Inc.) recommends that these combinations be avoided. Consider therapy modification

Eliglustat: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Eliglustat. Management: Reduce the eliglustat dose to 84 mg daily. Avoid use of eliglustat in combination with a moderate CYP2D6 inhibitor and a strong or moderate CYP3A4 inhibitor. 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

Fesoterodine: CYP2D6 Inhibitors may increase serum concentrations of the active metabolite(s) of Fesoterodine. Monitor therapy

Indium 111 Capromab Pendetide: Antiandrogens may diminish the diagnostic effect of Indium 111 Capromab Pendetide. Avoid combination

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

Metoprolol: CYP2D6 Inhibitors may increase the serum concentration of Metoprolol. Management: Consider an alternative for one of the interacting drugs in order to avoid metoprolol toxicity. If the combination must be used, monitor response to metoprolol closely. Metoprolol dose reductions may be necessary. Consider therapy modification

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

Nebivolol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Nebivolol. Monitor therapy

Perhexiline: CYP2D6 Inhibitors may increase the serum concentration of Perhexiline. Management: Consider alternatives to this combination if possible. If combined, monitor for increased perhexiline serum concentrations and toxicities (eg, hypoglycemia, neuropathy, liver dysfunction). Perhexiline dose reductions will likely be required. Consider therapy modification

Pitolisant: May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Combined use of pitolisant with a CYP3A4 substrate that has a narrow therapeutic index should be avoided. Other CYP3A4 substrates should be monitored more closely when used with pitolisant. Consider therapy modification

Radium Ra 223 Dichloride: May enhance the adverse/toxic effect of Abiraterone Acetate. Avoid combination

Rifapentine: May decrease the serum concentration of Abiraterone Acetate. Monitor therapy

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

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

Spironolactone: May diminish the therapeutic effect of Abiraterone Acetate. Monitor therapy

St John's Wort: May decrease the serum concentration 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

Tamoxifen: CYP2D6 Inhibitors (Moderate) may decrease serum concentrations of the active metabolite(s) of Tamoxifen. Specifically, CYP2D6 inhibitors may decrease the metabolic formation of highly potent active metabolites. Management: Consider alternatives with less of an inhibitory effect on CYP2D6 activity when possible. Consider therapy modification

Tamsulosin: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Tamsulosin. Monitor therapy

Thioridazine: CYP2D6 Inhibitors may increase the serum concentration of Thioridazine. Avoid combination

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

TraMADol: CYP2D6 Inhibitors (Moderate) may diminish the therapeutic effect of TraMADol. These CYP2D6 inhibitors may prevent the metabolic conversion of tramadol to its active metabolite that accounts for much of its opioid-like effects. Monitor therapy

Adverse Reactions

Adverse reactions reported for use in combination with a corticosteroid.

>10%:

Cardiovascular: Hypertension (9% to 37%), edema (25% to 27%)

Central nervous system: Fatigue (39%), insomnia (14%)

Endocrine & metabolic: Hypertriglyceridemia (63%), hyperglycemia (57%), hypernatremia (33%), hypokalemia (17% to 30%), hypophosphatemia (24%), hot flash (15% to 22%)

Gastrointestinal: Constipation (23%), diarrhea (18% to 22%), dyspepsia (6% to 11%)

Genitourinary: Urinary tract infection (7% to 12%)

Hematologic & oncologic: Lymphocytopenia (20% to 38%; grades 3/4: 4% to 9%), bruise (13%)

Hepatic: Increased serum alanine aminotransferase (11% to 46%), increased serum aspartate aminotransferase (15% to 37%), increased serum bilirubin (7% to 16%)

Neuromuscular & skeletal: Arthralgia (≤30%), joint swelling (≤30%), myalgia (26%)

Respiratory: Cough (7% to 17%), upper respiratory infection (5% to 13%), dyspnea (12%), nasopharyngitis (11%)

1% to 10%:

Cardiovascular: Cardiac arrhythmia (7%), chest discomfort (≤4%), chest pain (≤4%), cardiac failure (2%)

Central nervous system: Headache (8%), falling (6%)

Dermatologic: Skin rash (8%)

Genitourinary: Hematuria (10%), groin pain (7%), urinary frequency (7%), nocturia (6%)

Neuromuscular & skeletal: Bone fracture (6%)

Miscellaneous: Fever (9%)

<1%, postmarketing, and/or case reports: Acute hepatic failure, adrenocortical insufficiency, fulminant hepatitis, myopathy, pneumonitis, rhabdomyolysis

Warnings/Precautions

Concerns related to adverse effects:

• Adrenocortical insufficiency: Concurrent infection, stress, or interruption of daily corticosteroids is associated with reports of adrenocortical insufficiency. Monitor closely for signs and symptoms of adrenocorticoid insufficiency, which could be masked by adverse events associated with mineralocorticoid excess. Diagnostic testing for adrenal insufficiency may be clinically indicated. Increased corticosteroid doses may be required before, during, and after stress.

• Hepatotoxicity: Severe hepatotoxicity (eg, fulminant hepatitis, acute liver failure, and death) has been reported. Significant increases in liver enzymes (including grade 3 and 4 events) have also been observed (higher likelihood in patients with baseline elevations), generally occurring in the first 3 months of treatment. May require dosage reduction, treatment interruption, and/or discontinuation. ALT, AST, and bilirubin should be monitored prior to treatment, every 2 weeks for 3 months and monthly thereafter; patients with hepatic impairment, elevations in liver function tests, or experiencing hepatotoxicity require more frequent monitoring (see dosage adjustment for hepatic impairment and monitoring parameters). Evaluate liver function promptly with signs or symptoms of hepatotoxicity. The safety of retreatment after significant elevations (ALT or AST ≥20 times the ULN and/or total bilirubin ≥10 times ULN) has not been evaluated.

• Mineralocorticoid excess: Increased mineralocorticoids due to CYP17 inhibition may result in hypertension, hypokalemia, and fluid retention (including grade 3 and 4 events). Monitor at least monthly for hypertension, hypokalemia, and fluid retention (if necessary, control blood pressure and correct hypokalemia prior to and during treatment). Concomitant administration with corticosteroids reduces the incidence and severity of these adverse events.

Disease-related concerns:

• Cardiovascular disease: May cause hypertension, hypokalemia, and fluid retention. Control hypertension and correct hypokalemia prior to and during treatment. Use with caution in patients with cardiovascular disease, particularly with heart failure, recent MI, or ventricular arrhythmia. Patients with left ventricular ejection fraction (LVEF) <50% or NYHA class II, III, or IV heart failure were excluded from clinical trials. Monitor at least monthly for hypertension, hypokalemia, and fluid retention.

• Hepatic impairment: Do not use in patients with preexisting severe hepatic impairment (Child-Pugh class C); dosage reduction is recommended in patients with baseline moderate 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:

• Tablet formulations: Abiraterone acetate is available in different tablet formulations (the conventional formulation [Zytiga] and a micronized [fine particle] formulation [Yonsa]); use caution when selecting dosage form as dosing and food effects vary between products. The formulations are NOT interchangeable; do not substitute between formulations.

Other warnings/precautions:

• Food: Abiraterone (Zytiga) must be administered on an empty stomach (administer at least 1 hour before and 2 hours after any food); abiraterone AUC (exposure) may be increased up to 10-fold if administered with a meal. Abiraterone micronized (Yonsa) may be administered without regard to food.

Monitoring Parameters

ALT, AST, and bilirubin prior to treatment, every 2 weeks for 3 months and monthly thereafter; if baseline moderate hepatic impairment (Child-Pugh class B), monitor ALT, AST, and bilirubin prior to treatment, weekly for the first month, every 2 weeks for 2 months then monthly thereafter. If hepatotoxicity develops during treatment (and only after therapy is interrupted and liver function tests have returned to safe levels), monitor ALT, AST, and bilirubin every 2 weeks for 3 months and monthly thereafter. Monitoring of testosterone levels is not necessary. Serum potassium (prior to treatment and at least monthly).

Monitor for signs and symptoms of adrenocorticoid insufficiency; if clinically indicated, consider appropriate diagnostics to confirm adrenal insufficiency. Monitor blood pressure and for fluid retention (prior to treatment and at least monthly). Monitor adherence.

Pregnancy Considerations

Based on the mechanism of action and adverse effects observed in animal reproduction studies, abiraterone may cause fetal harm or fetal loss if administered during pregnancy. Abiraterone is not indicated for use in females and is specifically contraindicated in females who are or may become pregnant. Abiraterone is available in uncoated and film-coated tablets and in micronized tablets; the manufacturer recommends females who are or may become pregnant wear gloves if handling uncoated tablets, micronized tablets, or tablets that are broken, crushed, or damaged. NIOSH recommends single gloving for administration of hazardous intact oral tablets (NIOSH 2016).

Male patients with female partners of reproductive potential should use effective contraception during treatment and for 3 weeks after the last abiraterone dose. Abiraterone may impair reproductive function and fertility in males of reproductive potential.

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 flushing, muscle pain, joint pain, joint edema, heartburn, cough, diarrhea, constipation, common cold symptoms, nausea, or vomiting. Have patient report immediately to prescriber signs of electrolyte problems (mood changes, confusion, muscle pain or weakness, abnormal heartbeat, seizures, lack of appetite, or severe nausea or vomiting), signs of liver problems (dark urine, fatigue, lack of appetite, nausea, abdominal pain, light-colored stools, vomiting, or jaundice), signs of adrenal gland problems (severe nausea, vomiting, severe dizziness, passing out, muscle weakness, severe fatigue, mood changes, lack of appetite, or weight loss), signs of a urinary tract infection (hematuria, burning or painful urination, polyuria, fever, lower abdominal pain, or pelvic pain), signs of high blood sugar (confusion, fatigue, increased thirst, increased hunger, polyuria, flushing, fast breathing, or breath that smells like fruit), severe headache, severe dizziness, passing out, vision changes, tachycardia, shortness of breath, excessive weight gain, edema, severe loss of strength and energy, or bruising (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 health care 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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