Overview
11 DESCRIPTION Abiraterone acetate USP, the active ingredient of abiraterone acetate tablets, USP is the acetyl ester of abiraterone. Abiraterone is an inhibitor of CYP17 (17α-hydroxylase/C17,20-lyase). Each abiraterone acetate tablet, USP contains 250 mg or 500 mg of abiraterone acetate USP.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Abiraterone acetate is converted in vivo to abiraterone, an androgen biosynthesis inhibitor, that inhibits 17 α-hydroxylase/C17,20-lyase (CYP17). This enzyme is expressed in testicular, adrenal, and prostatic tumor tissues and is required for androgen biosynthesis. CYP17 catalyzes two sequential reactions: 1) the conversion of pregnenolone and progesterone to their 17α-hydroxy derivatives by 17α-hydroxylase activity and 2) the subsequent formation of dehydroepiandrosterone (DHEA) and androstenedione, respectively, by C17, 20 lyase activity. DHEA and androstenedione are androgens and are precursors of testosterone.
Indications
- 1 INDICATIONS AND USAGE Abiraterone acetate tablets are indicated in combination with prednisone for the treatment of patients with Metastatic castration-resistant prostate cancer (CRPC) Metastatic high-risk castration-sensitive prostate cancer (CSPC) Abiraterone acetate tablet is a CYP17 inhibitor indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (CRPC). ( 1) metastatic high-risk castration-sensitive prostate cancer (CSPC). ( 1 )
Common Doses
- 000 mg
- 5 mg
- 250 mg
- 500 mg
Dosage
2 DOSAGE AND ADMINISTRATION Metastatic castration-resistant prostate cancer: • Abiraterone acetate tablets 1,000 mg orally once daily with prednisone 5 mg orally twice daily. ( 2.1 ) Metastatic castration-sensitive prostate cancer: • Abiraterone acetate tablets 1,000 mg orally once daily with prednisone 5 mg orally once daily. ( 2.2 ) Patients receiving abiraterone acetate tablets should also receive a gonadotropin-releasing hormone (GnRH) analog concurrently or should have had bilateral orchiectomy. Abiraterone acetate tablets must be taken as a single dose once daily on an empty stomach.
Contraindications
- 4 CONTRAINDICATIONS None. None ( 4 )
Side Effects
- 6 ADVERSE REACTIONS The following are discussed in more detail in other sections of the labeling: Hypokalemia, Fluid Retention, and Cardiovascular Adverse Reactions due to Mineralocorticoid Excess [see Warnings and Precautions ( 5.1 )]. Adrenocortical Insufficiency [see Warnings and Precautions ( 5.2 )]. Hepatotoxicity [see Warnings and Precautions ( 5.3 )]. Increased Fractures and Mortality in Combination with Radium Ra 223 Dichloride [see Warnings and Precautions (5.4) ].
Interactions
- 7 DRUG INTERACTIONS CYP3A4 Inducers: Avoid concomitant strong CYP3A4 inducers during abiraterone acetate treatment. If a strong CYP3A4 inducer must be co-administered, increase the abiraterone acetate dosing frequency. ( 2.5 , 7.1 ) CYP2D6 Substrates: Avoid co-administration of abiraterone acetate with CYP2D6 substrates that have a narrow therapeutic index. If an alternative treatment cannot be used, exercise caution and consider a dose reduction of the concomitant CYP2D6 substrate. ( 7.2 ) 7.