Birato 250 Drug Interactions

Drugs that Inhibit or Induce CYP3A4 Enzymes: Based on in vitro data, abiraterone acetate is a substrate of CYP3A4.
In a dedicated drug interaction trial, coadministration of rifampin, a strong CYP3A4 inducer, decreased exposure of abiraterone by 55%. Avoid concomitant strong CYP3A4 inducers during abiraterone acetate treatment. If a strong CYP3A4 inducer must be coadministered, increase the abiraterone acetate dosing frequency [see Dose Modification Guidelines for Strong CYP3A4 Inducers under Dosage & Administration and Pharmacology: Pharmacokinetics under Actions].
In a dedicated drug interaction trial, coadministration of ketoconazole, a strong inhibitor of CYP3A4, had no clinically meaningful effect on the pharmacokinetics of abiraterone [see Pharmacology: Pharmacokinetics under Actions].
Effects of Abiraterone on Drug Metabolizing Enzymes: Abiraterone acetate is an inhibitor of the hepatic drug-metabolizing enzymes CYP2D6 and CYP2C8. In a CYP2D6 drug-drug interaction trial, the C_max and AUC of dextromethorphan (CYP2D6 substrate) were increased 2.8- and 2.9-fold, respectively, when dextromethorphan was given with abiraterone acetate 1,000 mg daily and prednisone 5 mg twice daily. Avoid coadministration of abiraterone acetate with substrates of CYP2D6 with a narrow therapeutic index (e.g., thioridazine). If alternative treatments cannot be used, consider a dose reduction of the concomitant CYP2D6 substrate drug [see Pharmacology: Pharmacokinetics under Actions].
In a CYP2C8 drug-drug interaction trial in healthy subjects, the AUC of pioglitazone (CYP2C8 substrate) was increased by 46% when pioglitazone was given together with a single dose of 1,000 mg abiraterone acetate. Therefore, patients should be monitored closely for signs of toxicity related to a CYP2C8 substrate with a narrow therapeutic index if used concomitantly with abiraterone acetate [see Pharmacology: Pharmacokinetics under Actions].