CYP3A inhibitors: Co-administration of 400 mg once daily ketoconazole, a strong CYP3A, P-gp and BCRP inhibitor, for 7 days in 11 previously treated patients with NHL increased Venetoclax Cmax by 2.3-fold and AUC by 6.4-fold. Co-administration of 50 mg once daily ritonavir, a strong CYP3A and P-gp inhibitor, for 14 days in 6 healthy subjects increased Venetoclax Cmax by 2.4-fold and AUC by 7.9-fold. Co-administration of Venetoclax with other strong CYP3A4 inhibitors is predicted to increase Venetoclax AUC by on average 5.8- to 7.8-fold. Concomitant use of Venetoclax with strong CYP3A inhibitors (e.g., itraconazole, ketoconazole, posaconazole, voriconazole, clarithromycin, ritonavir) at initiation and during the dose-titration phase is contraindicated due to increased risk for TLS.At initiation and during the dose-titration phase, concomitant use of Venetoclax with moderate CYP3A inhibitors (e.g., ciprofloxacin, diltiazem, erythromycin, fluconazole, verapamil) should be avoided. Alternative treatments should be considered. If a moderate CYP3A inhibitor must be used, the initiation dose of Venetoclax and the doses for the titration phase should be reduced by at least 50%. Patients should be monitored more closely for signs and symptoms of TLS.For patients who have completed the dose-titration phase and are on a steady daily dose of Venetoclax, the Venetoclax dose should be reduced by 50% when used concomitantly with moderate CYP3A inhibitors and by 75% when used concomitantly with strong CYP3A inhibitors. Patients should be monitored more closely for signs of toxicities and the dose may need to be further adjusted. The Venetoclax dose that was used prior to initiating the CYP3A inhibitor should be resumed 2 to 3 days after discontinuation of the inhibitor. Grapefruit products, Seville oranges, and starfruit (carambola) should be avoided during treatment with Venetoclax as they contain inhibitors of CYP3A.P-gp and BCRP inhibitors: Venetoclax is a substrate for P-gp and BCRP , Co-administration of a 600 mg single dose of rifampin, a P-gp inhibitor, in 11 healthy subjects increased Venetoclax Cmax by 106% and AUC by 78%. Concomitant use of Venetoclax with P-gp and BCRP inhibitors at initiation and during the dose-titration phase should be avoided; if a P-gp and BCRP inhibitor must be used, patients should be monitored closely for signs of toxicities.CYP3A inducers: Co-administration of 600 mg once daily rifampin, a strong CYP3A inducer, for 13 days in 10 healthy subjects decreased Venetoclax Cmax by 42% and AUC°° by 71%. Concomitant use of Venetoclax with strong CYP3A inducers (e.g., carbamazepine, phenytoin, rifampin) or moderate CYP3A inducers (e.g., bosentan, efavirenz, etravirine, modafinil, nafcillin) should be avoided. Alternative treatments with less CYP3A induction should be considered. Preparations containing St. John's wort are contraindicated during treatment with Venetoclax, as efficacy may be reduced.