Drug Interactions between Aptiom and atorvastatin

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of atorvastatin and its active metabolites, all of which are substrates of the isoenzyme. When atorvastatin (40 mg/day) was coadministered for 28 days with the potent CYP450 3A4 inducer phenytoin (4 mg/kg/day) in healthy volunteers (n=44), atorvastatin peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by an average of 24% and 54%, respectively. The Cmax of two active metabolites, 2-hydroxy- and 4-hydroxyatorvastatin, also decreased by an average of 22% and 52%, respectively, while AUC decreased by an average of 53% and 44%, respectively. Consistent with the observed pharmacokinetic interaction, there have been isolated reports of reduced efficacy of atorvastatin in the presence of phenytoin, followed by improved cholesterol levels after discontinuation of phenytoin. In another study, coadministration of the mixed CYP450 3A4 inducer/inhibitor efavirenz (600 mg once daily for 15 days) with atorvastatin (10 mg daily during the last 4 days of efavirenz) in 14 healthy volunteers resulted in median decreases of 43% in atorvastatin AUC and 34% in total active atorvastatin (parent drug + active metabolites) AUC. However, the median LDL decrease was not significantly different during coadministration with efavirenz compared to atorvastatin administered alone (-29 versus -22, respectively). Atorvastatin did not affect the AUC of efavirenz. In a study of patients with non-small cell lung cancer receiving the CYP450 3A4 inducer bexarotene (400 mg/m2 orally once a day) plus either paclitaxel/carboplatin or cisplatin/vinorelbine chemotherapy, treatment with atorvastatin or fenofibrate was given to manage bexarotene-induced hyperlipidemia. Investigators reported that bexarotene decreased mean atorvastatin systemic exposure (dose-corrected AUC) by approximately 50%, whereas atorvastatin had no significant effect on bexarotene plasma concentrations. In 16 study subjects administered etravirine with atorvastatin 40 mg once a day, atorvastatin AUC decreased by 37%, while Cmax and AUC of 2-hydroxy-atorvastatin increased by 76% and 27%, respectively. Atorvastatin did not significantly affect the pharmacokinetics of etravirine.

MANAGEMENT: The potential for diminished pharmacologic effects of atorvastatin should be considered during coadministration with CYP450 3A4 inducers. Alternative agents with no or minimal CYP450 3A4 induction potential are recommended whenever possible. Otherwise, pharmacologic response to atorvastatin should be closely monitored, and the dosage adjusted as necessary. A statin that is not metabolized by CYP450 3A4 such as fluvastatin, pitavastatin, pravastatin, or rosuvastatin may also be substituted for atorvastatin when used with certain enzyme inducers.

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