PBPK Modeling to Recommend Nevirapine Dosing in HIV and HIV-TB Co-infected Patients: Leveraging Enzyme Auto-Induction, Drug Interactions, and Ethnic Variability.

Nevirapine, primarily metabolized by CYP2B6 and CYP3A4, exhibits enzyme auto-induction and significant ethnic variability in its pharmacokinetics (PK). These complexities are further exacerbated in HIV-TB co-infected patients, where nevirapine is often co-administered with rifampicin/isoniazid-based anti-tuberculosis (TB) therapies. Rifampicin, a strong CYP3A4 inducer and moderate CYP2B6 inducer, and isoniazid, a moderate CYP3A4 inhibitor, create intricate drug interactions that challenge optimal nevirapine dosing strategies, leading to clinical uncertainty and debate. We developed a physiologically based pharmacokinetic (PBPK) model for nevirapine that integrates auto-induction, drug interactions, and ethnic variability. The model successfully captured the time-dependent PK of nevirapine across Caucasian, African, and Asian populations, with and without rifampicin/isoniazid co-administration. Simulations revealed that the standard nevirapine regimen (200 mg QD lead-in, 200 mg BID maintenance) was appropriate for Caucasian and African HIV patients but required adjustment to 150 mg QD lead-in and 150 mg BID maintenance for Asians to minimize toxicity. In HIV-TB co-infected patients, nevirapine co-administration with rifampicin/isoniazid was unsuitable for Caucasians due to sub-therapeutic levels. For Africans, an increased regimen (200 mg QD lead-in, 300 mg BID maintenance) was recommended, while drug interactions did not alter the reduced dosing recommendation of nevirapine for Asians. Our findings underscore the necessity of incorporating ethnic variability and drug interaction profiles into nevirapine dosing strategies to optimize therapeutic efficacy and safety in HIV and HIV-TB co-infected patients.