Pharmacokinetics and Drug-Drug Interactions of Isoniazid and Efavirenz in Pregnant Women Living With HIV in High TB Incidence Settings: Importance of Genotyping

The World Health Organization guidelines recommend that individuals living with HIV receive >= 6 months of isoniazid preventive therapy, including pregnant women. Yet, plasma isoniazid exposure during pregnancy, in the antiretroviral therapy era, has not been well-described. We investigated pregnancy-induced and pharmacogenetic-associated pharmacokinetic changes and drug-drug interactions between isoniazid and efavirenz in pregnant women. Eight hundred forty-seven women received isoniazid for 28 weeks, either during pregnancy or at 12 weeks postpartum, and 786 women received efavirenz. After adjusting forNAT2andCYP2B6genotype and weight, pregnancy increased isoniazid and efavirenz clearance by 26% and 15%, respectively. Isoniazid decreased efavirenz clearance by 7% inCYP2B6normal metabolizers and 13% in slow and intermediate metabolizers. Overall, both isoniazid and efavirenz exposures were reduced during pregnancy, but the main determinants of drug concentration wereNAT2andCYP2B6genotypes, which resulted in a five-fold difference for both drugs between rapid and slow metabolizers.

Automated summary

The study found that pregnancy increased the clearance of isoniazid and efavirenz, while isoniazid decreased the clearance of efavirenz. NAT2 and CYP2B6 genotypes were the main determinants of drug concentration.