Background: In an effort to promote the improved tolerability of combination antiretroviral therapy (ART) regimens for treatment of HIV, the Zambian Ministry of Health adopted the WHO recommendation of using low dose efavirenz (efavirenz 400mg or EFV400) as part of the alternative first line ARV regimens due to significantly fewer efavirenz -associated adverse events compared to the conventional efavirenz 600mg dose (EFV600). Following the dolutegravir (DTG) safety concerns in early pregnancy from the Botswana Tsepamo study and the favorable tolerability, virologic efficacy and CYP2B6 pharmacogenetics of EFV400 in pregnant women living with HIV (WLWH) from Uganda and the United Kingdom, EFV400 combined with tenofovir disoproxil fumarate (300mg) and lamivudine (300mg) was recommended as the preferred regimen in pregnancy in Zambia.
Methods: We evaluated maternal virologic suppression and infant HIV outcomes among WLWH on EFV based ART with documented maternal viral load at/near time of delivery and infant HIV status in twelve (12) high volume antenatal clinics within urban Lusaka. The primary outcomes were maternal virologic suppression (viral load < 1000 copies/mL) and vertical transmission rate based on infant HIV DNA PCRs.
Results: Two hundred and eighty-seven (287) mother-infant pairs were analyzed with 271 (94%) women having initiated or transitioned to EFV400 during pregnancy with 16 (6%) remaining on EFV600 with a mean age of 30 years (95% CI:29.97, 31.57). Forty percent (40%) started ART during pregnancy with a median duration on EFV400 of 4.83 months (95%:CI 4.28, 5.37). Maternal viral suppression at delivery was 92% (95% CI: 89,96) among those receiving EFV400 and 88% among those receiving EFV600. HIV DNA PCR was positive in 2 (0.7%) of the HIV exposed infants, with 3 (1.04%) non-viable outcomes and 0 fetal abnormalities.
Conclusions: Our findings show that the 400mg dose of EFV was associated with high levels of maternal viral suppression during pregnancy. This rate was higher than the previously reported suppression rates of 75% on EFV600 in the same Zambian population and this could be due to the improved tolerability of the lower EFV (400mg) dose. These findings support the routine use of EFV 400mg in pregnancy while providing a favorable alternative option to dolutegravir.