Pharmacokinetic and pharmacodynamic drug interactions between antiretrovirals and oral contraceptives

More than 50 % of women living with HIV in low- and middle-income countries are of reproductive age, but there are limitations to the administration of oral contraception for HIV-infected women receiving antiretroviral therapy due to drug-drug interactions caused by metabolism via the cytochrome P450 isoenzymes and glucuronidation. However, with the development of newer antiretrovirals that use alternative metabolic pathways, options for contraception in HIV-positive women are increasing. This paper aims to review the literature on the pharmacokinetics and pharmacodynamics of oral hormonal contraceptives when given with antiretroviral agents, including those currently used in developed countries, older ones that might still be used in salvage regimens, or those used in resource-limited settings, as well as newer drugs. Nucleos(t)ide reverse transcriptase inhibitors (NRTIs), the usual backbone to most combined antiretroviral treatments (cARTs) are characterised by a low potential for drug-drug interactions with oral contraceptives. On the other hand non-NRTIs (NNRTIs) and protease inhibitors (PIs) may interact with oral contraceptives. Of the NNRTIs, efavirenz and nevirapine have been demonstrated to cause drug-drug interactions; however, etravirine and rilpivirine appear safe to use without dose adjustment. PIs boosted with ritonavir are not recommended to be used with oral contraceptives, with the exception of boosted atazanavir which should be used with doses of at least 35 µg of estrogen. Maraviroc, an entry inhibitor, is safe for co-administration with oral contraceptives, as are the integrase inhibitors (INIs) raltegravir and dolutegravir. However, the INI elvitegravir, which is given in combination with cobicistat, requires a dose of estrogen of at least 30 µg. Despite the growing evidence in this field, data are still lacking in terms of large cohort studies, randomised trials and correlations to real clinical outcomes, such as pregnancy rates, in women on antiretrovirals and hormonal contraception.