ART Adverse Events

Drug-Drug Interactions: Focus on Hormonal Contraceptives

There are significant drug-drug interactions between ARVs and numerous other medications. These interactions may result in therapeutically significant increases or decreases in levels of either ARVs or interacting drugs. It is important to consider potential interactions carefully before any ARVs or other medication is prescribed.

An important example of drug-drug interactions is that of ARVs with oral hormonal contraceptives. PIs and NNRTIs may affect the hepatic metabolism of oral contraceptive agents. Depending on the specific antiretroviral medication, this may result in:

• Higher levels of ethinyl estradiol or norethindrone, possibly resulting in increases in contraceptive side effects such as nausea, vomiting, and breakthrough bleeding
• Lower levels of ethinyl estradiol or norethindrone, possibly resulting in contraceptive failure (pregnancy)

It is also important to understand that oral contraceptive medication may lower levels of some antiretrovirals, including fosamprenavir, ritonavir, and tipranavir, possibly resulting in subtherapeutic dosing and risk of virologic failure.

As an alternative to oral contraception, depomedroxyprogesterone acetate (DMPA) offers several advantages; however, its side effects also must be considered.

Pregnancy, whether resulting from adverse drug-drug interactions, ineffective contraceptive use, or a desire to become pregnant, commonly occurs among both behaviorally and perinatally HIV-infected adolescent women. When starting patients on ART, care providers should be aware of which medications are contraindicated during pregnancy and avoid using those drugs for adolescent women who may be using unreliable contraception.

In addition, there are significant drug-drug interactions between antiretrovirals and numerous other medications. It is important to consider these carefully before any new medication is prescribed.