Understanding drug interactions

A drug interaction is a reaction between two (or more) drugs (called a drug-drug interaction) or between a drug and a food or beverage (called a drug-food interaction). An existing medical condition can make certain drugs potentially harmful (called a drug-condition interaction). For example, taking a nasal decongestant if you have high blood pressure may cause an unwanted reaction.

Medicines help us feel better and stay healthy. But drug interactions can cause problems by reducing or increasing the action of a medicine or causing adverse (unwanted) side effects.

Are drug interactions a problem for people with HIV?

Treatment with HIV medicines (called antiretroviral therapy or ART) helps people with HIV live longer, healthier lives. But drug interactions, especially drug-drug interactions, can complicate HIV treatment.

Drug-drug interactions between HIV medicines are common, and may reduce or increase the concentration of an HIV medicine in the blood. This can make the affected HIV medicine less effective, or increase levels that also increase the risk of side effects. 

Drug-drug interactions between HIV medicines and other medicines may make hormonal birth control less effective. Women using hormonal contraceptives may need to use an additional or different method of birth control to prevent pregnancy.

Can drug-food interactions and drug-condition interactions affect people with HIV?

Yes, the use of HIV medicines can lead to both drug-food interactions and drug-condition interactions.

Food or beverages can affect the absorption of some HIV medicines and increase or reduce the concentration of the medicine in the blood. Depending on the HIV medicine, the change in concentration may be helpful or harmful. Instructions for HIV medicines affected by food specify whether to take the medicine with or without food. (HIV medicines not affected by food can be taken with or without food.)

Pregnancy is a condition that can affect how the body processes HIV medicines.

Because of pregnancy-related changes, dosing of an HIV medicine may change during different stages of pregnancy. But pregnant women should always consult with their health care providers before making any changes to their HIV regimens.

How can I avoid drug interactions?

Tell your health care provider about all prescription and non-prescription medicines you are taking or plan to take. Also tell your health care provider about any vitamins, nutritional supplements, and herbal products you take.

Before taking a medicine, ask your health care provider or pharmacist these questions:

  • How should I take the medicine?
  • While taking the medicine, should I avoid any other medicines or certain foods or beverages?
  • Can I take this medicine safely with the other medicines that I am taking? Are there any possible drug interactions I should know about? What are the signs of those drug interactions?
  • In the case of a drug interaction, what should I do? 

Take medicines according to your health care provider’s instructions. Drug labels and package inserts include important information about possible drug interactions. Tell your health care provider if you have any side effect that bothers you or that does not go away.

Learn more about drug interactions at aidsinfo.nih.gov/drugs and fda.gov.