An interaction between two drugs means that the two drugs interact with each other in the body and reduce the concentration of one or both.
Antiretroviral therapy (ART) medicines used to treat HIV/AIDS do interact with other medications. This can reduce the efficacy of the ART medicines taken for other health conditions because interactions can cause the blood levels of the medicines to fall. There can even be serious side effects or toxic reactions.
HIV drug interaction issue has become an increasingly difficult situation for HIV physicians. Newer drugs are being introduced and their interactions have to be researched as well. Many a time, the physician has to predict drugs adverse to HIV medicines without any supporting data.
If you are taking medicines for some other health condition, any vitamin supplements, any over the counter drugs, even any herbal or alternative treatments, you must inform your physician about your drug profile.
He has a choice of medications for HIV treatment and can accordingly place you on the preferred combination, which will not interact with your existing medicines.
It is difficult to remember all drug interactions, but it is important to note that PIs (particularly ritonavir), NNRTIs, and cobicistat very commonly interact with other medications.
Similarly, if you are on HIV medications, and have to take treatment for some other health ailment, however minor, you must inform the doctor about your HIV treatment.
Broadly, HIV drugs can interact with the other medicines given for the following conditions.
- Age-related cardiac conditions
- Metabolic diseases
- Bone diseases
- Acid reflux
- Cold and flu
- Hormonal contraceptives in women
- Tuberculosis such as Rifampicin
- Hepatitis C drug such as Harvoni
- Erectile dysfunction
- Psychiatric illnesses
Some drugs, which can interact with HIV antiretroviral therapy medications:
- Viagra interacts with HIV medications belonging to the class of Protease Inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). This results in an increase of Viagra blood levels, which can cause side effects.
- Drugs given for asthma
- Drugs given for heartburn such as omeprazole and ranitidine. A time interval of at least 10 hours is sometimes advised between taking the two drugs.
- Magnesium and Aluminum containing antacids given for indigestion
- Statins used to control elevated cholesterol and other lipid levels.
- Rifampicin used in the treatment of tuberculosis.
- Herbal and alternative medicines too can interact with HIV medicines. For example St. John’s wort, an herbal medicine used to treat depression, lowers the levels of PIs and NNRTI class of HIV medications.
- Garlic supplements
- Milk thistle is a plant whose seeds are used to treat liver disorders
- Inhalers and nasal sprays, which contain fluticasone and salmeterol can cause serious side effects when used along with HIV medicines.
- Avoid recreational drugs such as ecstasy, cocaine, heroin, morphine, cannabis.
Drug interactions with anti-HIV ART drugs can be classified as those with a definite evidence of interaction, those with a distinctive probability and those that may be possible. Here is a poweroint presentation:
Definitive Drug interactions with HIV drugs
These are the interactions with a high level of evidence, clinical importance is clear, and there is a consensus. Common definitive interactions with HIV medications include:
- Certain combinations of HIV drugs (e.g., certain PIs or integrase inhibitors with NNRTIs, maraviroc with PIs or NNRTIs, tenofovir with atazanavir)
- Rifamycins and PIs, NNRTIs, cobicistat, or maraviroc
- Statins with PIs or cobicistat
- Erectile dysfunction agents and PIs or cobicistat
- Methadone and certain PIs or NNRTIs
- Fluticasone and PIs or cobicistat
Apparent and acceptable drug interactions
- Antidepressants and PIs or NNRTIs
- Oral contraceptives and PIs or cobicistat
- Warfarin and PIs, NNRTIs, or cobicistat
- Proton pump inhibitors (PPIs) or H-2 blockers and atazanavir or rilpivirine
- Polyvalent cations (e.g., calcium, iron, cation-containing antacids) and integrase inhibitors
- Certain antifungal agents and PIs, NNRTIs, or cobicistat (except in the case of voriconazole, for which definite information on interactions is available)
- Certain antiepileptic medications and PIs, NNRTIs, or cobicistat
Possible drug interactions
Possible drug interactions are those with only theoretical evidence. These include:
- Herbal products and PIs, NNRTIs, or cobicistat (except in the case of St. John’s wort, for which definite information on interactions is available)
- Antidiabetic medications and PIs or NNRTIs
- Antipsychotic agents and PIs, NNRTIs, or cobicistat