Interactions

Most medicines interact with some other drugs, affecting the way one or both works.

An interaction can alter the amount of one or both drugs in your body. This can mean you don't have enough of a drug present in your blood for it to work properly, risking the development of resistance. Or it can mean that you have too much of a drug, increasing the chance of side-effects developing.

Interactions are one of the reasons why it makes very good sense for your HIV doctor (and any other medical professional who prescribes you medicines) to know about all the medicines, vitamins, supplements or any recreational drugs you might be taking.

There are interactions between some anti-HIV drugs and everyday, over-the-counter medicines, that it’s important to be aware of. It always makes good sense to read the leaflet that comes with all medicines as this will include information about possible drug interactions.

Anti-indigestion remedies

Some anti-HIV drugs can interact with drugs used to treat indigestion, acid reflux and stomach ulcers. This is a particularly the case with atazanavir (Reyataz), but may also be the case with other protease inhibitors as well.

Drugs called proton pump inhibitors, such as omeprazole (Losec), and histamine-2 (H2) antagonists (blockers), for example, ranitidine (Zantac), can lower levels of atazanavir.

If you need to take indigestion remedies and are taking a protease inhibitor, it makes good sense to speak to a member of your HIV healthcare team about your options. For example, it’s recommended to leave at least ten hours between taking a dose of an H2 antagonist such as Zantac and taking your atazanavir.

Antihistamines

Some anti-HIV drugs can also interact with some antihistamines – types of medicines taken for hay fever and allergies.

Protease inhibitors and NNRTIs are the types of anti-HIV drug most likely to interact with antihistamines. There’s a risk of an interaction between anti-HIV drugs and antihistamines that contain fexofenadine and loratadine. You should not take antihistamines that contain astemizole or terfenadine if you are taking HIV treatment. (Terfenadine has been withdrawn for general use in the UK.)

If you are buying them over the counter from a chemist, then it’s good to know that antihistamines that contain cetirizine don’t interact with anti-HIV drugs.

It makes good sense to speak to a member of your HIV team if you regularly need to take antihistamines. Your doctor should be able to prescribe you some that are safe to take with your anti-HIV drugs.

Cold and flu remedies

Cold and flu remedies contain painkillers, normally paracetamol. There is no interaction between paracetamol and anti-HIV drugs, but paracetamol should be used carefully if you have any liver problems.

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.