When one drug alters the effect of another drug—intensifying the side effects or producing new side effects or making the drug less effective—this is known as a drug interaction. It is important to choose HIV medications that do not interact with other drugs you take.
Talk to your doctor(s) and pharmacist about all the different drugs you’re taking—including prescription drugs, over-the-counter drugs, street drugs, herbal and nutritional supplements—so they can advise you about possible interactions. In some cases, there are drugs that cannot be used together. In other cases, it may be possible to use certain drugs together provided you make certain adjustments (for example, change the time when you take one of them).