The interaction can take many forms, and may be helpful or harmful. Drugs that are known to interact are sometimes given together in order to have a positive effect. Drug interactions can cause serious problems. The more drugs a person takes, the more likely a drug interaction is.
Drug interactions can occur with many types of substances.
Homeopathic remedies and recreational drugs, such as alcohol , tobacco , and illegal drugs, can also interact. For example, ketoconazole, a medication used to treat fungal infections, can increase the levels of a blood-thinning medication called warfarin. For example, an antibiotic called rifampin can cause birth control pills to be broken down too quickly. A woman taking both of these medications risks becoming pregnant . For example, both aspirin and warfarin thin the blood.