Drug Interactions

Drug Interactions

Drug interactions occur when one drug in the body affects another drug that aperson is taking. The interaction can take many forms, and may be helpful orharmful. Drugs that are known to interact are sometimes given together in orderto have a positive effect.

What is the information for this topic?

Drug interactions can cause serious problems. The more drugs a person takes,the more likely a drug interaction is. Drug interactions can occur with manytypes of substances. These include prescription medications, over-the-countermedications, herbal remedies, andvitamins. Homeopathic remedies and recreational drugs, such asalcohol, tobacco, and illegal drugs, can also interact.

Effects of drug interactions

Drug interactions can happen in the following ways:

  • Drug A increases the effect of drug B. This can make drug B more likely tocause side effects or toxic effects. For example, ketoconazole, a medicationused to treat fungal infections, can increase the levels of a blood-thinningmedication called warfarin.
  • Drug A decreases the effect of drug B. This may make drug B less effectiveor even ineffective. For example, an antibiotic called rifampin can cause birth control pills to be broken downtoo quickly. A woman taking both of these medications risks becomingpregnant.
  • Drug A and drug B have additive effects, which can be helpful or harmful.For example, both aspirin and warfarin thin the blood. Insome situations, taking both medications may be beneficial. But in other cases,it may lead to an increased risk of serious bleeding.
  • Drug A and drug B have opposite effects. This may cause an unpredictableresponse. For example, people on medication to control high blood pressure must becareful if they take ephedrine for nasal congestion because itcan raise blood pressure.
  • How drugs interact

    There are several ways in which drug interactions can take place. Drug A mightinterfere with the way drug B is absorbed into the bloodstream through thegut. Or drug A might block the metabolism, or the breakdown, of drug B by theliver. Drug A might block drug B from being eliminated from the urine. Drugscan also interact at the cell level. For example, one drug may push the otherdrug off the cell and make it less effective. There are a number of other kindsof interactions.


    When a new medication is prescribed, a person should tell his or herhealthcare provider what other drugs he or she is taking. To avoid seriousdrug interactions, it’s important tomention medications that have been prescribed by other healthcare providers.A person cannot afford to be quietabout taking birth control pills,over-the-counter medications, herbalremedies and complementary therapies, or illegal drugs. All drugs andsubstances are important to mention.

    The American Society of Anesthesiologists recently issued a warning about thepotential side effects and interactions of herbal remedies with medications used before,during, and after surgery. The group recommends discontinuing allherbal supplements at least two weeks before planned surgery.

    An individual who takes over-the-counter medications should read the warninglabels on the package. Sometimes, important drug interactions are listedon the box. Those who take prescription medications should ask their healthcareproviders before taking new medications or herbal remedies. A pharmacist can be consulted when buyingover-the-counter medications to be sure that they do not interact withprescription medications.

    A good way to help reduce the risk of drug interactions is to get allprescriptions filled at the same pharmacy. That way the pharmacist will have acomplete record of all the medications the person is taking. The pharmacist canmake sure there are no potentially dangerous interactions. This is especiallyimportant for people who are treated by more than one healthcare provider.

    There are hundreds of possible drug interactions. The list grows longer everyyear. It’s wise to check for possible drug interactions before any newsubstance is taken.

    Article type: xmedgeneral