Health Encyclopedia

A Must-Know Guide to Drug-Drug Interactions

Drug-drug interactions can occur when you are taking more than 1 medication or drug. One medication can interfere with or alter the effects of 1 or more of the other medications you take.

Such interactions can be dangerous because they can alter the way 1 or both of the drugs act in the body. They can also cause unexpected side effects. Interactions can increase the action of medications, decrease their actions, or result in a different and less predictable effect from the combination of drugs.

A common misperception is that only prescription medications have the potential to interact with each other. But over-the-counter medicines also may result in drug-drug interactions when combined with prescription medications or with other over-the-counter medicines, vitamins, or herbal products.

The following information can help you avoid drug-drug interactions.

Common interactions

Not all drug-drug interactions are alike. Sometimes when drugs interact, the overall effect of 1 or more of the drugs may be greater than desired.

For example, both aspirin and blood thinners, such as warfarin or Coumadin, help prevent blood clots from forming. Using these medications together, however, may cause excessive bleeding.

With other combinations of medicine, the effectiveness of the drugs may be reduced. For example, certain antacids can prevent many medicines from being absorbed into the bloodstream. If this happens, the medicine may not work as well or may not work at all.

Keep a list

If you experience any reaction that seems out of the ordinary after taking any medication, consult your health care provider or local pharmacist and make him or her aware of all of the medicines and remedies you're taking. Some herbal supplements can add to the risk of drug-drug interactions.

In fact, herbal products and supplements don’t have to be tested to prove they work well and are safe, and may be dangerous for individuals with certain health problems. Always ask your doctor or pharmacist about possible interactions if you are taking any herbal remedies or supplements. The American Academy of Family Physicians recommends that you should be especially cautious about using herbal health products or supplements if you take any of the following types of drugs:

  • Drugs to treat depression, anxiety or other psychiatric problems

  • Antiseizure drugs

  • Blood thinners

  • Blood pressure medicine

  • Heart medicine

  • Drugs to treat diabetes

  • Cancer drugs

In the case of a serious reaction, call 911 for emergency medical treatment.

The following steps can help you and your family avoid drug-drug interactions:

  • Read the label. Be sure you are taking the correct dosage. Know what side effects can occur.

  • Know the risks. Make sure you know the benefits and the potential risks of medications you take. Look specifically for the section called "warnings" on the labels of over-the-counter medicines.

  • Ask questions. Talk to your health care provider or pharmacist before taking any new medication. Ask whether it's safe to take the new medicine with other medications, vitamins or herbal products you already take regularly or even occasionally.

  • Keep a list of all the drugs you take and share it with your doctors and your pharmacist.

  • Pick a pharmacy. Use 1 pharmacy for all of your family's medication needs. Doing so allows your pharmacist to look for and help you avoid drug-drug interactions.



Medical Reviewers:

  • Russell, Nikki, RN, BSN
  • Stock, Christopher J., PharmD, BCPP