A Must-Know Guide to Drug-Drug Interactions

Drug-drug interactions occur when one drug interacts or interferes with another drug.

Such interactions are dangerous because they can alter the way one or both of the drugs act in the body. They can also cause unexpected side effects.

"A common misperception is that only prescription medications have the potential to interact with each other," says Steve Clement, R.Ph., a pharmacist at Copper Bend Pharmacy in Belleville, Ill., and a spokesman for the American Pharmaceutical Association. "But the truth is, 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 two drugs interact, the overall effect of one or both of the drugs may be greater than desired.

For example, both aspirin and blood thinners such as warfarin -- taken to protect against heart attack -- help prevent blood clots from forming. Using these medications together, however, may cause excessive bleeding.

With other combinations of medicine, the effectiveness of one or both of the drugs may be reduced. 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.

Some of the more common symptoms of drug-drug interactions include nausea or upset stomach, headache, heartburn and dizziness.

Keep a list

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

"No one knows precisely how many Americans regularly use herbal products, and the products aren't subject to the same requirements as over-the-counter medications," says Mr. Clement. "However, some of the most popular remedies can interact with both prescription and over-the-counter 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. If you don't, you may take an incorrect dosage or overlook potential side effects.

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