Drug Interactions

What is a drug interaction?

A drug interaction is a change in the effect of a drug caused by some other substance. The effect of the drug may be blocked or enhanced, or the usual side effects may change. It is important to remember that alcohol and tobacco, as well as prescription and nonprescription medicines, can be involved in drug interactions. Vitamins, natural remedies, and certain foods may also interact with drugs.

There are many different types of drug interactions. Sometimes, drug interactions are helpful. For example, drug combinations may be prescribed that allow lower doses of 1 or more medicines to be used. This can reduce the chance of side effects.

How does it occur?

Drug interactions fall into 2 broad categories:

• Drug/drug interactions occur when 2 or more drugs react with each other. For example, one drug might decrease the effectiveness of another drug. Some medicines are more likely to interact with other drugs and cause serious problems, such as severe bleeding or heart rhythm problems. Two common examples of such drugs are the blood thinner warfarin (Coumadin) and the heart medicine digoxin (Lanoxin).
• Drug/food interactions result from drugs reacting with foods or beverages. For example, drinking alcohol while taking some drugs, such as sedatives or antidepressants, may cause you to feel tired or it may slow your reactions. It can even cause you to stop breathing. These effects can make driving a car or operating machinery dangerous. Grapefruit juice affects the way some medicines work and may increase the risk of side effects.

Drugs may also work differently if you have an existing medical condition such as diabetes, heart disease, or asthma. Some drugs may be harmful for people with certain conditions. For example, taking a nasal decongestant can raise your blood pressure, which may be harmful if you already have high blood pressure.

Any time you take a new medicine, there is a possibility it will interact with other medicines you take. To avoid problems caused by drug interactions, your healthcare provider and pharmacist need to be aware of all the medicines, herbal remedies, vitamins, and other supplements that you take, especially if you:

• take several different medicines
• see more than one healthcare provider
• buy your medicines at more than 1 pharmacy
• have certain health problems, such as heart disease, diabetes, liver, or kidney disease.

Keep a list of your current medicines and dosages with you at all times. Providers can then check the list to see if any drug interactions might occur.

What can I do to prevent drug interactions?

Before taking a new medicine, ask your healthcare provider or pharmacist these questions:

• Can I take it with the other drugs I am taking?
• Should I avoid certain foods, beverages, vitamins, or herbs?
• What are possible signs of a drug interaction I should know about?