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Preventing Drug Interactions

Gail Carlson, MPH, Ph.D., Continuing Medical Education, School of Medicine, University of Missouri-Columbia


Drug interactions are serious business. Interactions can reduce the effectiveness of drugs; the drugs don't work as well as they should. At other times, drug interactions lead to serious complications such as drowsiness, slowed reactions, stomach upset, liver damage, dizziness, light-headedness, irregular heartbeat, and a sudden rise in blood pressure.

There are three types of drug interactions:

  • Drug-food interactions result from medicines reacting with foods or beverages. Vitamin and mineral supplements can also interact with medicines. Some drugs work best when taken with food, while others should be taken on an empty stomach.
  • Drug-condition interactions take place when an existing medical condition makes certain medicines potentially harmful. For example, people with heart disease, thyroid disease, or diabetes should not take nasal decongestants without first checking with a doctor.
  • Drug-drug interactions occur when two or more medicines react with each other. For example, mixing a sedative and an antihistamine can slow your reactions and make operating machinery dangerous. Drug-drug interactions can result in severe symptoms and may be misdiagnosed as a new illness.

Pay attention to how your body responds to medicines and be sensitive to side effects. Don't assume that these side effects are a normal. You can help prevent some interactions by becoming a wiser health consumer.

  • Read labels and package inserts carefully, pay particular attention to the "Warning" and "Precaution" Sections. Review this information each time you get a refill; guidelines for use change as more is learned.
  • Brownbag your medications. You are the only person who knows everything you are taking. The next time you have an appointment with your health care provider take all your medications with you. Include medications prescribed by other doctors and any over-the-counter drugs. Don't forget any supplements or vitamins you are taking. Don't assume that your doctor knows everything you are taking. Make sure you ask your provider about possible interactions. 
  • Ask your doctor, nurse, or pharmacist to help you work out a daily schedule for taking your medication. Some interactions may be avoided by taking the medications at different times. Keep a list of your medications in your medicine cabinet and a copy in your wallet or pocketbook. 
  • Before you take a new medication ask:


  • What is the name of this medication? 

  • Can I take this with other medicines? 

  • Should I avoid certain foods, beverages, or other products? 

  • What should I look for, what kinds of reactions are possible? 

  • How does this medicine work in the body? 

  • What other kinds of precautions are necessary? 

  • Is there additional written information that I could read about the medicine?


  • Go to one pharmacy for all your prescriptions. Good record keeping can reduce the risk of interactions. Many pharmacies have their records computerized. 
  • Don't use outdated drugs, drugs that appear to have been tampered with, or drugs given to you for another condition. 
  • Know ahead of time what to do if anything goes wrong when taking medicines. Know whom to contact and how to reach him or her. Keep the phone numbers of your doctors on hand -- next to the telephone and on a card you carry in your wallet or purse.

Medications are playing an increasingly important role in our health care. They are improving health outcomes and quality of life. To make the best use of these medications know how and when to take your medications, be alert to side effects, and periodically ask your provider if a certain medication is still needed.



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Last Updated 05/05/2009