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Avoiding Drug Interactions

“What medications are you currently taking?”

That’s one of the first questions you’re likely to hear when visiting a doctor. It’s important to be prepared to answer with a complete list of your prescription medications, nonprescription medications, vitamins, minerals, and any herbal supplements you are taking.

If some medications are taken at the same time, they can cause harmful interactions. If you take several different medications, see more than one doctor, or have certain health conditions, then you, your physicians, and your pharmacist need to be aware of all the medications you take to avoid risking further health problems.

Drug interactions can cause unexpected side effects. Some drug combinations can weaken the effectiveness of your medications, while others might increase the action of a particular drug.

Taking the time to learn about drug interactions could be critical to your health. You can reduce the risk of potentially harmful drug interactions with a little bit of knowledge and common sense. Drug interactions fall into four broad categories:

1. Drug-drug interactions. These occur when two or more drugs react with each other. Drug-drug interactions can cause unexpected side effects. For example, alcohol is actually a type of drug known as a central nervous system depressant. It can be deadly when mixed with other drugs of that type, including many medications prescribed to reduce anxiety or to help people sleep.

2. Drug-food interactions. These result from drugs reacting with foods or beverages. Grapefruit or grapefruit juice can interact with different types of medications—including some blood pressure and cholesterol-lowering drugs—raising the risks of potentially harmful side effects.

3. Drug-supplement interactions. These occur when herbal supplements and vitamins interact with drug-metabolizing enzymes. For example, ginseng can increase blood pressure. When taken along with the blood-thinning warfarin, this interaction can cause bleeding episodes.

4. Drug-condition interactions. These may occur when an existing medical condition makes certain drugs potentially harmful. For example, if you have hypertension, you could experience an increase in blood pressure if you take a nasal decongestant.

Avoiding drug interactions
“One of the most common paths to a problem with drug interactions is not using one single pharmacist to monitor all of your drugs,” says Frank Romanelli, associate professor of Pharmacy Practice and Science at the University of Kentucky’s College of Pharmacy. “There are so many different medications available right now for various diseases that it’s critical for people to know their pharmacist and to rely on their expertise.”

Talk with your doctor or pharmacist before taking any new prescription or over-the-counter medication. Some good questions to ask are: Can I take this medication with other drugs? Should I avoid certain foods, beverages, or other products? What are possible drug interaction signs I should know about? How will the drug work in my body?

Thoroughly read the labels of all over-the-counter and prescription medicines, vitamins, and dietary supplements. Pay close attention to dosage instructions, potential side effects, and other warnings.

Keep a record listing your over-the-counter and prescription drugs and take it with you when you visit your doctor or pharmacist. Use one pharmacy for all your medication purchases. Only take medication that has been specifically prescribed for you by your physician.

“Patients should realize that all medications, whether they are prescription or over-the-counter, involve potential interactions and side effects,” Romanelli says. “By learning more about their medications, patients will feel more empowered over their own medication taking and health.”


Blood pressure medicine:
decongestants (pseudoephedrine, phenylephrine)

Diabetes drugs:
certain diuretics

Cholesterol medications:
grapefruit juice

Heart disease:
certain older antidepressants

Blood thinners:
aspirin and other non-steroidal
anti-inflammatory drugs (e.g., naproxen, ibuprofen)
certain antibiotics
some vitamin supplements (E, K)

older antidepressants

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