What is a drug interaction?

Certain medications should not be taken in combination with other prescription or over-the-counter (OTC) drugs and others might require that you avoid certain foods or beverages. If your healthcare provider has prescribed a new medication it is important that you tell him or her about all the prescription and OTC medications you are currently taking and ask about possible drug interactions.

Drug interactions can cause unwanted or harmful side effects or potentially make your drug less effective or increase the potency of a medication. Discuss possible drug interactions with your provider or pharmacist before you begin taking a new medication and be sure to carefully read the label of any other OTC or prescription drugs you take. This is especially important for people who see several different providers, have multiple conditions, or are already taking more than one medication. Taking the time to learn about drug interactions is one of the best ways to reduce the risk of potentially harmful interactions. According to the FDA drug interactions fall into three broad categories:

  • Drug-drug interactions: These types of interactions result when two or more drugs react with each other, causing an unexpected side effect. For example, if you take a drug to help you sleep (a sedative) and a drug to alleviate your allergies (an antihistamine) your reaction times could be slowed, making driving a car or operating machinery dangerous.
  • Drug-food/beverage interactions: These types of interactions occur when drugs react with certain foods or beverages. For example, mixing alcohol with some drugs may cause you to feel tired or slow your reactions.
  • Drug-condition interactions: This may occur if you have an existing medical condition that could make certain drugs harmful. For example, those who have high blood pressure might experience an unwanted reaction while taking a nasal decongestant.