Drug Interactions and Your Health

It is important to understand the medications you are taking to ensure they are working best for you and to prevent potentially dangerous health consequences. As Ontario’s pharmacy regulator, with a mandate to serve and protect the public and a vision to drive quality and safe pharmacy care, we feel it is important that you are aware of what you can do to avoid drug interactions and how your pharmacist can help.

Drug Interaction Definition and Types of Drug Interactions

A drug interaction is when one or more of your medications affect how the other medications you’re taking work. Below we outline three types of drug interactions: drug-drug interactions, drug-food interactions and drug-condition interactions (1).

A drug-drug interaction is when two or more drugs work together to produce a reaction and sometimes unexpected side effects. For example, antibiotics can increase or decrease effects of other medication used to treat cardiovascular disease and diabetes.

A drug-food interaction is when one or more drugs react with food or a beverage. For example, calcium-rich foods like milk, yogurt, and cheese can interfere with certain antibiotics and prevent the antibiotic from being absorbed in your body.

A drug-condition interaction is when a when one or more drugs cause a reaction with an existing medical condition. For example, if you have hypertension and take certain nasal decongestants, your blood pressure may spike.

6 Tips to Avoid a Drug Interaction

Here are some tips to help avoid drug interactions:

1. Speak with your pharmacist

Your pharmacist has extensive knowledge in pharmacology, including how drugs work, their side effects, interactions, and more, and can help you learn about the medications you’re taking, how to take them, what to expect and what to avoid.

Your pharmacist can also collaborate with your physician and other members of your healthcare team about adjusting your medication therapy and finding an alternate medicine that may be more effective for you. When speaking with your pharmacist, be sure to tell them about any nonprescription medicines and food supplements that you take.

ISMP Canada, the Canadian Patient Safety Institute, Patients for Patient Safety Canada, the Canadian Pharmacists Association, and the Canadian Society for Hospital Pharmacists have collaborated to develop a set of five questions to help patients and caregivers start a conversation about medications to improve communications with their health care provider. We outline these five questions in the box below, as well as share some other questions we’ve proposed that you may wish to ask your pharmacist or physician about to prevent drug interactions and potential harm.

2. Be aware of what each medication you’re taking is used to treat

When talking with your pharmacist, it is helpful to communicate the condition your physician prescribed each medication for. This makes it easy for your pharmacist to immediately spot potential negative interactions.

3. Be aware of the best way to take your medication

Is it best to take your medication with water? Milk? Juice? Should it be taken with food or on an empty stomach? Knowing the answers to these questions will help negate potential negative effects and can increase the effectiveness of the medication.

4. Be mindful of alcohol and/ or tobacco consumption

Combining medication with alcohol and/ or tobacco can interact with your medication (2). Taking your medicine and drinking alcohol can increase the side effects of particular drugs and can increase the chance of complications, such as liver problems and stomach bleeds, which can occur when three or more alcohol drinks are consumed in combination with pain reducers and anti-inflammatory medications (3).

5. Read labels carefully

Make sure you carefully read the prescription labels on your prescribed and over-the-counter medication which often will alert/remind you of potential drug interactions. As well, be sure to read the labels of food or beverage products you may consume with your medication.

6. Keep a list of your medications and how to take them

Keeping a centralized list of all your medications, including supplements and natural food products, and instructions on how to take each one can go a long way in preventing harm from a drug interaction.

As medication therapy experts, pharmacists are highly qualified to provide you with valuable information and advice about drug interactions, taking your medicines safely, and maximizing your health outcomes. By understanding the types of drug interactions, what you can do to avoid them, and key questions to ask those on your healthcare team, you can rest assured that you’re equipped with important knowledge to take your medications safely and effectively.

Key Questions to Ask About Your Medication

The questions listed below are valuable in preventing drug interactions and harm from your mediation and should be considered when speaking to your pharmacist, physician, or nurse (4).

    1. Changes – Have any medications been added, stopped, or changed, and why?
    2. Continue – What medications do I need to keep taking, and why?
    3. Proper Use – How do I take my medications, and for how long?
    4. Monitor – How will I know if my medication is working, and what side effects do I watch for?
    5. Follow-Up – Do I need any tests and when do I book my next visit?

Other questions you can ask your pharmacist or physician to prevent drug interactions and potential harm include:

    • Can I take this medication with the other drugs I’m taking?
    • Which foods, beverages, or other products should I avoid?
    • How does the medication work in my system?
    • What are possible drug interaction signs I should look out for?
    • Can you help me understand the information on the medication label?
    • Is there a resource you might recommend for me to read more about the medication or my condition?
  1. U.S. Food & Drug Administration. Drug Interactions: What You Should Know. September 2013. Retrieved at https://www.fda.gov/drugs/resources-you-drugs/drug-interactions-what-you-should-know
  2. Aging in Canada. Alcohol and Medication Interactions. January 2005. Retrieved at http://www.agingincanada.ca/Seniors%20Alcohol/1f3.htm
  3. Ontario Pharmacists Association. To Eat or Not to Eat: Avoiding Food-Drug Interactions. November 2014. Retrieved at https://www.opatoday.com/professional/news/blog/avoiding_food_drug_interactions
  4. ISMP Canada. 5 Questions to Ask About Your Medications. Retrieved at https://www.ismp-canada.org/medrec/5questions.htm