The Grapefruit Effect: A Risk You Need to Know About

Have you heard of the “grapefruit effect”? Alarmingly, grapefruit can adversely affect more than 85 different medications. It can either increase or decrease the impact of a drug on your system, and that’s not ok.

Health Canada writes that consuming sour oranges, like a Seville, and tangelos (a grapefruit hybrid) may have similar effects, while other citruses are believed to be safe with respect to drug interactions.

How Does it Work?

The enzyme CYP3A4, found mainly in the liver and intestine, is responsible for oxidising small foreign molecules found in the body, such as toxins and medications, and works to remove them from your system. In doing so, it regulates the impact of many oral medications. 

However, when grapefruit is introduced into the system, it interferes with the way in which CYP3A4 metabolizes the medication by either intensifying or weakening the effect of the drug.  The effect of grapefruit on your medication can persist for up to 72 hours. Intravenous drugs are metabolized differently, and therefore should not have any reaction to grapefruit.

Learn more about the importance of keeping track of your medications and health trends with The Health Insider’s article: Keeping Your Medical Record Updated.

Adverse and Possibly Deadly Effects

Medications are dispensed to patients in very specific dosages and are accompanied by specific instructions to prevent unintended outcomes. When the level of a medication in your blood is suddenly increased, not only can it cause you to experience more side effects, it can also lead to accidentally overdosing on your prescription.

The Canadian Medical Association Journal (CMAJ) lists the following potentially deadly outcomes resulting from the interaction between grapefruit and certain medications:  

• Torsade de pointes. A very fast heart rhythm of 150-300 beats per minute.
• Complete heart block. Interruption of electrical signals in the heart causing a slow pulse or no pulse.
• Rhabdomyolysis. Muscles break down leading to muscle death. Muscle fibres circulate through circulation system and kidneys, possibly causing kidney damage. 
• Nephrotoxicity. Also known as renal toxicity. Rapid deterioration of kidney function which can lead to the inability to pass urine or waste.
• Myelotoxicity. Bone marrow doesn’t produce enough blood cells or platelets which increases your risk for many illnesses.
• Venous thrombosis. Blood clot(s) develop in a large vein and can cause many complications.

Commonly Affected Medications

Drugs.com lists medications that are known to interact with grapefruit, though it’s not a complete list as drugs are continuously tested.

Not included on this list due to inconsistent research, grapefruit can also interact with some SSRIs (especially sertraline) and antipsychotics.

Alternative Fruits

Many people simply choose to stay away from grapefruits due to the possibility of having it interact with a prescribed medication.

For most people, apples, oranges, and grapes are healthy and tasty alternatives to grapefruit. However, it should be noted that some medications, like certain antihistamines or blood pressure medications, still interact even with these fruits as well. Pomegranate juice is generally safe, except for people on certain breast cancer treatments. 

Always ask your doctor or pharmacist about this possible interaction when starting a new oral medication or before introducing the fruit into your diet. Even one glass of grapefruit juice can cause adverse effects while on certain drugs.

In this age of increasing consumer and patient awareness, it’s best not to rely solely on your doctor to know the answer. If you’re consuming grapefruit or other types of citrus, always check online (i.e. drugs.com) or head to your local pharmacy for expert advice. Your doctor doesn’t know your day-to-day life, so you must take charge for your own health.

~ Read more from The Health Insider ~

• 5 Disruptive Healthcare Innovations for Canadians in 2025
• Ignored Risk: Bone Scans For People Over 50
• Losing Your Sense of Smell; Why It Matters And What To Do

The information provided on TheHealthInsider.ca is for educational purposes only and does not substitute for professional medical advice. TheHealthInsider.ca advises consulting a medical professional or healthcare provider when seeking medical advice, diagnoses, or treatment.