Grapefruit and grapefruit juice are associated with a number of drug interactions. Over 85 different medications are known to interact with grapefruit, and over half of these may cause serious side effects. For people living with diabetes, this could potentially mean medications used for high blood pressure, high cholesterol or depression. Read on to learn more about potential interactions you should be aware of.
Why does grapefruit interact with some medications?
Here’s what happens: Grapefruit contains furanocoumarins, a type of organic chemical compound that inhibits the efficacy of an important enzyme, called CYP3A4. This enzyme normally helps your body process the medication you take, balancing out how much of it goes into your bloodstream. Because furanocoumarins hinder this enzyme, larger amounts of the drug persist in your bloodstream and medication levels can grow toxic in the body.
And it doesn’t take much. One whole grapefruit or one glass of grapefruit juice is enough to alter how these medications affect you. It’s not just grapefruit, either. Other citrus fruits such as Seville oranges (often used in marmalade), limes and pomelos also contain furanocoumarins, but none of these have been as widely studied as grapefruit.
What does this mean for people with diabetes?
Currently, two drugs used to treat diabetes – repaglinide (GlucoNorm®) and saxagliptin (Onglyza®) – have been shown to interact with grapefruit. Their respective product monographs state the plasma concentrations of the drug rose after grapefruit was consumed. Saxagliptin is part of a class of medications called DPP-4 inhibitors. Other DPP-4 inhibitors have not been thoroughly studied but may also be affected by grapefruit. If you are taking any of these medications, you should speak with your healthcare team about whether and when you should consume grapefruit.
Metformin, SLGT-2 inhibitors (examples include empagliflozin, dapagliflozin), GLP-1 receptor agonists (examples include semaglutide, liraglutide), and insulin are generally safe to take with grapefruit. These drugs are not metabolized by CYP3A4, so grapefruit does not affect them.
Other medications that interact with grapefruit
Other drugs that people with diabetes may be taking also have some interactivity with grapefruit. Since people with type 2 diabetes are at increased risk of heart disease (including high cholesterol, high blood pressure and atrial fibrillation), it’s important to know whether you should avoid eating grapefruit or drinking grapefruit juice, in the event that you’re taking medications for any of these, or the other conditions listed below.
- Statins (cholesterol drugs): examples include lovastatin (Mevacor®), atorvastatin (Lipitor®), simvastatin (Zocor®), simvastatin/ezetimibe combination
- Interaction: Grapefruit can increase blood levels of these statins, raising the risk of muscle toxicity, known as rhabdomyolysis
- Safer alternatives include: rosuvastatin (Crestor®), fluvastatin (Lescol®), pravastatin (Pravachol®),
- Calcium channel blockers (blood pressure drugs): examples include amlodipine (Norvasc®), diltiazem (Cardiazem®, Tiazac®), felodipine (Plendil®), nifedipine XL (Adalat XL®), verapamil (Isoptin SR®, Verelan®)
- Interaction: Increased drug levels may cause hypotension, dizziness or edema
- Antiarrhythmics (atrial fibrillation drugs): examples include amiodarone (Cordarone®), disopyramide (Norpace®)
- Interaction: Increased risk of QT prolongation, arrhythmia and other side effects.
- Erectile dysfunction drugs: examples include sildenafil (Viagra®), tadalafil (Cialis®)
- Interaction: Increased risk of side effects such as headache, flushing or low blood pressure.
- Psychiatric medications: examples include buspirone (BuSpar®), triazolam (Halcion®), carbamazepine (Tegretol®), diazepam (Valium®), midazolam (Versed®), sertraline (Zoloft®)
- Anticoagulants and antiplatelets (used for stroke or heart attack prevention): examples include rivaroxaban (Xarelto®), apixaban (Eliquis®)
You can view a comprehensive list of medications that interact with grapefruit here.
Be sure to speak with your doctor or pharmacist about your drug regimen, and if you’re taking any medications that may interact with grapefruit.
