According to the United States Department of Agriculture, Americans consume 164 million gallons of grapefruit juice every year, a statistic that may be of concern to doctors and pharmacists. In the early 1990s, a research team in Canada discovered a dangerous interaction between grapefruit juice and the heart medication Plendil (felodipine).
During the past 15 years, doctors and pharmacists have learned that more than 50 prescription and over-the-counter drugs are affected by grapefruit juice, including some of the most commonly prescribed medications. This list includes a number of medications used to treat high cholesterol, high blood pressure, depression, pain, erectile dysfunction, and allergies.
How Does Grapefruit Juice Affect Medications?
The cells that line your small intestine contain an enzyme called CYP3A4. This enzyme helps break down dozens of medications. Certain substances in grapefruit juice inhibit CYP3A4 and hence allow more of a medication to enter your blood stream.
Having too much medicine in your blood could result in serious side effects or a drug overdose. For example, if you take a statin (such as Lipitor) to help lower cholesterol, having too much of it in your body could increase your risk for a serious muscle disorder or liver damage.
Which Medications Interact with Grapefruit Juice?
Most medications do not interact with grapefruit juice. However, grapefruit juice does have an effect on more than 50 drugs, including some medications for the treatment of:
- Abnormal heart rhythm
- Asthma and COPD
- Blood clots
- BPH (enlarged prostate)
- Erectile dysfunction
- Heart disease
- High blood pressure
- High cholesterol
- Hormonal conditions
- Infection-viral, bacterial and fungal
How Do I Know if Grapefruit Juice Is Safe for Me?
Grapefruit juice does not affect all of the medications used to treat the conditions listed above. Check with your healthcare provider or pharmacist to find out about your specific drug.
All new medications are tested for drug interactions, including grapefruit juice, before they are approved by the U.S. Food and Drug Administration (FDA). When you order medications in the mail or pick them up at your local pharmacy, you should receive a patient information sheet, which will let you know if your drug is affected by grapefruit juice. Some pharmacies may also put a warning label on your medication bottle. If you are not sure, ask the pharmacist.
What Can Happen if I Continue to Drink Grapefruit Juice?
It is important to know that grapefruit juice and medication can be a dangerous mix! Your risk of serious side effects depends on how much grapefruit juice you drink, your age, and the type and dose of your medications. Additionally, the amount of the CYP3A4 enzyme in the intestine varies from person to person.
Older adults who drink a lot of grapefruit juice are more likely to have medication side effects. And, certain classes of drugs, such as the statins (used to treat high cholesterol) and calcium-channel blockers (used to treat high blood pressure) are more likely to produce severe side effects when taken with grapefruit juice.
Do Oranges and Other Citrus Fruits Interact with Drugs?
Oranges, lemons and limes are less likely to interact with medications. However, tangelos, related to the grapefruit, and Seville oranges affect the same enzyme as grapefruit juice. Seville oranges are often used to make orange marmalade, and so be mindful when selecting this spread for your toast.
How Can I Avoid Problems with Grapefruit Juice?
- Before starting a new medication, talk to your healthcare provider and pharmacist about potential drug interactions.
- Carefully read the patient information sheet given to you at the pharmacy. If you do not receive one, then ask for it.
- Check the warning labels on your medication bottle before leaving the pharmacy. If grapefruit juice is not mentioned, ask the pharmacist if you can safely drink it.
- Make a list of all your medications, including prescription drugs and over-the-counter drugs. Review the list with your healthcare providers and pharmacist to look for possible drug interactions.
If there is a chance that grapefruit juice will interact with your medication, you may want to start your morning with a glass of orange juice or cranberry juice.
Got a Question? Ask Dr. Mike!
Abramowicz M. Drug interactions with grapefruit juice. Medical Letter on Drugs and Therapeutics, 2004;46:2–4.
Kane GC, Lipsky JJ. Drug-grapefruit juice interactions. Mayo Clin Proc. 2000;75:933-942
Saito M, et al. Undesirable effects of citrus juice on the pharmacokinetics of drugs: focus on recent studies. Drug Saf. 2005;28:677-94.