Grapefruit And Drug Interactions: What To Avoid

Overview

Grapefruit, a hybrid of the sweet orange and the pomelo is a common type of fruit easily found in supermarkets. It is delicious and juicy, not to say nutritious. It is packed with numerous vitamins and minerals essential for various body functions. Whether served on its own or added to salads or smoothies, grapefruit has been a popular choice for a healthy diet. 

However, you may need to be cautious if you are taking certain types of medicines. Grapefruit can interfere with the way your body processes the medicine. This can increase the risks of experiencing unwanted effects from the medicine or affect the effectiveness of the medicine. You can usually find the warning from the patient information leaflet. If you are unsure about it, it is always best to speak to your GP or pharmacist. Never stop taking your medicine by yourself.

How does grapefruit affect your medicine?

In normal conditions, after the medicine is swallowed through the stomach (absorption), it will be distributed (distribution) in the blood throughout your body, broken down (metabolism) and removed (elimination) from your body. 

Certain types of medications are broken down with the help of an essential enzyme called, cytochrome P450 (CYP) 3A4, in the liver and small intestine. This process is important to ease the removal of medicine in the blood, thereby preventing too much medicine from staying in your body that could otherwise cause harmful side effects. Grapefruit can stop the functioning of the enzyme CYP450 and prevent the medicine from being broken down.¹ In this case, the medicine will stay in your body for longer, increasing your chances of having side effects. Therefore, you are advised to avoid eating grapefruit or drinking grapefruit juice if you are on certain types of medicine.

What medicines are affected by grapefruit?

Here are some common examples of medicines that grapefruit can cause problems with:

Statins 

Statins, such as simvastatin and atorvastatin, are medicines for lowering cholesterol. Statins are commonly prescribed for people with high blood cholesterol or people with heart disease for the prevention of heart attacks and strokes.

If you are on simvastatin, you should avoid eating grapefruit or drinking grapefruit juice. Grapefruit can increase the amount of the medicine in your blood, leading to an increased risk of getting side effects. In serious cases, you will get rhabdomyolysis, a breakdown of muscle tissue that can lead to kidney failure and death although it is rare.²

For atorvastatin, problems will only occur if you intake large quantities of grapefruit or grapefruit juice (more than 1.2 litres daily). You will be fine if you drink grapefruit juice in moderate quantities occasionally.³

Calcium channel blockers 

Calcium channel blockers, such as amlodipine, felodipine and nifedipine, are used for the treatment of high blood pressure (hypertension) and coronary heart disease.

Same as statins, grapefruit juice can increase the amount of the medicine in your blood. This can affect your blood pressure and heart rate from the effects of the medicine.⁴ You may experience symptoms, such as headache and dizziness.

Warfarin 

Warfarin is (a type of anticoagulant/blood thinner) commonly prescribed to people at high risk of getting blood clots for the prevention of heart attacks and strokes. If you drink grapefruit juice while taking warfarin, you will be more likely to experience bleeding.⁵ 

Alternatively, other newer blood-thinning drugs (anticoagulants), such as rivaroxaban, dabigatran and apixaban, are safer to use with grapefruit juice.⁶

Antiplatelet medicines 

Antiplatelet medicines, such as clopidogrel and ticagrelor, are used for the prevention of heart attacks and strokes.

You are advised not to drink grapefruit juice while taking clopidogrel. Grapefruit juice can reduce the effectiveness of the medicine for the prevention of blood clotting.⁷ 

On the other hand, grapefruit juice can increase the effects of ticagrelor. However, this can increase your chances of excessive bleeding.⁸ Therefore, you need to avoid drinking grapefruit juice if you are on ticagrelor.

Alternatively, other options, e.g., dipyridamole or low-dose aspirin, are safe to be taken with grapefruit juice.

Immunosuppressants 

Immunosuppressants, such as ciclosporin, sirolimus and tacrolimus, moderate your immune system. They are commonly prescribed to people with rheumatoid arthritis and people who receive transplantation. You should check with your GP or pharmacist if you consume grapefruit with the medicine.⁹

Entocort

Entocort is the medicine for the treatment of Crohn’s disease. The active ingredient, budesonide, interacts with grapefruit. The level of budesonide in your blood will increase if you consume grapefruit juice.⁹

Cytotoxic medicines

Cytotoxic medicines are commonly used to treat cancers. Some cytotoxic medicines interact with grapefruit. Make sure your GP or pharmacist knows if you regularly consume grapefruit during cancer treatment.¹⁰

In general, grapefruit may either increase the effects of the medicine or cause the medicine to be less effective. However, some cases could be lenient. It is safe to drink an occasional glass of grapefruit juice. Most importantly, you should always read the patient information leaflet carefully. If you are in doubt, always reach out to your GP for advice. They can even prescribe an alternative medicine that does not interact with grapefruit according to your needs.

FAQs

Where can I find the warning of grapefruit and drug interactions from the package of my medicine?

A statement of warning is usually stated on the patient information leaflet under a section of “medicine with food and drink”, and the relevant wordings are printed in bold. Also, you may find the safety warnings on the medicine label printed from your pharmacy. If you are in doubt, do not hesitate to ask your GP or pharmacist.

What would happen if I drank grapefruit juice while taking a medicine that interacts with grapefruit?

The effects you might experience could vary based on the medicine and related side effects. In case you accidentally consume grapefruit juice, while taking your medicine, do not stop taking your medicine yourself and remember to let your GP or pharmacist know as soon as possible. If you experience severe side effects, call 111 or go to A&E.

Can I consume grapefruit juice at a different time to avoid interaction with my medicine?

You are advised not to do so if you are warned about your medicine interacting with grapefruit. The effects of grapefruit on your medicine can last for over 24 hours.¹¹ Drinking grapefruit juice at a different time during the day cannot prevent the interaction. In some cases, you might be allowed to drink small quantities of grapefruit juice with your medicine. Always consult with your GP or pharmacist before you do so.

What other types of fruits or fruit juices should I avoid?

If your medicine interacts with grapefruit, you should be cautious when consuming the Seville orange (often used in marmalades), pomelo and tangelos. These fruits may have similar effects to grapefruit.

For other types of fruits or fruit juices, it is safe to consume with your medicine unless it is specified on the patient information leaflet.

Always check the food or drink labels closely. Some flavoured foods or drinks may contain grapefruit extract.

If you are in doubt, always check with your GP or pharmacist.

Summary

While grapefruit is a tasty and nutritious fruit, caution should be taken if you are warned that your medicine interacts with grapefruit. Grapefruit can interfere with the enzyme to break down your medicine. As a result, your medicine will stay in your body for longer and cause unwanted effects. Therefore, you are advised to avoid eating grapefruit or drinking grapefruit juice while taking medicine interacting with grapefruit. In some cases, you might be allowed to consume small quantities of grapefruit juice. However, you should discuss this with your GP or pharmacist in the first place. If you regularly consume grapefruit in your diet, speak to your GP and they can prescribe an alternative medicine for you. You should never stop taking your medicine yourself in any situation without consent from your GP. If you are unsure of anything, do speak to your GP or pharmacist for advice.

• Ask your GP or pharmacist if you can consume grapefruit while taking the medicine prescribed.
• Avoid eating grapefruit or drinking grapefruit juice at any time if you are warned your medicine interacts with grapefruit. 
• Make sure your GP knows if you regularly consume grapefruit in your diet. Other medicines that do not interact with grapefruit are available.
• Always check the labels on all types of food and drinks. Some flavoured foods and drinks might contain grapefruit extract. These should also be avoided if you are taking medicines interacting with grapefruit.
• You should not stop taking your medicine yourself even when you accidentally consume grapefruit with your medicine. Make sure to let your GP know as soon as possible. If you experience severe symptoms, call 111 or go to A&E.