Grapefruit & Medication Interactions

How it happens

Many drugs are broken down with the help of an enzyme called CYP3A4 in the small intestine. The FDA says grapefruit juice can block that enzyme, so more of the drug enters the blood and stays in the body longer. The result can be too much drug and more side effects. [1] The amount of the enzyme varies from person to person, so grapefruit may affect people differently even on the same drug. [1]

The effect can also go the other way. The FDA says grapefruit juice can reduce how much fexofenadine (an allergy medicine) enters the blood, by affecting proteins called drug transporters, and that the fexofenadine label says not to take it with fruit juices. [1]

Examples named by the FDA

These are the FDA's examples of types of drugs that grapefruit juice can cause problems with. They are examples, not a full list.

Source for the table: [1]

The FDA gives one example of what can go wrong: with certain statins, too much of the drug may stay in the body, increasing the risk of liver and muscle damage that can lead to kidney failure. [1]

Not every medicine in a class

The FDA says grapefruit juice does not affect all the drugs in the categories above, and that the severity differs by person, drug and amount of juice. [1] So do not assume a whole class is affected, and do not assume yours is not.

What the NHS leaflets say for named medicines

The NHS in England gives plain instructions for specific medicines. For amlodipine and nifedipine it says not to eat grapefruit or drink grapefruit juice because it can increase the chance of side effects. [2][3] For atorvastatin it says to avoid having too much grapefruit juice. [4] For sertraline and warfarin it says not to drink grapefruit juice. [5][6] MedlinePlus tells warfarin users to talk to their doctor about eating grapefruit or drinking grapefruit juice. [7] These are statements about specific medicines in the UK and US, not general rules.

Other citrus

The FDA says Seville oranges (often used for marmalade), pomelos and tangelos (a cross between tangerines and grapefruit) might have the same effect as grapefruit juice, and that fexofenadine may also not work as well with orange or apple juice. [1] For the fruit itself, see Citrus fruits and orange juice.

A note on names: grapefruit is often written Citrus × paradisi Macfad. GBIF lists that name as a synonym of Citrus × aurantium L., so databases differ on the plant's name. [8] The FDA page uses the everyday word "grapefruit."

What a reader can do

• Ask your doctor or pharmacist whether your specific medicine is affected and how much, if any, grapefruit juice is acceptable. [1]
• Read the medication guide or patient information sheet, or the Drug Facts label on over-the-counter drugs. [1]
• If you must avoid grapefruit juice, check the labels of fruit juices and fruit-flavored drinks to see whether they contain it. [1]

Do not start, stop or change a prescribed medicine because of grapefruit; ask the prescriber or pharmacist. Grapefruit essential oil and grapefruit-seed extracts were not covered by the FDA page we read, so we make no statement about them; ask a pharmacist. See also Food and drink interactions with medicines and How interactions work.