Grapefruit and medications

Written by Catherine Saxelby on Tuesday, 10 March 2009.
Tagged: food safety, fresh food, special diets, tips

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Grapefruit and grapefruit juice can interact with a number of medications, either making them work too strongly or causing unpleasant side effects. The juice is generally singled out over the fruit because it's concentrated and easy to consume a lot of grapefruit - one small 200 mL glass is the equivalent of 2 or 3 grapefruit.

Grapefruit inhibits two key enzymes in the inner lining of the intestine (called cytochrome P450 enzyme and P-glycoprotein).

These enzymes usually slow the absorption of the drugs into the body. Once they are ‘inactivated', there's nothing to prevent the drug getting in so you get an increase in the amount of parent drug available for absorption. This may result in an ‘exaggeration' in its effect with these symptoms.

For the calcium-channel blockers, it's usually low blood pressure (hypotension) and related symptoms such as feeling dizzy or weak.
For the statins, it's usually muscle weakness (myalgia) and associated effects.

Check what medication you take

The list of drugs that get enhanced by grapefruit juice are:

some heart and blood pressure medicines eg, amiodarone (Cordarone X) and felodipine (Felodur, Plendil)
many of the cholesterol-lowering medicines known as statins particularly atorvastatin (Lipitor) or simvastatin (Lipitor, Lipex, Zimstat, Mevacor, Zocor, other brands) as well as cyclosporin, saquinavir and cisapride.
some drugs that suppress the immune system
minor tranquillisers (benzodiazepines) such as midazolam and triazolam
anti-anxiety drugs

Grapefruit juice doesn't increase the effect of pravastatin (Pravachol), however, because it is metabolized differently.

Latest advice

Avoid grapefruit and grapefruit juice all together
Or
Have grapefruit each and every day
(tell your doctor and ask him/her to adjust the dose if necessary)

You can't take your medication and the grapefruit juice separately. There's evidence it can last 24 hours or longer, though it trails off. Moreover the effect can vary from person to person and even from grapefruit to grapefruit.

I love grapefruit and am always amazed at how it can interfere with these medicines. Such a shame as it's grapefruit are very high in vitamins, minerals and fibre and make a top inclusion at breakfast. Read here why grapefruit is one of my superfoods.

This information was sourced directly from the Adverse Drug Reactions section of the Therapeutic Goods Administration.

If you have any questions regarding grapefruit juice and medications, seek advice from your health care provider.