Grapefruit Could Cause You to Overdose on Prescription Drugs

Illustration for article titled Grapefruit Could Cause You to Overdose on Prescription Drugs

I always thought the saying that grapefruit was as bitter as death was just a metaphor. Turns out, it's a warning. If you're on medication, grapefruit can be surprisingly dangerous. It can force your body to overdose.


In 1998, a group of researchers decided to do a study on the interaction between felodipine, a drug prescribed for high blood pressure, and ethanol. They believed that "a non-intoxicating amount" of ethanol increased felodipine's effectiveness. Ethanol's more common name is booze, and as it is unsafe and unpleasant to distill it too much, the researchers in charge of the study cast about for a way to mask its taste. They decided to use grapefruit juice, trusting that study participants wouldn't be able to pick out a little liquor in eight ounces of pure bitterness.

After reviewing the results, the researchers were puzzled. They had controlled the amount of drug that the participants ingested, and yet it was present in the participant's blood at levels five times higher than they had expected. As this happened whether there was alcohol in the juice or not, they ruled out the alcohol as the culprit. After also ruling out simple lab mix-ups, they were left with only one conclusion. Grapefruit juice had flooded the participants' systems with drugs.

Today, there is a list of 85 different drugs that interact dramatically with grapefruit or grapefruit juice. Most of the time, the juice causes overdoses. The body, unsurprisingly, isn't keen on accepting whatever drugs happen to make it into the gut. There is an army of systems designed to break down anything a person happens to ingest to its most basic (and harmless) components. Among this army is cytochrome P450 3A4, or CYP3A4. It's an enzyme that rips drugs apart. Correct dosages for these drugs are calculated with this enzyme in mind. Through experimentation, researchers are able to estimate how much of a drug gets broken down, and send in a large enough dose so that some of it gets absorbed into a person's system. Grapefruit juice blocks the enzyme. With the enzyme out of the way, the entire dose of the drug invades. People can overdose just by drinking a glass of juice for breakfast.

They can also under-dose, as well. Grapefruit juice, on its rampage through the body, also takes out a group of transporters in the metabolism. When these transporters are inactivated, they stop transporting certain drugs into the bloodstream. Everyone has different amounts of enzymes and transporters in their body, which is why most medication doses need to be fine-tuned over a period of time. It also means that, depending on the circumstances, grapefruit juice can dose a person with five times their expected amount of medication, or completely block the medication from their system.

Grapefruit is not alone in this behavior. Other citrus fruits, like oranges and limes, have the same effect, but to a far lesser degree. Grapefruit just happens to be the worst, and most disgusting-tasting, culprit of the citrus family.

[Via Grapefruit Juice Drug Interactions, Grapefruit Juice and Drugs May Not Mix, Grapefruit-Medication Interactions.]




Yup, it's amazing how few doctors will warn you about it too... By the time a doctor mentioned I should avoid it because they'd put me on a new med it amplified the uptake of significantly it had been about 10 years since I'd started taking meds it interacted with and I was on at least 3 others at that point :/

Good thing I loathe grapefruit...I used too down Benzo's like candy and I had pushed my luck a bit at times with that...If I had thrown in something like that to even double my absorption it could have easily become life threatening...Although to be fair I wasn't exactly too concerned with such things at the time as one tends not too be when alternating between Benzo's and shots of tequila >_<..But still I knew the odds I was playing with, once you throw in an unknown factor things quickly go downhill.

One thing too note is psychiatric meds are particularly bad for it...If you look through the lists of medications grapefruit interacts with it covers anti-depressants, mood stabilizers, sedatives and stimulants plus others...basically if you've been prescribed anything for mental health of any form just avoid the damn stuff :P

*edited to fix partial sentence*