Wednesday January 11, 2017 Q&A

Why shouldn’t you eat grapefruit when taking certain medications?


1 the fruit’s acidity dissolves the drug molecules

2 the diuretic effect reduces the drug’s efficacy

3 the drug molecules break down more slowly

Question related image

Correct answer: 3. Grapefruit contains substances that significantly slow the decomposition of the drug molecules. Repeated ingestion of the fruit can increase the levels of the drug in your bloodstream. You may have heard of the effects of grapefruit juice. When prescribing a number of drugs, doctors advise patients to avoid consuming grapefruit and grapefruit juice because certain substances in the fruit could cause undesirable side effects. The main culprits are a group of compounds found in grapefruit called furanocoumarins, especially bergamottin and dihydroxybergamottin. Both substances inhibit the activity of an enzyme that plays a key role in breaking down drugs in the human body. This can lead to higher levels of active molecules in the bloodstream. The problem lies in the prescribed dosage, which takes into account how fast the body breaks down drugs. Given that these substances significantly slow drug metabolism, repeated ingestion of grapefruit can lead to higher levels of the drug in your bloodstream. This can have dangerous consequences. The grapefruit's effects are not exactly fleeting: it takes around 24 hours for the enzyme activity to return to half its initial level and up to 72 hours for it to be completely restored. A whole grapefruit, or 200 milliliters of juice, can interfere significantly with the enzyme’s activity. And the consequences, which depend on the medication taken, go all the way up to kidney damage, blood clots and broken muscle fibers. Pomelos, a hybrid of oranges and grapefruit, demonstrate similar interactions with the enzyme. Tangelos, which are a cross between tangerines and pomelos or grapefruit, only contain trace amounts of bergamottin and do not interact with the enzyme. They can be safely consumed alongside medications that interact with grapefruit. Interestingly, grapefruit’s interaction with medications may have a positive side as well. For example, several molecules used to fight AIDS break down very quickly in the body. Their efficacy could be enhanced if the patient also consumed grapefruit, which would prolong the molecules’ presence in the blood. From the book “Pourquoi l'asperge donne-t-elle une odeur au pipi?” PPUR.