Grapefruit and medication intake: be careful!

Grapefruit is known to be an interesting source of vitamin C. Studies have also shown its benefits on diabetes and cardiovascular problems. However, be careful when eating grapefruit if you're taking medication. Here’s why…

Even though it has 𝐚𝐧𝐭𝐢𝐨𝐱𝐢𝐝𝐚𝐧𝐭 𝐚𝐧𝐝 𝐚𝐧𝐭𝐢-𝐢𝐧𝐟𝐥𝐚𝐦𝐦𝐚𝐭𝐨𝐫𝐲 𝐩𝐫𝐨𝐩𝐞𝐫𝐭𝐢𝐞𝐬 due to its composition, grapefruit is known to be involved in 𝐧𝐮𝐦𝐞𝐫𝐨𝐮𝐬 𝐝𝐫𝐮𝐠 𝐢𝐧𝐭𝐞𝐫𝐚𝐜𝐭𝐢𝐨𝐧𝐬. A study published in 2013 listed 58 oral medications that interacted with grapefruit, 43 of which may cause 𝐬𝐞𝐫𝐢𝐨𝐮𝐬 𝐜𝐨𝐦𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬. But what is the mechanism behind these interactions?

This phenomenon is due to the 𝐢𝐧𝐡𝐢𝐛𝐢𝐭𝐢𝐨𝐧 𝐨𝐟 𝐝𝐫𝐮𝐠-𝐦𝐞𝐭𝐚𝐛𝐨𝐥𝐢𝐳𝐢𝐧𝐠 𝐞𝐧𝐳𝐲𝐦𝐞𝐬 in the intestine and liver, mainly the CYP3A4 enzyme (cytochrome P450), by furanocoumarins. When these 𝐞𝐧𝐳𝐲𝐦𝐞𝐬 𝐚𝐫𝐞 𝐢𝐧𝐡𝐢𝐛𝐢𝐭𝐞𝐝 𝐢𝐧 𝐭𝐡𝐞 𝐢𝐧𝐭𝐞𝐬𝐭𝐢𝐧𝐞, drug metabolism is reduced and the amount of unmetabolized drug entering the bloodstream is 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐝, 𝐩𝐨𝐭𝐞𝐧𝐭𝐢𝐚𝐥𝐥𝐲 𝐥𝐞𝐚𝐝𝐢𝐧𝐠 𝐭𝐨 𝐨𝐯𝐞𝐫𝐝𝐨𝐬𝐞. In rarer cases, grapefruit ingestion may cause 𝐚 𝐝𝐞𝐜𝐫𝐞𝐚𝐬𝐞 𝐢𝐧 𝐭𝐡𝐞 𝐚𝐦𝐨𝐮𝐧𝐭 𝐨𝐟 𝐝𝐫𝐮𝐠 𝐢𝐧 𝐭𝐡𝐞 𝐛𝐥𝐨𝐨𝐝, probably due to a reduced absorption in the intestine. In addition, studies have shown that grapefruit juice has an impact on drug metabolism if taken 𝐝𝐮𝐫𝐢𝐧𝐠 𝐦𝐞𝐝𝐢𝐜𝐚𝐭𝐢𝐨𝐧 𝐢𝐧𝐠𝐞𝐬𝐭𝐢𝐨𝐧 or 𝐰𝐢𝐭𝐡𝐢𝐧 𝟒 𝐡𝐨𝐮𝐫𝐬 𝐛𝐞𝐟𝐨𝐫𝐞 𝐭𝐫𝐞𝐚𝐭𝐦𝐞𝐧𝐭.

In short: if you're a grapefruit juice lover and you're taking an oral medication, 𝐜𝐚𝐫𝐞𝐟𝐮𝐥𝐥𝐲 𝐫𝐞𝐚𝐝 𝐢𝐭𝐬 𝐢𝐧𝐬𝐭𝐫𝐮𝐜𝐭𝐢𝐨𝐧𝐬, 𝐨𝐫 𝐚𝐬𝐤 𝐲𝐨𝐮𝐫 𝐩𝐡𝐚𝐫𝐦𝐚𝐜𝐢𝐬𝐭.
Moreover, although grapefruit has been studied the most, similar effects on certain drugs have been reported with other citrus fruits, such as oranges and lemons.