Should You Drink Grapefruit Juice with Fluoroquinolone Drugs? - Fluoroquinolone Toxicity Research

Should You Drink Grapefruit Juice with Fluoroquinolone Drugs?

Should you drink grapefruit juice with Fluoroquinolone drugs such as Levaquin, Cipro, and Avelox? In fact, many people who have been ‘floxxed’, another name for having been damaged by these drugs, may have been drinking grapefruit juice when they took these drugs. Perhaps they don’t even remember if they did or not. However, drinking grapefruit juice when taking these drugs could have precipitated the serious damage they incurred.



grapefruit juice fluoroquinolones cipro and levaquin

For starters, if you are unfamiliar with the serious damage these drugs can cause, I invite you to read our Introduction to Fluoroquinolone Toxicity  to learn more about the serious problems these drugs can cause and why you should stay away from them. Also see our List of Fluoroquinolones to know if the drug you are taking is in the fluoroquinolone class. Then keep reading to find out why taking them with grapefruit juice is an even worse idea than taking the drugs by themselves and how you could be inviting big problems into your life.

How We Know Grapefruit Juice Is a Problem

While grapefruit juice is delicious who could have imagined that this typical morning drink can be a real problem when it comes to taking medications? Well, no one really did know until about 30 years ago when they were doing a study to see if drinking alcohol would be a problem when someone was taking blood pressure medications. In studies, they do a procedure called a ‘double blind placebo controlled study’ where no one knows if they are taking the study substance or not.

Since it’s pretty difficult to cover up the taste of alcohol so that people don’t know which arm of the study they are in, they tried to cover it up using grapefruit juice. However, people began having serious problems with their blood pressure and the they traced it to the grapefruit juice! Since then, there have been thousands of studies done on grapefruit juice, and it was found that there are significant drug interactions with many different drugs.


Stephen Fried is an investigative journalist who turned his attention to the dangers of prescription drugs when his wife nearly died from taking the quinolone antibiotic Floxin. Bitter Pills, the book below, is the result of his extensive research on these drugs.


After many hundreds of tests, it was found that a group of chemicals in grapefruit juice, the furanocoumarins, and not the naringinens as previously believed, inhibit something called the cytochrome P450 isoenzyme system (1), and specifically the CYP3A enzyme within the cytochrome P450 isoenzyme system. This is a group of enzymes that detoxify substances in the liver. A large number of medications are detoxified by this system, and that is a problem because it can cause medications not to be detoxified properly.

What this means, for most medications, is that they will stay in the system much longer than they would otherwise while some, like epileptic drugs, can be detoxified more quickly, which could allow people taking them to have more seizures. There’s a more comprehensive page on Grapefruit Juice Side Effects here. So, is grapefruit juice with fluoroquinolone drugs a problem?


Fluroquinolone Drugs and the Cytochrome P450 Enzyme System

The Fluoroquinolone drugs are also inhibitors of the cytochrome P450 enzyme system, however, most of the drugs in the class, while inhibiting the P450 enzyme system, inhibit different subenzymes within the system than are effected by grapefruit juice.

Ciprofloxacin showed weak inhibition on both the activity of CYP1A2 (IC50 135 micromol/L) and CYP2C9, levofloxacin inhibited only CYP2C9, and Caderofloxacin, antofloxacin, moxifloxacin, and gatifloxacin showed weak inhibition of the CYP1A2 or CYP2C9 enzymes (3) and therefore Levofloxacin Toxicity was not worsened. A very thorough search of the literature could find no warnings and no case studies of anyone claiming to have been negatively affected specifically from the combination of the fluoroquinolone drugs along with grapefruit juice.

grapefruit interactions cipro levaquin fluoroquinolone drugs

While we would still advise caution on the matter and advise that no one drink grapefruit juice while taking these drugs, due to the fact that there are so many other Grapefruit Juice Drug Interactions, but it would seem, based on a very thorough search and many years of listening to thousands of people who have been negatively affected by the fluoroquinolone drugs, that grapefruit juice is most likely not a problem when taking these drugs, and is most likely not a contributing factor in the development of fluoroquinolone toxicity.

If you had a different experience and feel that grapefruit juice was definitely a problem for you while taking the fluoroquinolone class of drugs, we’d love to hear your story below. Do watch out for other Fluoroquinolone Drug Interactions, such as the Dangerous Interaction with Iron, it’s Interactions with Common Painkillers and Levaquin and Prednisone Interactions.

Resources for this article

1. Effect of Ciprofloxacin and Grapefruit juice on oral pharmacokinetics of Riluzole in Wistar rats
2. Drug Interactions with Grapefruit Juice
3. Determination of the Inhibitory potential of 6 fluoroquinolones on CYP1A2 and CYP2C9 in human liver microsomes


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