“Grapefruit juice can cause less fexofenadine to enter the blood,” decreasing how well the drug works, Huang says. Fexofenadine (brand name Allegra) is available as both prescription and OTC to relieve symptoms of seasonal allergies. Fexofenadine may also not work as well if taken with orange or apple juice, so the drug label says, “Do not take with fruit juices.”
When drugs are swallowed, they may be broken down (metabolized) by enzymes and/or absorbed using transporters in cells found in the small intestine. Grapefruit juice can cause problems with these enzymes and transporters, causing too much or too little drug in the body.
Some drugs, like certain statins used to lower cholesterol, are broken down by enzymes. As shown above, grapefruit juice can block the action of these enzymes, increasing the amount of drug in the body and may cause more side effects.
Grapefruit juice and grapefruit can be part of a healthy diet. Grapefruit has vitamin C and potassium, nutrients your body needs to work properly.
How Grapefruit Juice Can Interfere With Medications
For example, if you drink a lot of grapefruit juice while taking certain statin drugs to lower cholesterol, too much of the drug may stay in your body, increasing your risk for liver and muscle damage that can lead to kidney failure.
Here are examples of some types of drugs that grapefruit juice can cause problems (interact) with:
With most drugs that are affected by grapefruit juice, “the juice lets more of the drug enter the blood,” says Shiew Mei Huang, Ph.D., of the FDA. “When there is too much drug in the blood, you may have more side effects.”
How Grapefruit Juice Affects Some Drugs
The amount of the CYP3A4 enzyme in the intestine varies from person to person. Some people have a lot of this enzyme and others just a little. So grapefruit juice may affect people differently even when they take the same drug.
Grapefruit juice does not affect all the drugs in the categories above. The severity of the interaction can be different depending on the person, the drug, and the amount of grapefruit juice you drink. Talk to your health care provider or pharmacist, and read any information provided with your prescription or non-prescription (OTC) drug to find out:
A low dose of a med could become a high dose if it’s not properly broken down and eliminated. A high dose of a med could become a dangerously high dose, or even an overdose. Drugs with a narrow “therapeutic window” (they must stay within a certain blood-concentration range) are especially susceptible.
What’s the best path forward?
At a minimum, the evidence at this point suggests that grapefruit warnings on medications should also apply to CBD. And it’s important to check with your doctor before taking CBD, especially if you’re taking other medications.
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Interest in cannabidiol (CBD) is exploding. Now that major retailers are carrying CBD products, plus an enormous selection online, curiosity is only going up. But we also need some healthy skepticism and caution to balance out the exuberance. CBD research is still in the early stages, and marketing is predictably outpacing facts. Concerns about safety, among other topics, are getting lost in the hype.
CBD is similar to grapefruit in that it also binds with those enzymes, but research suggests that it’s possibly even more potent because it binds in multiple parts of the gut and liver (grapefruit mainly affects enzymes within the small intestine). Once an enzyme has been inhibited, the effect isn’t immediately reversed. It can take days for enzyme function to return to baseline and start the process again.
What CBD and grapefruit have in common
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The reason for the warning is that grapefruit contains compounds called furanocoumarins that bind with and effectively neutralize enzymes in the gut (specifically a type called CYP450 enzymes), which help break down and eliminate drugs from the body. When these enzymes can’t do their job, too much of the drug enters the liver and flows unprocessed into the bloodstream. That elevates risk of having dangerously high levels of the drug in your system.
What’s the risk?
You’re ready to try CBD. You’ve hit the point where you’re curious enough, or desperate enough, or educated enough to try it.
The Grapefruit Warning
CBD, like grapefruit, interacts with certain medications in a way that can be dangerous. Forbes explains this effect well:
When should I avoid CBD?
There’s just one thing you need to know before you dive in: