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Grapefruit Juice, CYP3A4 and Supplement Interactions

Question:
I've heard that grapefruit juice can interact with medications because it inhibits an enzyme that breaks down drugs in the body. Do any supplements interact the same way with drugs?
Grapefruit Juice, CYP3A4 and Supplement Interactions -- Grapefruit half and supplements pills
Answer:
Yes, it's well-known that grapefruit juice can interact with many medications, including certain cholesterol-lowering statin drugs, blood pressure drugs, antihistamines, and sedatives. One of the ways grapefruit does this is by inhibiting CYP3A4, an enzyme in the liver and intestine that helps metabolize (break down) approximately 50% of all medications. This can lead to potentially excessive blood levels of these medications, increasing their effects and side effects. 

Many supplements can also inhibit (and in some cases, activate) CYP3A4 and interact with many of the same medications. 

Below is a list of some of the supplements known to inhibit CYP3A4. More details about each are found in our linked Product Reviews and CL Answers:   Be aware that St. John's wort can activate CYP3A4, causing a decrease in the activity of many drugs.

To see a list of medications that are metabolized by CYP3A4, sign in >>

Learn more about supplement and drug interactions:



I take omeprazole (Prilosec), a proton pump inhibitor, to reduce stomach acid. Are there supplements I should avoid, or be taking, due to this drug? >>

When taking a statin drug like Lipitor or Crestor, are there supplements I should avoid or take? >>

I take levothyroxine (Synthroid), a thyroid hormone to treat hypothyroidism. Are there supplements I should avoid, or be taking, due to this drug? >>

I take lisinopril (Zestril), an ACE inhibitor drug to lower blood pressure. Are there supplements I should avoid, or be taking, due to this drug? >>

I take warfarin (Coumadin), an anticoagulant drug. Are there supplements I should avoid, or be taking, due to this drug? >>

Are there any supplements I should avoid when taking aspirin or ibuprofen? >>

See other recent and popular questions >>
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This CL Answer initially posted on 2/12/2019.
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