Grapefruit interacts with more than 85 drugs, including buspirone, quetiapine, lurasidone, ziprasidone and pimozide
One whole grapefruit or 200 mL of juice is enough. The effect on the gut enzyme CYP3A4 is irreversible, so it lasts: 50 percent of maximum at 10 hours, 25 percent at 24. Older people are "an especially vulnerable population."
Weak or heavily disputed. Treat as a question, not an answer. how we score evidence
Caveat on this rating: A narrative review; "known or predicted to interact" includes predictions from pharmacology, not only documented cases. Most of the serious harms tabulated are for cardiovascular and transplant drugs, not psychiatric ones.
The one interaction in this wave that comes from the breakfast table.
Significant findings
Bailey, Dresser and Arnold (CMAJ, 2013) reviewed the grapefruit literature. "Currently, more than 85 drugs ... are known or predicted to interact with grapefruit," and between 2008 and 2012 the number with the potential for serious adverse effects rose "from 17 to 43."
The mechanism is furanocoumarins in the fruit causing "irreversible inactivation" of the enzyme CYP3A4 in the small intestine, so that drugs normally broken down there reach the blood in larger amounts. Because the enzyme is destroyed rather than blocked, the effect outlasts the fruit: a dose taken within 4 hours of grapefruit shows the maximal interaction, at 10 hours the effect is "50% of the maximum," at 24 hours "25% of the maximum." "One whole grapefruit or 200 mL of grapefruit juice is sufficient" to produce a clinically relevant effect.
On who is affected: "Older people appear to be an especially vulnerable population for grapefruit-drug interactions," with pronounced effects in patients over 70.
The psychiatric and neurological drugs in the review's tables include buspirone, quetiapine, lurasidone, ziprasidone, pimozide, dextromethorphan, oral ketamine, oxycodone, oral fentanyl and triazolam.
Worth asking
Most of the drugs on the list are raised, not lowered, which for an antipsychotic means more sedation and, for pimozide and ziprasidone, more QT prolongation. The pharmacist's answer to "can I drink grapefruit juice" depends entirely on which drugs you take, and the review's 24-hour figure means "not at the same time as the pill" is not the same as "not at all." Seville oranges, used in marmalade, contain the same compounds.
Source
Grapefruit-medication interactions: forbidden fruit or avoidable consequences? — Bailey DG, Dresser G, Arnold JM (2013)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1503/cmaj.120951
DOI: 10.1503/cmaj.120951
How this was scored
- Study design
- Narrative review
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published September 21, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "contested". Weak or heavily disputed. Treat as a question, not an answer. It scores 33 out of 100 on our published rubric. One caveat travels with that badge: A narrative review; "known or predicted to interact" includes predictions from pharmacology, not only documented cases. Most of the serious harms tabulated are for cardiovascular and transplant drugs, not psychiatric ones. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Grapefruit-medication interactions: forbidden fruit or avoidable consequences? — Bailey DG, Dresser G, Arnold JM (2013). Published in: Reputable peer-reviewed journal. DOI: 10.1503/cmaj.120951. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Narrative review. Funding: Funding not disclosed. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.