Talk:Grapefruit
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Grapefruit juice enhances the effect of some commonly used medications by increasing their bioavailability or half life via the selective down-regulation of a specific subfamily of the cytochrome P450 enzyme system in the small intestine- most notably CYP3A4. This effect can be seen with a single grapefruit or 200mL of grapefruit juice, and persist for as much as 3 days.
Grapefruit-drug interactions typically cause increased amounts of the drug in the body, however in a few cases it can cause a decrease.
A number of recreational drugs are affected by grapefruit. Notable examples include:
- Most benzodiazepines - although the effect may be very minor depending on the specific drug.
- Ketamine - when used intranasally or orally, but not when used IM or IV, has increased absorption and duration from grapefruit.
- Oxycodone - which can have the half life increased by 50%
- Methadone - but only to a very small extent.
- Codeine - is metabolised into inactive norcodeine by CYP3A4. Grapefruit inhibits CYP3A4, so more morphine is produced, which might be dangerous
- Buprenorphine - but the extent of the effect is unknown.
- Other opioids - may also be affected but more research is needed.
- Erectile dysfunction drugs Viagra, Cialis and Levitra show somewhat increased blood levels.
- Cocaine - serum levels may be increased, but has not been well studied.
- DXM - is metabolised into inactive 3-MM by CYP3A4. Grapefruit inhibits CYP3A4, so more DXO is produced, which is also metabolised by CYP3A4.
If one chooses to combine grapefruit with recreational drugs, it may also affect non-recreational drugs, including:
- Estradiol - Grapefruit and grapefruit juice decrease the breakdown of estrogen in the body
- Fexofenadine - Fexofenadine is transported into the body by OATP1A2, which is inhibited by grapefruit