Grapefruit interactions

[Paracelsus]

It is pretty well known that grapefruit potentiates many drugs, including opiates, caffeine, benzos and DXM. It does this by inhibiting several cytochrome P450 enzymes (CYP3A4, CYP1A2), which affects the metabolism of the drug.

There is many info around on potentiating various substances with grapefruit, but no 'central' grapefruit thread.

Please post here what you can find about pharmacological activity of grapefruit and interactions with recreational drugs and other substances. How much grapefruit juice is drunk, what drugs does it potentiate/modify effects, what is the degree of potentiation, what drugs grapefruit does NOT affect, what other interactions exist (there are some substances dangerous to combine with grapefruit juice).

Some internal resources:
Grapefruit Juice And Benzodiazepines: http://www.drugs-forum.com/forum/showthread.php?t=26819
Various methods of potentiating opiates: http://www.drugs-forum.com/forum/showthread.php?t=10884
Grapefruit and methadone: http://www.drugs-forum.com/forum/showthread.php?t=28298
File archive is useful too.

What I know:

GFJ (grapefruit juice) potentiates DXM, by not letting it be cleaved into DXO. It also modifies the experience (read the DXM FAQ and the Grapefruit Juice FAQ on third-plateau).

GFJ potentiates benzodiazepines.There's a link above. There are also some papers in the file archive about this.

GFJ potentiates caffeine (not sure, SWIM didn't confirm this, as the effects of caffeine are hardly noticeable to him) and makes it last longer.

GFJ potentiates many opiates. Except those that have to be N-demethylated to be active (tilidine)

Terfenadine (Seldane) and GFJ is a dangerous combination (I've read somewhere about deaths), because terfenadine needs CYP3A4 to be metabolized into the active metabolite fezofenadine, while terfenadine itself is cardiotoxic (http://en.wikipedia.org/wiki/Seldane).

Anything else? Maybe more data about to what degree (%) is the drug potentiated, etc.

Reputation Comments on this post:

good start-up thread