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psisci said:
I am not sure where these numbers came from, but in all my pharmacology training, every study that has been reviewed has show miniscule elevations for psych meds with normal grapefruit ingestion.
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Simvastatin:
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=11061578
http://www.ncbi.nlm.nih.gov/entrez/q...t_uids=9834039
The second abstract shows massive inter-individual variability in Cmax increase: mean about 9-fold (range, 5.1-fold to 31.4-fold; P < .01).
Buspirone:
http://www.ncbi.nlm.nih.gov/entrez/q...t_uids=9871430
Again, large variability: "Grapefruit juice increased the mean peak plasma concentration of buspirone 4.3-fold (range, 2-fold to 15.6-fold; P < .01) and the mean area under the plasma buspirone concentration-time curve 9.2-fold (range, 3-fold to 20.4-fold; P < .01)."
Fluvoxamine:
J Clin Psychopharmacol. 2003 Aug;23(4):422-4. (I used a secondary citation of this original, abstract not available)
Sertraline:
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=10890261
Carbamazepine:
http://www.ncbi.nlm.nih.gov/entrez/q...t_uids=9757152
Diazepam (Valium):
http://www.ncbi.nlm.nih.gov/entrez/q...t_uids=9625273
"The mean AUC(0-24) of diazepam was increased 3.2-fold (P < 0.001) and Cmax was increased 1.5-fold (P < 0.05) by the grapefruit juice." ....after a single glass of grapefruit juice (250 mL = approx. 8 oz.).
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I have never met a pharmacologist or psychiatrist who worries about grapefruit.
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That scares me. 50% of all meds are metabolized, at least in part, by 3A4.
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I guess I would only worry about this if someone started a new med that was heavy on 3A4, and the person was just starting a grapefruit diet. The problem with stable kinetics and dynamics studies of any sort is that they are invitro and do not account for the incredible dynamics of a living system.
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I only quoted in vivo (human) work.
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Someone who eats grapefruit for breakfast daily will have upregulated prodiction of the needed enzymes, which will increase clearance of grapefruit and allow for equilibrium if another med or substance needs those enzymes.
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None of the work that I studied showed any evidence of induction of intestinal 3A4 over time. Liver induction is about clearance. This issue is about bioavailability. Luminal 3A4 is the concern.
Lar