[log in to unmask] wrote:
>
> Thank you, Kathrynne.
> Your reply clears the question nicely.
> [log in to unmask]
> ---------------------
> Forwarded message:
> From: [log in to unmask] (Kathrynne Holden, MS,RD)
> To: [log in to unmask]
> Date: 97-07-04 06:12:51 EDT
>
> [log in to unmask] wrote:
> > with medications I quoted from The Medical Letter VOL. 37(Issue 955)
> > Aug.15,1995:
> > "CONCLUSION - Grapefruit juice inhibits presystemic metabolism of >some
> drugs metabolized by the cytochrome P450 isozme CYP3A4, including >several
> calcium channel blockers, cyclosporine and terfendine. With >drugs like
> these which are largely metabolizrd presystemically, >grapefruit juice may
> increase serum concentrations by allowing more >unmetabolized drug to enter
> the systemic > circulation.
>
> Hi Mary -- yes, a degree in pharmacology would be helpful, wouldn't it?
>
> "Metabolism" means the processes our body goes through to break down,
> use, and excrete food. "Presystemic metabolism" means the metabolic
> processes that take place before the food enters the bloodstream.
> Metabolism begins with chewing and adding saliva to food, continues in
> the stomach and intestine. From there, the broken-down food particles
> either go into the bloodstream for distribution, or continue into the
> colon for excretion.
>
> The drugs in question are supposed to be metabolized before they get to
> the bloodstream, but the grapefruit juice inhibits this. So
> un-broken-down drug particles go into the bloodstream, or "system." This
> could increase the drug's effect.
>
> > Then Ted inquired:
> > >I love grapefruit juice
> > > Can you tell me what those Refs.said?
>
> Unless you're taking any of those drugs, you probably don't have
> anything to worry about. But to be on the safe side, go to a friendly
> pharmacist, give him/her your list of medications, say you love you
> daily grapefruit juice, and ask if it could cause any problems for you.
>
> Best regards,
> Kathrynne
> --
> Kathrynne Holden, MS, RD
> Editor-in-Chief,
> "Spotlight on Food--nutrition news for people 60-plus"
> http://www.fortnet.org/~fivstar
> and NUTRITION TOPICS copy-ready handouts
> http://www.dietetics.com/class/fivstar/
> Tel: 970-493-6532 Fax: 970-493-6538
To all interested parties:
Just to add a bit of explanation. The cytochrome P450 isozyme refers to
a liver enzyme system. The liver enzymes in this system are responsible
for breaking down (metabolizing) the drugs in question. The grapefruit
juice inhibits the production of these enzymes, so consequently the
drugs are not metabolized as fast and stay in the blood stream longer
and in a higher concentration. Is this as clear as mud?
Jerry Starr RPh.
