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Dear all,
Is there any information about a possible interaction
between phenytoin antiepileptic drug and ascorbic acid
(vitamin c).
If yes, what is the suggested mechanism?. please
mention any reference.
Best regards,
Dr. Ehab EL Desoky
Assistant professor of pharmacology
Faculty of Medicine
Assiut University
Assiut. Egypt
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Dear Ehab
here is abstract of one of the paper related to Phenytoin vs Vitamin c
Effects of phenytoin, phenobarbital, and ascorbic acid on misonidazole
elimination.
WilliamsK, BeggE, WadeD, O'SheaK
Clin Pharmacol Ther 1983Mar 33:314-21
The kinetics of an oral dose (1.0 gm/m2) of the 2-nitroimidazole
radiosensitizer misonidazole were studied in three groups of six
healthy subjects before and after a 1-wk course of phenytoin,
phenobarbital, or ascorbic acid. Phenytoin and phenobarbital decreased
mean misonidazole half-life by 27% and 23% and the decrease was
associated with the respective increases in mean clearance of 42% and
31%. The area under the plasma concentration-time curve for the
metabolite O-desmethylmisonidazole increased correspondingly. Volume of
distribution of misonidazole was unchanged. After treatment with
ascorbic acid there was a very small increase in the mean clearance of
misonidazole, but there was no significant change in other kinetic
parameters. Induction by phenytoin and phenobarbital of the oxidative
metabolism of misonidazole is the most likely mechanism responsible.
Deliberate induction of a patient's metabolism may help to reduce the
neurotoxicity associated with the use of the drug. The efficacy of the
radiosensitizing action of the drug is unlikely to be compromised under
these conditions since peak plasma concentrations of misonidazole were
not affected by treatment with either phenytoin or phenobarbital. The
potentiation of the cytotoxic effects of misonidazole by ascorbic acid
is unlikely to be related to a direct effect on the oxidative
metabolism of misonidazole.
---
I think this reference will help you
Ascorbic acid concentrations in human plasma and cerebrospinal fluid
[proceedings].
RidgeBD, FairhurstE, ChadwickD, ReynoldsEH
Proc Nutr Soc 1976Sep 35:57A-58A
All the best
Dr M Habibuddin
Assist. Prof. of Pharmacy
CHS
ABHA
KSA
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