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Eur J Clin Pharmacol. 2003 Apr;58(12):829-33. Epub 2003 Mar 15.

Effects of concomitant fluvoxamine on the metabolism of alprazolam in Japanese psychiatric patients: interaction with CYP2C19 mutated alleles.

Author information

1
Department of Psychiatry, Niigata University Graduate School of Medical and Dental Science, 1-757 Asahimachi, 951-8510, Niigata, Japan.

Abstract

OBJECTIVES:

Administration of fluvoxamine (FLV) with concomitant benzodiazepines is common in clinical situations. We studied the effects of the coadministration of FLV on plasma concentrations of alprazolam (ALP). We also studied the effects of CYP2C19(*)2 or CYP2C19(*)3 on these drug interactions.

METHODS:

The subjects were 23 Japanese outpatients all concomitantly treated with FLV either before or after monotherapy with ALP. We measured the plasma concentrations of ALP and FLV using a column-switching, high-performance liquid chromatographic method with ultraviolet detection. The CYP2C19(*)2 or CYP2C19(*)3 alleles were identified using a polymerase chain reaction analysis.

RESULTS:

Coadministration with FLV produced significant, on average 58%, increases in the plasma concentrations of ALP ( P<0.001). There were, however, wide variations in the interactive effects of the coadministration of FLV on the plasma concentrations of ALP. While there were some subjects who had greater increases in plasma ALP concentrations, more than 100%, in response to the coadministration of FLV among the subjects with no mutated or one mutated allele, there are no subjects who had increases in plasma ALP concentrations of more than 50% among the subjects with two mutated alleles. The differences of these variances among the three genotype groups reached a level of significance ( P<0.05).

CONCLUSION:

Coadministration of FLV significantly increased the plasma concentrations of ALP compared with ALP monotherapy. Wide variations were observed in the drug interactions, with the CYP2C19 genotype possibly being related to these interactions.

PMID:
12698310
DOI:
10.1007/s00228-003-0563-9
[Indexed for MEDLINE]

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