PHARMACOKINETICS AND DISPOSITION CYP2C9 genotypes and diclofenac metabolism in Spanish healthy volunteers Received: 18 November 2002 / Accepted: 12 February 2003 / Published online: 7 May 2003 Ó Springer-Verlag 2003 Abstract Objective: This study analyzed the frequency of CYP2C9 variant alleles and evaluated the impact of CYP2C9 genotype on diclofenac metabolism in a Spanish population. Methods: Diclofenac hydroxylation capacity was studied in a population of 102 healthy volunteers. After a single oral dose of 50 mg diclofenac the 0- to 8-h urinary concentrations of diclofenac and its main metabolites, 4’-hydroxy (OH), 3¢-OH and 5-OH diclofenac were analyzed by high-performance liquid chromatography. CYP2C9 genotyping for the variant alleles CYP2C9*2 and *3 was carried out with PCR-RFLP. Results: The frequencies of CYP2C9*1, *2, and *3 al- leles were 0.74 (95%CI: 0.68–0.80), 0.16 (95%CI: 0.11– 0.21) and 0.10 (95%CI: 0.06–0.15), respectively, among the 102 Spaniards studied. The diclofenac/4’-OH dic- lofenac urinary ratio, but not the diclofenac/3¢-OH dic- lofenac and diclofenac/5-OH diclofenac ratios, was related to CYP2C9 genotype. The diclofenac/4’-OH ra- tio was significantly higher among subjects with CYP2C9*1/*3 (0.83±0.4, n=14, 95% CI for the dif- ference: 0.02–0.4) and CYP2C9*2/*3 (1.10±0.5, n=4, 95% CI for the difference: 0.16–0.8) genotypes com- pared to CYP2C9*1/*1 (0.62±0.3, n=59) and approx- imately threefold higher (1.8) in the only subject homozygous for CYP2C9*3 variant. Conclusions: The frequencies of CYP2C9*1, *2, and *3 alleles in the Spanish population reported here were similar to those found in the previously studied white European populations, and different of the previously reported in another Spanish population. CYP2C9*3 allele seems to influence the 4’-hydroxylation of dic- lofenac, although there is a large overlapping in the urinary metabolic ratio between the genotype groups studied. Keywords Diclofenac Æ CYP2C9 Æ Genotyping Introduction The polymorphic CYP2C9 has been reported to catalyze the metabolism of many clinically important drugs such as phenytoin, S-warfarin, tolbutamide, losartan, and several nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac [1, 2, 3, 4, 5, 6]. Several allelic variants of the CYP2C9 gene causing decreased enzyme activity have been identified. CYP2C9*2 has a point mutation in exon 3 which is responsible for the amino acid change Arg 144 Cys, CYP2C9*3 has an exon 7 point mutation causing Ile 359 Leu change and CYP2C9*4 has an exon 7 mutation causing Ile 359 Thr change [4, 7, 8, 9, 10, 11]. A number of other variant alleles have also been identified but their functional significance remains to be established (Nomenclature Committee, www.imm.ki.se/ CYPalleles). Many studies have shown interethnic dif- ferences in the frequencies of CYP2C9 alleles [2, 8, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]. So far only one study analyzed the CYP2C9 genotype among Spaniards Eur J Clin Pharmacol (2003) 59: 221–225 DOI 10.1007/s00228-003-0588-0 Pedro Dorado Æ Roland Berecz Æ Maria-Jesu´ s Norberto U ¨ mit Yasar Æ Marja-Liisa Dahl Æ Adria´n LLerena P. Dorado Æ R. Berecz Æ M.-J. Norberto Æ A. LLerena (&) Department of Pharmacology and Psychiatry, Faculty of Medicine, University of Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain E-mail: allerena@unex.es Tel.: +34-924-289467 Fax: +34-924-289467 U ¨ . Yasar Department of Clinical Pharmacology, Huddinge University Hospital, Karolinska Institute, Stockholm, Sweden M.-L. Dahl Department of Medical Sciences, Clinical Pharmacology, University Hospital, Uppsala, Sweden A. LLerena University of Beira Interior, Covilha˜, Portugal Present address: R. Berecz Department of Psychiatry, Medical and Health Science Centre, University of Debrecen, Debrecen, Hungary