ArticleEuropean journal of clinical pharmacology2009
Phenotyping of N-acetyltransferase type 2 and xanthine oxidase with caffeine: when should urine samples be collected?
Article in European journal of clinical pharmacology, 2009. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
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Who cites it
6 citing papers in PubMed.
- Article
- Determination of Urinary Caffeine Metabolites as Biomarkers for Drug Metabolic Enzyme Activities.Nutrients · 2019Article
- Genetic variation in aryl N-acetyltransferase results in significant differences in the pharmacokinetic and safety profiles of amifampridine (3,4-diaminopyridine) phosphate.Pharmacology research & perspectives · 2015Article
- Article
- Improved genotyping of N-acetyltransferase 2: role of the ultra-slow acetylators.EXCLI journal · 2013Article
- In vivo evaluation of CYP2A6 and xanthine oxidase enzyme activities in the Serbian population.European journal of clinical pharmacology · 2010Article
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Authors and funding
6 authors.
Funding
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Abstract
objectivesIndividual activities of N-acetyltransferase 2 (NAT2) and of xanthine oxidase (XO) can be assessed using ratios of urinary caffeine metabolites. We investigated how ratios changed over time and which urine collection interval would be the best for NAT2 and XO activity assessments.
methodsOn two occasions separated by 14 days, 16 healthy male Caucasians collected urine before and 0-2, 2-4, 4-6, 6-8, 8-12, 12-16 and 16-24 h after a dose of 150 mg caffeine given in the framework of a phenotyping cocktail study. The metabolites 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X), and 1-methylurate (1U) were quantified with LC-MS/MS. The molar ratio (AFMU + AAMU)/(1X + 1U + AFMU + AAMU) was used as a NAT2 metric, while the ratio 1U/(1X + 1U) served as XO metric.
resultsThe NAT2 ratios were stable in the intervals 4-24 h after caffeine dosing. Mean intra-individual coefficients of variation were 11-23% starting 4 h post-dose, while inter-individual variability reached 37-75%. The XO ratios increased gradually by 14% from the 2-4 to the 16-24 h interval. The mean intra- and inter-individual coefficients of variation of XO activity were 3-18 and 7-10% respectively. No significant differences between study occasions were observed.
conclusionsAny sampling interval at least 4 h after caffeine dosing is suitable for NAT2 and XO activity assessments. XO activities can only be compared between volunteers and studies if the same urine collection schedule has been respected. The low intraindividual variability allows for sample sizes of 16 and 6 participants in crossover interaction studies of NAT2 and XO activity respectively.
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