Original Article: PDF OnlyInterindividual variability of coumarin 7-hydroxylation in healthy volunteersRautio, Arja1; Kraul, Holger1,2; Kojo, Anneli3; Salmela, Erja1; Pelkonen, Olavi1Author Information 1Department of Pharmacology and Toxicology, University of Oulu, Kajaanintie 52D, SF-90220 Oulu, Finland 2Permanent address: Department of Clinical Pharmacology, University of Jena, 6900 Jena, Germany 3Department of Pharmacology and Toxicology, University of Kuopio, SP-70211 Kuopio, Finland Pharmacogenetics: October 1992 - Volume 2 - Issue 5 - p 227-233 Buy Abstract A test designed to estimate the extent and rate of formation of 7-hydroxycoumarin¶ by measuring the urinary excretion of the metabolite in humans after administering 5 mg coumarin was developed. Coumarin was rapidly metabolized after oral administration and more than 95% of the 7OHC formed was excreted in 4h. The total amount of 7OHC formed was 64±5% (mean ± SD, variation 20-100%) of the dose given. The percentage of 7OHC excreted in 2 h, as compared with the 7OHC excretion in 4 h, was found to be a constant and stable individual characteristic for the rate of the formation of 7OHC (‘2 h coumarin test’). In 110 volunteers, there was a great interindividual variability in the extent and rate of 7OHC formation. Four individuals had relatively ‘slow’ coumarin test values (50-60%), but much larger populations would be needed for the demonstration of polymorphism. © Lippincott-Raven Publishers.