[Drug hydroxylation disorders (debrisoquin type) in a random sample of the Swiss population]

The hydroxylation phenotype was determined in a sample of the Swiss population consisting of 222 normal unrelated subjects (131 women, 91 men). Following oral administration of a single dose of 19 mg debrisoquine, urine was collected for 8 hours. Urinary concentrations of parent compound and its major metabolite (4-hydroxydebrisoquine) were measured with GLC and their molar ratio ("metabolic ratio", MR) was calculated and plotted as a frequency distribution histogram. The frequency distribution of the MR was clearly bimodal, exhibiting two clusters of MR's of 0.1 to 1.0 and 20 to 100, respectively. Using probit analysis, the antimode was found at an MR of 12.6 Consequently, 22 subjects (16 women, 6 men), representing 10% of the population studied, were, with an MR of greater than 12.6, considered to be poor hydroxylators (PM). The families of two subjects, established as PMs in the population study, were also investigated. One family was found to be the first known pairing of homozygous PM parents with all 6 offspring exhibiting the PM phenotype. In both families the pattern was consistent with an autosomal recessive mode of inheritance for the two alleles E (extensive) and N (none) respectively. Clinical consequences of the PM phenotype known to date are summarized. Since some drugs typically used for longterm treatment (such as perhexiline, phenytoin, nortriptyline, guanoxan) are subject to the same hydroxylation pathway, PM patients are likely to be at higher risk of drug toxicity. This relationship has been well documented for perhexiline-induced neuropathy. Conversely, it is conceivable that with the use of prodrugs which have to be hydroxylated to the active compound, PM subjects might turn out to be "non-responders".