PREDOMINANCE OF SLOW ACETYLATORS OF N-ACETYLTRANSFERASE IN A HMONG POPULATION RESIDING IN THE UNITED-STATES

Pharmacogenetics can be an important determinant of pharmacologic resp onse. To learn more about interpopulation differences in drug metaboli sm between ethnically diverse populations of subjects cared for by an International Clinic, a study was conducted to describe the prevalence of fast or slow acetylators of N-acetyl transferase (NAT2) in a popul ation of Hmong residing in Minnesota. Ninety-eight healthy Hmong refug ees from Laos volunteered to take caffeine as an oral probe drug to es tablish acetylator phenotype. Participants were classified as either r apid or slow acerylators based on the urinary molar ratio of select me tabolites of caffeine. Assignment of phenotype was based on results fr om analysis of urine collected subsequent to ingestion of caffeine, Th e ratio of 5-acetylamino-6-formylamino-3-methyluracil (AFMU) to the co mbined products of the 7-demethylation pathway of paraxanthine [AFMU, 1-methylxanthine (1X), and 1-methylurate (1U)] formed the basis for th is determination. A probit plot of the data collected in our subjects qualified a metabolic ratio of 0.34 as an acceptable cut point for phe notype assignment, Participants with an AFMU/(AFMU + 1X + 1U) ratio of <0.34 were classified as slow acetylators and all others as rapid ace tylators. Analysis of the data su distribution with an excess (74.5%) of slow acetylators in the population, The predominance of slow acetyl ators found in the Hmong contrast with the prevalence of slow acetylat ors seen in other ethnic groups, These findings may have important cli nical implications given the large number of Hmong treated each year i n our International Clinic and the increasing use of medications metab olized by NAT2 in this population.