ELIMINATION STUDIES OF ANTIPYRINE AND ITS METABOLITES IN HEALTHY SAUDI-ARABIANS

1 We measured the antipyrine clearance in 18 healthy Saudi subjects and determined the urinary excretion of three of its metabolites: 4-hydroxyantipyrine (4-OH AP), norantipyrine (NOR AP) and 3 hydroxymethylantipyrine (3-OHM AP) in 21 subjects. 2 The mean +/- SD of the antipyrine clearance was 2.4 +/- 1.1 h(-1) (range 1.0-5.5 1 h(-1)) and the corresponding value per kg body weight was 0.6 +/- 0.2 ml min(-1) kg(-1). Urinary excretion of antipyrine (AP), 4-OH AP, NOR AP and 3-OHM AP expressed as a percentage of the oral dose of antipyrine given was 2.8 +/- 2.2, 14.5 +/- 6.9, 12.3 +/- 5.6 and 7.6 +/- 3.2 respectively. 3 Compared to Africans, Saudis preferentially metabolize AP to NOR AP and compared to Caucasians to 3-OHM AP, rather than to 4-OH AP. These discrepancies may reflect age differences between the study populations rather than genetic or ethnic variations.