TY - JOUR T1 - Effect of Age on in Vitro Triazolam Biotransformation in Male Human Liver Microsomes JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 874 LP - 879 DO - 10.1124/jpet.103.059311 VL - 308 IS - 3 AU - Kiran C. Patki AU - Lisa L. von Moltke AU - Jerold S. Harmatz AU - Leah M. Hesse AU - Michael H. Court AU - David J. Greenblatt Y1 - 2004/03/01 UR - http://jpet.aspetjournals.org/content/308/3/874.abstract N2 - We studied age-related changes in enzyme kinetic parameters in human liver microsomes (HLMs) in vitro, using triazolam (TRZ), an index of CYP3A activity. HLMs were prepared from male livers from four age groups, n = 5 per group: A (14–20 years), B (21–40 years), C (41–60 years), and D (61–72 years). Mean Vmax values in groups B and C for both 1-hydroxytriazolam (1-OH-TRZ) and 4-hydroxy-triazolam (4-OH-TRZ) formation were significantly greater as compared with groups A and D individually, as well as the net intrinsic clearance (sum of the two pathways). The mean net intrinsic clearance (Clint) values were 25.2, 89.8, 78, and 20.6 nl/min/mg protein in A, B, C, and D, respectively. TRZ Clint correlated well with total CYP3A content (rs = 0.84; P < 0.0001). Testosterone (TST) inhibited 1-OH-TRZ formation and activated 4-OH-TRZ formation in all age groups, with no significant differences among the groups; this suggests that the drug-drug interaction potential using TRZ and TST as index CYP3A substrates may not change with age. Reduced Vmax and Clint for TRZ hydroxylation and CYP3A protein in livers from elderly men suggest reduced CYP3A gene expression in this group. The American Society for Pharmacology and Experimental Therapeutics ER -