Effect of age on antipyrine metabolism in patients with gastric cancer.

The metabolism of antipyrine was studied in 19 male patients with gastric cancer. Three groups of subjects were chosen for the study: 4 patients 46--51 years of age (group 1), 8 patients 52--61 years old (group 2), and 7 patients 62--75 years old (group 3) matched for sex, smoking, alcohol intake, renal function, and liver function. The mean half-life (t 1/2) of antipyrine in group 3 (15.6 +/- 4.8 hr) was significantly longer than that in group 1 (8.1 +/- 0.9 hr, P < 0.01). Similarly, the mean metabolic clearance rate (MCR) in group 3 (246 +/- 78 ml/hr/kg) was significantly lower than that in group 1 (498 +/- 175 ml/hr/kg, P < 0.02). Significant correlations were observed between age and the t 1/2 of antipyrine (r = 0.592, P < 0.01) and between age and MCR (r = -0.499, P < 0.05). The plasma of 8 patients was tested for testosterone levels. Significant correlations were observed between plasma testosterone levels and both the t 1/2 of antipyrine (4 = -0.783, P < 0.05) and MCR (r = 0.912, P < 0.001). These observations indicate that drug-metabolizing ability might decline with age in cancer patients.