The effects of ageing on aminopyrine and caffeine breath tests in the rat

The influence of ageing on demethylation of 14C-aminopyrine (AP) and 14C-caffeine (Caf) in Wistar littermate rats was studied serially using the 14CO2-breath test. In both sexes, the elimination half-life (t1/2) of 14C-AP fell from a mean of approximately 75 min when weaned at 17 days to 45 min at maturity (49 days); thereafter t1/2 became prolonged, being most prolonged (82 min) in elderly male rats (210 days). Similarly, t1/2 of 14C-Caf was also prolonged with ageing. These studies using in vivo and longitudinal techniques indicate the importance of ageing on hepatic demethylation.