A noninvasive method for the study of hepatic drug metabolism in rodents: aminopyrine metabolism in rats.

A rapid, sensitive, and simple high-performance liquid chromatography method is described for the direct analysis of aminopyrine in saliva. The detection limit was found to be 12 ng/ml of sample. Accuracy and precision were maintained with as little as 1 microliter of saliva. Thus the rate of elimination of aminopyrine has been monitored noninvasively in rats. The aminopyrine half-life was found to be 59.5 +/- 10.5 (SD) min. The half-life was independent of an aminopyrine dose between 50 and 200 mg/kg. In rats single intraperitoneal doses of SKF 525-A (20 mg/kg) produced increases in aminopyrine half-life and salivary aminopyrine concentration. Phenobarbital induction lowered the aminopyrine half-life to 33.2 +/- 8.5 min and the salivary aminopyrine concentration.