Abstract
1. The metabolism of papaverine was studied in vitro using the 9000 g fraction of rat liver. Apparent Km and Vmaxvalues were 1·6x10-5M and 34 nmol/g/min. Three monodemethylated metabolites were found by t.l.c. 2. Pre-treatment of rats with phenobarbital enhanced the activity of papaverine O-demethylase, whereas pre-treatment with 3-methylcholanthrene did not. Pre-treatment with SKF 525-A, or addition of SKF 525-A in vitro markedly inhibited the enzyme. 3. Pre-treatment of the rats with phenobarbital enhanced the biliary elimination rate of papaverine metabolites, whereas SKF 525-A pre-treatment slowed this elimination.