Abstract
1. The effect of β-naphthoflavone (BNF), given i.p. (n = 9) and orally (n = 9), on the metabolism of antipyrine and metronidazole was investigated in rats.
2. The clearances of antipyrine and metronidazole were determined on a single saliva sample. The rates of formation of antipyrine and metronidazole metabolites were determined from a 20 h urine sample and saliva clearance.
3. Administration of β-naphthoflavone i.p. was significantly more effective than oral dosage on the induction of antipyrine and metronidazole metabolism (p<0.05).
4. The capacity of extrahepatic tissues to metabolize antipyrine and metronidazole was quantitatively assessed in rats with and without pretreatment with β-naphthoflavone immediately after sham operation or 70% partial hepatectomy (n = 40).
5. Antipyrine and metronidazole clearances correlated with liver weight in induced and non-induced rats. Linear regression of antipyrine and metronidazole clearances did show a non-significant Y-intercept (p>0.05), indicating a negligible extrahepatic metabolism in both induced and in non-induced rats.
6. From a quantitative point of view this study indicates that induction of extrahepatic cytochrome P450 metabolism of antipyrine and metronidazole is negligible.