Studies on the percutaneous absorption of paeonol in experimental animals by a radioactive tracer technique

Studies on in vivo percutaneous absorption of paeonol (2-hydroxy-4-methoxyacetophenone: I) in rabbits, guinea pigs, and rats were carried out by a radioactive tracer technique. Hydrophilic ointment (specific activity: 376 Bq (0.01016 microCi)/mg) containing I[carbonyl-14C] was applied for 24 h by occlusive dressing treatment on the shaven back of experimental animals. Then, the 14C-activity in urine, which is the dominant excretion route, was determined for 8 days. Percentage excreted within 24 h after application to rabbits, guinea pigs, and rats were 42.8%, 46.5% and 52.0%, respectively. Urinary metabolites were identified as 2,5-dihydroxy-4-methoxyacetophenone, resacetophenone, and substrate I in all the case.