Abstract
It has been previously reported that acemetacin (ACM), the carboxymethyl ester of indomethacin (IND), is almost completely metabolized to IND in vivo. In the present study, the anti-inflammatory effects of ACM were compared with those of IND. ACM showed inhibitory effects on vascular permeability induced by phenylquinone. ACM inhibited carrageenin, kaolin, and nystatin edema dose-dependently and the ED30 in the carrageenin edema test was 2.8 mg/kg. Inhibitory effects of ACM on carrageenin edema was not influenced by adrenalectomy or repeated administration of ACM. ACM also inhibited ultraviolet erythema at 5 mg/kg. Furthermore, ACM significantly inhibited granuloma formation at 2.5 mg/kg/day. The ED30 for the therapeutic effect on established adjuvant arthritis was 0.33 mg/kg/day. These anti-inflammatory effects of orally administered ACM were equivalent to or somewhat weaker than those of IND at an equimolar dose. Platelet aggregation was inhibited when ACM was given orally to rats and the activity of ACM was similar to that of IND. On the other hand, the effects of locally administered ACM on carrageenin and kaolin edema were markedly less potent than those of IND. In addition, inhibitory effects on prostaglandin synthesis and platelet aggregation in vitro were significantly weaker than those of IND. These results suggest that the observed anti-inflammatory effects of orally administered ACM are not due to its inherent action, but due to its metabolite, IND.
