Anti-inflammatory, antinociceptive, and gastric effects of Hypericum perforatum in rats

The pharmacological activity of Hypericum perforatum was assessed using models of inflammation, nociception, and gastric mucosal injury in rats. H. perforatum was given systemically as well as orally. When administered systemically, H. perforatum (50-300 mg/kg, s.c.) produced a dose-related and significant inhibition of the edematogenic response to s.p. injection of carrageenan. The percentages of maximal inhibition by the above doses were 53.7, 61.3, and 75.3%, respectively (compared to 90% after 50 mg/kg fluoxetine and 60.7% after 72 mg/kg etodolac). In tests of nociception, H. perforatum, administered orally, displayed antinociceptive activity in the tail electric stimulation and hot plate tests. The antinociceptive activity was observed with 25 mg/kg and a maximal increase in hot plate latency by 50% (compared to 73.2 and 77.8% increases by 5 or 10 mg/kg fluoxetine, respectively). In contrast, the acetic acid-induced (0.6%, i.p.) writhing was significantly reduced by fluoxetine or etodolac, but not H. perforatum. Also, the nociceptive response caused by i.p. injection of capsaicin (1.6 microg/paw) was unaffected by H. perforatum, but reduced by fluoxetine. Injection of H. perforatum (50, 125, or 250 mg/kg, s.c.) to pylorus-ligated rats, decreased gastric acid secretion, but increased indomethacin-induced gastric mucosal lesions dose dependently. These results demonstrate that H. perforatum exhibits antiedematogenic and antinociceptive properties, which may be of value for the management of inflammatory painful conditions. The agent, however, causes gastric irritation and may aggravate that of NSAIDs.