The inhibitory effect of Hypericum perforatum extract on morphine withdrawal syndrome in rat and comparison with clonidine

The effects of Hypericum perforatum (St John's wort) on morphine withdrawal syndrome and comparison with clonidine have been investigated in morphine‐dependent rats. Adult male Wistar rats were subjects. The frequencies of withdrawal behavioral signs (rearing, teeth chattering and jumping) induced by naloxone challenge were demonstrated in morphine dependent rats receiving Hypericum perforatum extract (HPE), saline or clonidine. The withdrawal behavioral manifestations in rats were inhibited significantly by chronic co‐administration of Hypericum perforatum extract or clonidine with morphine. This study showed that clonidine was more effective than HPE at a dose of 0.4 mL/200 g and there was no significant statistical difference between the mean frequency of withdrawal signs of HPE at a dose of 0.8 mL/200 g compared with clonidine (0.2 mg/kg i.p.) but at a dose of 1.2 mL/200 g of HPE was significantly stronger than clonidine in attenuation of the morphine withdrawal syndrome. The findings suggest that HPE is capable of reducing the symptoms of opiate withdrawal and its effectiveness may be equivalent to clonidine in reducing the opiate withdrawal syndrome and may have human therapeutic potential. Copyright © 2009 John Wiley & Sons, Ltd.