The antinociceptive effect of the aqueous extract of Zizyphus spina-christi root bark was investigated in mice and rats. Acetic acid-induced writhing, formalin and thermal (hot plate) tests were used. The extract (50 and 100 mg/kg, i.p.) showed a dose-dependent analgesic effect in all the tests used. Its i.p. LD50 in mice was 2236.07 mg/kg.
Department of Pharmacology & Toxicology, National Institute for Pharmaceutical Research and Development, Idu Industrial Area, P.M.B. 21, Garki, Abuja, Nigeria.