Antinociceptive Effects of Newbouldia laevis (P. Beauv.) Stem Bark Extract in a Rat Model

Various parts of Newbouldia laevis (fam. Bignoniaceae) are used for pain and several inflammatory conditions in Ghana. This study presents the effect of a hydro-alcoholic extract of N. leavis stem bark in formalin-induced pain, a model of neuropathic pain, in rats. Morphine (1-10 mg kg ^-1 i.p) and stem bark extract of N. laevis (10-300 mg kg ^-1 p.o.),dose-dependently decreased both phases of the formalin-induced nociceptive behaviour. Nocifensive response for morphine was four fold higher in the first phase (ED _50; 7.59 ± 0.63 mg kg ^-1 ) compared to the second (ED ₅₀ ;7.59± 2.26) ; however the response for the extract was similar in both phases (ED _50; first phase 28.28±7.02; ED _50; second phase 25.07 ± 5.83). Diclofenac (10-100 mg kg ^-1 ) was effective only in the second phase (ED ₅₀ 33.24± 5.20). The potency of the drugs was in the order; morphine > extract > diclofenac for the first phase and morphine > extract = diclofenac for the second phase. The results from this study show that N. laevis extract has central and peripheral analgesic properties and thus adds credence to its traditional uses.