This study evaluated the haematotoxic effects of Nevirapine and the role of Kolaviron, a potent antioxidant from Garcinia kola as an adjuvant. Forty eight adult male Sprague-Dawley rats were used in this study. The animals were divided into eight groups, A-H (with 6 rats per group). Group A animals received normal saline as the control; Group B were given Nevirapine (1.54 mg/kg); Group C received Kolaviron (200 mg/kg); Group D were treated with vitamin C (250 mg/kg); Group E were given Nevirapine 1.54 mg/kg + Kolaviron 200 mg/kg; Group F were given Nevirapine and Vitamin C at concentrations of 1.54 and 250 mg/kgbw; Group G were given Nevirapine (1.54 mg/kg)+Kolaviron for 28 days (and discontinued) serving as a withdrawal group; Group H received corn oil (vehicle for Kolaviron). All treatments were by oral gavage. Blood samples were collected by cardiac puncture at the end of experiment and various haematological parameters assessed. While there was weight gain in all experimental groups this was least in vitamin C + Nevirapine treated animals. Statistically significant declines in Hb levels (P< 0.05) were seen in group E whereas PCV were elevated in groups B, D, and F but these were not significant (p>0.05). In addition there was a statistically significant increase (P<0.01 and 0.05) in platelet levels in groups B, G and H respectively while MPV was high in group B. Differential WBC showed leucopaenia mostly with marked significant decline in neutrophils in Nevirapine alone and with adjuvant Kolaviron or vitamin C. In conclusion, there is evidence that Kolaviron does not mitigate the ravages caused by nevirapine on haematological parameters, hence caution is advised in its adjuvant use. Key words: Nevirapine, kolaviron, haematology, leucopaenia.

Keywords: Nevirapine, kolaviron, haematology, leucopaenia.