Herbs are often co-administered with orthodox drugs, raising the potential for herb-drug interactions. This study investigated the pharmacological interaction between ethanol extract of Moringa oleifera
(MOE) leaves and metformin co-administered to diabetic Wistar rats. Diabetes was induced in rats by administration of 150 mg alloxan/kg body weight intraperitoneally. A dose-response study for MOE at doses of 100-2000 mg/kg body wt. was carried out. A plot of percentage glycaemic reduction at 4h post-treatment versus log dose was used to estimate the median effective dose (ED50
). Nine (9) groups of rats were used for the interaction study. Groups I and II served as normoglycaemic and diabetic controls respectively and received 1ml Normal saline. Diabetic Groups III-V received 375, 750 and 1500 mg/kg MOE respectively. Groups VI-VIII also diabetic received the same doses of MOE respectively but co-administered with a fixed dose of metformin (150 mg/kg). Group IX received metformin (150 mg/kg) alone. Fasting blood sugar (FBS) was monitored weekly and blood samples collected on day 28 for protein and lipid profile assay. The MOE/metformin co-administered groups showed greater antihyperglycaemic activity (p<0.001) than the MOE and metformin alone groups. Significant increases in serum levels of cholesterol, TG and LDLC with the decrease in HDLC levels in the alloxan induced diabetic rats were reversed in MOE (p<0.01) and MOE/metformin (p<0.001) administered groups. These findings indicate that MOE/Metformin co-administration produced additive anti-hyperglycaemic and hypolipidaemic effects compared to either MOE or Metformin alone and may be useful in the therapeutic management of diabetes mellitus that is associated with dyslipidaemia.