Introduction: Nigella sativa is considered to have antioxidant components though it is proposed to have hepatoprotective and nephroprotective effect.
Aim of the study: This study aimed to investigate hepatotoxic and nephrotoxic effects of sildenafil and to evaluate the role of Nigella sativa Linn oil in improving these effects and measure testosterone levels.
Materials and methods: Twenty eight male healthy domestic rabbits were randomly divided into 4 groups (7 animals for each) and gavaged by the studied substances for 28 days. Control group received 2ml/kg/day of gum acacia. Nigella sativa group received 2 ml/kg/day of Nigella sativa oil. Sildenafil group received 26 mg/kg/day of sildenafil citrate. Combined group received Nigella sativa oil followed immediately by sildenafil citrate daily in the previous doses.
Results: Sildenafil induced hepatotoxicity and nephrotoxicity as revealed by significant increase in ALT (452.25±60.23 versus 31.67±4.51, P<0.001), AST (183.75±37.21 versus 26.00±4.00, P<0.001), urea (55.00±3.65 versus 30.00±8.72, P=0.001) and creatinine (1.34±0.22 versus 0.83±0.21, P = 0.001) in sildenafil group than controls and histopathologically by  cyto-architectural distortions of the hepatocytes and centrilobular hemorrhagic necrosis and renal degenerative and atrophic changes. These toxic effects were ameliorated biochemically and histologically when sildenafil was administered with Nigella sativa oil in the fourth group. Moreover, the testosterone levels were improved in the combined group than in sildenafil group (19.46±0.90 versus16.71±1.16).
Conclusions and recommendations: Nigella sativa oil has a protective effect against hepatotoxicity and nephrotoxicity of sildenafil and increases testosterone levels in combination with sildenafil.