Impaired learning and memory: a fallout of metronidazole induced neurotoxicity

Context: Metronidazole, an old warhorse in treatment of anaerobic, parasitic as well as bacterial infections in human and veterinary medicine has been observed to have neurotoxic adverse effects. An increase in the existing knowledge on the mechanisms of metronidazole-induced neurotoxicity is necessary. Aim: To evaluate the effects of metronidazole on memory and learning in adult rats. Methods and material: Eighty adult rats were allotted to 4 groups (n=20). Group 1 was given 5 mL/kg 0.5% Tween-80®, group 2 was treated with 50 mg/kg metronidazole, group 3 was given 1 mg/kg risperidone, group 4 was treated with metronidazole 50 mg/kg + risperidone 1 mg/kg. All drug administrations were done daily for 28 days using the oral route. On the 28th day the rats were exposed to tests that evaluated cognitive function like the hole-board, Morris water maze and Y-maze test. Statistical analysis used: One-way ANOVA followed by Dunnet’s post hoc test for multiple comparison. Statistical differences were considered significant at p<0.05. Results: Metronidazole impaired memory acquisition and learning, and reduced reference memory index (RMI) on the hole board, increased the escape latency in the Moris water maze, and reduced percentage alternation and spatial recognition memory in the Y-maze (p<0.01). Co-administration of metronidazole with risperidone reversed all the memory and learning deficits in the treated rats Conclusion: In conclusion, it is suggested that metronidazole induces cognitive dysfunction by stimulating 5-HT2A receptors in the CNS.