Abstract

Antihistamines belong to H1 receptor antagonist class of drugs. Pharmacologically they are classified into two categories namely first generation, mostly sedating in nature and second generation, which are less sedating and quite selective in activity. Widespread uses of antihistamines were found during microbial infections of various types. The utmost deliberate effort in comprehending the actions of antihistamines within the extent of antimicrobials forms the basis of the investigation. The antimicrobial activity of antihistamines explored by previous researchers helped in determining the minimum inhibitory concentration of cetirizine against 51 strains of bacteria. The antiallergic drug cetirizine showed significant in vitro antimicrobial activity against 51 strains of bacteria belonging to 5 Gram-positive and 4 Gram-negative genera. The minimum inhibitory concentration of the drug determined both by agar dilution and broth dilution method ranged from 200-2000 μg/ml against most of the bacteria tested. Cetirizine was bactericidal in action in vitro on both Gram-positive and Gram-negative bacteria. In vivo experiment with this drug proved that it could offer significant protection to mice challenged with a virulent bacterium Salmonella typhimurium NCTC74. Thus, cetirizine has immense potential to be developed as an antibacterial agent. Therefore the present study would help in corroborating future prospects in disseminating efficacious use of cetirizine in mitigation of microbial infections.