Diphenhydramine and levofloxacin combination therapy against antimicrobial resistance in respiratory tract infections.

Antibiotics are in use since decades to treat various infections caused by Gram-positive and Gram-negative bacteria such as and . Diphenhydramine, an H1 receptor blocker possesses a weak antibiotic action but when combined with other antibiotics may potentiate their antibacterial activity. This study investigated antibacterial activity of diphenhydramine when used alone and in combination with levofloxacin against methicillin-resistant  and . The combined antibacterial effect of the drugs against bacteria showed a fractional inhibitory concentration index of ≤0.5, in other words, synergism. No cytotoxicity was observed as percentage cell viability was >50%. The combination of diphenhydramine and levofloxacin exerted antibacterial activity, and was not found to be cytotoxic when given in combination against and .