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

Background:Antibiotics are in use since decades to treat various infections caused by Gram-positive and Gram-negative bacteria such as Staphylococcus aureusand Pseudomonas aeruginosa. Diphenhydramine, an H1 receptor blocker possesses a weak antibiotic action but when combined with other antibiotics may potentiate their antibacterial activity. Materials & methods:This study investigated in vitroantibacterial activity of diphenhydramine when used alone and in combination with levofloxacin against methicillin-resistant S. aureusand P. aeruginosa. Results: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%. Conclusion:The combination of diphenhydramine and levofloxacin exerted antibacterial activity, and was not found to be cytotoxic when given in combination against P. aeruginosaand S. aureus.