Antibacterial activity of naltrexone and its combination with ciprofloxacin against Gram negative and Gram positive bacteria

Naltrexone, an opioid receptor antagonist, is commonly used in the treatment of alcoholism. Studies about the antibacterial activity of naltrexone are limited. In our study, we aimed to evaluate the antibacterial and synergistic activities of naltrexone against Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603. The results showed promising antibacterial activity against all tested pathogenic bacteria. Additionally, checkerboard assays revealed additive activity against S. aureus when combined with ciprofloxacin. Collectively, the data from our study suggest that naltrexone can further be used as a potential antibacterial source alone or in combination with other antibiotics in the treatment of bacterial infections.