Introduction: Patients treated in intensive care units usully  require the intravenous  co-administration of drugs with different mechanism of action for   acute and chronic illness, infection, pain relief, and sedation. Non-antibiotics may have synergistic antimicrobial effect of an antibiotic in vitro (1). The antifungal synergism of amiodaron and an azole compound for Candida albicans is already known (2). In this study we investigated the impact of amiodarone on the bactericidal effect of antibiotics.
Methods: Amiodarone infusion was contaminated with low colony forming units (cfu) of standard bacterial strains (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922,  Pseudomonas aeruginosa ATCC 27853) separatelly and bacterial count was checked at intervals. Minimal  inhibitory concentration (MIC) of the drugs were determined and compared with serum concentration. Checkerboard method was used for investigation of combined effect of amiodarone and antibiotics with different mechanism of action.   We determined the fractional inhibitoty concentration index what is the predictor of synergism.
Results: 5x103 cfu bacteria did not survive in amiodarone infusion after 15 minutes. MIC levels of both drugs are higher than the serum concentration of drugs. There were synergistic antimicrobial effects of combined amiodarone and oxytetracycline against standard bacterial strains.
 Conclusions: The non-antibiotics might have antimicrobial synergistic effect with some antibiotics, thus they may contribute to the killing of pathogens when they are co-administrated. Further research is required  whether there is any in vivo synergistic effect resemble for  the above in vitro results. 
References: (1) Nat Chem Biol 2011; 7: 348. (2) J Med Microbiol  2008; 57:457.

Amiodarone and tetracyclines has synergistic antibacterial effect