Synergistic effects of monensin in combination with permethrin or neomycin on neuronal activity

Drug combinations have the potential to produce novel and unpredictable responses on nervous tissue. This study was designed to test the hypothesis that the effects of combinations of monensin (an ionophore antibiotic) and either neomycin (an aminoglycoside antibiotic) or permethrin (synthetic pyrethroid) are synergistic. Effects of the drug combinations upon the electrical properties and membrane activities of an in vitro sensory neuron preparation were found to be greater than expected from addition of the effects of the same drugs acting individually, indicating synergism and thus supporting the hypothesis. It was concluded that drugs acting at different neuronal membrane sites and applied in combination produce unpredictable responses. Such drug combinations behave as if they were novel drugs.