Antimicrobial potentiality of the thioxanthene flupenthixol through extensive in vitro and in vivo experiments

The antipsychotic thioxanthene flupenthixol, possessing a trifluoromethyl substituent at position 2, exhibited a distinct antibacterial property against 352 strains of bacteria from 3 Gram-positive and 13 Gram-negative genera. The minimum inhibitory concentration (MIC) of flupenthixol was determined by the National Committee for Clinical Laboratory Standards agar dilution method. MICs ranged from 10-100 microg/mL in most of the strains, whilst some strains were inhibited at even lower concentrations. The mode of action of this drug was found to be bacteriostatic against Staphylococcus aureus and Vibrio cholerae. In the in vivo experiments, this drug was capable of contributing significant protection (P < 0.001) to a Swiss strain of white mice challenged with 50 median lethal dose of a mouse-virulent strain at a drug concentration of 15 microg/mouse. In addition, flupenthixol remarkably reduced the number of viable bacteria in organ homogenates and blood of mice treated with this drug.