[Microbiological assay of some phenothiazine derivatives using different strains of Bacillus subtilis].

This paper deals with the microbiological assay of chloropromazine, levomepromazine and promethazine, whose bacteriostatic power was measured in the diffusion test against four different strains of Bacillus subtilis. The four strains proved to be equally sensitive to solutions of phenothiazine derivatives containing more than 0.5 mg/ml. There was no difference between the four strains as referred to the median percentual error in the chlorpromazine determination. The median percentual error has been very high (around 20%) in the levomepromazine determination using Bacillus subtilis ATCC 9945. When promethazine was used against the four strains of Bacillus subtilis a very high percentual error (around 20%) has been obtained, therefore, they are not recommended for the promethazine determination.