[Biological assay of anthelmintic drugs. Determination of DE 50].

Experiments on ivermectine, thiabendazole and levamisole were performed by using the Nippostrongylus brasiliensis rat model. The aim of the experiments was to study the 50% as well as 99.5% doses of the above anthelmintics. Besides this a relative evaluation of drugs was also carried out and different dose efficiencies were compared by keeping one anthelmintic as a standard. The results were obtained on the following experimental conditions: homogeneity of the group of rats (age, weight and sex), uniform infestation in all the animals (3000 larvae at day zero), administration of anthelmintics was done on day 6 and autopsy was performed on the 9th day of infection. The effectivity of anthelmintic is essentially based on the mortality of the adult worms. The mathematical expression is obtained on the basis of logarithmic values of the doses and probit percentage analysis. The graph obtained between dose vs efficiency is a straight line, so the value of DE 50 can be calculated using this straight line. The normal distribution of worms exposed to a dose was verified which justifies the statistical interpretation.