Amoebicidal activity of dichloro-N-2-hydroxy-ethyl-N-p-methylsulphonylbenzylacetamide and some related compounds.

Compounds structurally related to known amoebicidal dichloroacetamides were examined for activity against Entamoeba histolytica by an in vivo/in vitro method and an experimental caecal infection in weanling rats. Dichloro-N-2-hydroxyethyl-N-p-methylsulphonylbenzylacetamide (M&B 4321) was the first compound of this series to show high amoebicidal activity against experimental E. histolytica infections in young rats. Some subsequent compounds, particularly several closely related to M&B 4321, had a similar effect. Comparative experiments on both activity and toxicity were carried out on M&B 4321 and diloxanide, since the latter compound had already been administered safely to man and had shown good activity against non-dysenteric amoebiasis. The two compounds were found to be generally similar in properties. Other compounds which were of the same order of activity were discovered later, but as none had much more activity than M&B 4321 they were not studied in detail. A small trial against dysenteric amoebiasis showed that M&B 4321 was amoebicidal in man but that the cure rate was disappointing.