Dithiazanine iodide and tetrachloroethylene, alone and in various combinations, were tested for anthelmintic effect in an institutionalized population, both after single regimens and after dosing at regular intervals for an extended period. The results of the study are based on a total of 1,974 treatment regimens in 197 patients.
The use of single treatments of dithiasanine alone was effective against Trichuris trichiura but showed little or no effect on hookworm infections. Tetrachloroethylene alone in low dosages had a slight effect on hookworm and none on T. trichiura. Combining the two drugs did not improve the effectiveness against T. trichiura, but apparently did slightly improve the effect on hookworm.
Giving repeated dosages of the drugs at weekly, monthly, or quarterly intervals did not markedly improve the anthelmintic effect over the single use of similar regimens. Transmission of T. trichiura continued in all treatment groups, and in none was there any complete elimination of helminths.
The data conclusively demonstrated a reduced effectiveness of dithiasanine when used for repeated treatment of T. trichiura in the same patient. Reasons for this lesser effectiveness are not apparent.
Dithiasanine, while removing most of the T. trichiura when used as an initial treatment, did not clear the parasite from the groups treated nor eliminate its transmission when repeated dosages were given over an extended period. Addition of small amounts of tetrachloroethylene to the regimens improved the effect against hookworm but not against T. trichiura.
Nine of 14 Ascaris lumbricoides infections were eliminated. No effect on two Hymenolepis nana infections were seen.
Present address: Laboratory of Parasite Chemotherapy, NIAID, National Institutes of Health, Bethesda, Maryland.