Therapeutic field trial of a macro- and microfilaricidal agent in canine filariasis.

The discovery in 1973 of a synergistic effect of the arsenical compound F 151, a macrofilaricide, and the benzimidazole compound HOE 33258, a microfilaricide, led to the preparation of the reaction product of F 151 and HOE 33258 (in the proportion 1 mol to 2 mol, respectively), which was designated by the letter E. This compound E proved to be an effective macro- and microfilaricidal agent when administered subcutaneously in a single well-tolerated dose to dogs that were naturally infected with Dirofilaria immitis.