Laboratory and field trials were conducted to enhance the efficiency of zinc phosphide bait against rats using Spasmomen drug (octylonium bromide) as an antispasmodic agent. Spasmomen was tested alone and mixed with zinc phosphide bait at different concentrations using non and free choice feeding methods against albino rat and wild Norway rat, Rattus norvegicus. Results indicated that Spasmomen at rate 0.05% when added to zinc phosphide bait at level 0.25 and 0.125% achieved 43.5 and 46.3% acceptance, respectively and enhanced the mortality from 50 to 75%. The field performance was in harmony with laboratory results as Spasmomen enhanced the population reduction percentage of Norway rat from 17.4 to 56.0 % and from 66.0 to 71.2% when added to zinc phosphide bait 0.125 and 0.25%, respectively. The antispasmodic action of Spasmomen prevent the pain resulting from zinc phosphide treatment. This action lead rats to accept the bait of zinc phosphide and eat more causing high mortality percentage.