Evaluation of Mosquito Repellent Formulations

□ N,N-Diethyl-m-toluamide was formulated with several acrylate polymers in ethanol solution and various silicone polymers in 2-propanol suspension; the ratio of polymer to N,N-diethyl-m-toluamide(I) was varied. Formulations that had drying times of <10 min were evaluated for film hardness and elasticity. Contact angles made by water on films cast from the formulations were measured when such films were uniform. For the acrylate formulations, containing polymers that are solid at room temperature, the presence of I increased drying times; decreased film hardness and elasticity resulted from decreasing the ratio of polymers to I. Lower contact angle with water resulted from decreasing the ratio of acrylate polymer to I. However, this effect was less pronounced with the lower molecular weight acrylate polymer formulations. Films cast from the silicone formulations had low contact angles with water. In addition, formulations of repellents, ethohexadiol and N,N-diethyl-p-toluamide, each in combination with a silicone polymer, were evaluated. Films with short drying times, high contact angle, and measurable hardness could be cast from the N,N-diethyl-p-toluamide–silicone formulations due to the film-forming ability of the repellent itself. The physical properties of the ethohexadiol–silicone formulations were similar to the I–silicone formulations. Selected formulations received preliminary evaluation for duration of effectiveness against Aedes aegypti mosquitoes in vitro and in animal test systems. Except for one formulation of I with a lower molecular weight acrylate polymer, these formulations did not enhance the duration of effectiveness of I on hairless dogs. The in vitro ED50 of the test repellent for A. aegypti was significantly enhanced in 5 of 15 formulations tested. The 4-hr ED50 of the test repellent on white mice was significantly enhanced in 6 of 15 formulations tested. Keyphrases Repellents, mosquito—film hardness and elasticity evaluation for N,N-diethyl-m-toluamide–acrylate polymer formulations; N,N-Diethyl-m-toluamide—formulation with acrylate polymer, evaluation for film hardness and elasticity in mosquito repellents; Polymers—N,N-diethyl-m-toluamide formulations, evaluation for film hardness and elasticity in mosquito repellents