Effect of Three Liquid Additives on Diffusion of Atropine from Ointment Bases

Water, alcohol, and dimethyl sulfoxide were each incorporated at 1, 2, and 5% concentrations into four ointment bases containing atropine. The diffusion of drug from five samples of each base was determined at 20‐min. intervals for 2 hr. The diffusion process was zero order after 20 min. In the majority of instances, diffusion was significantly enhanced by the presence of the liquids. The concentration of liquid additive had significant effect in some instances; however, this effect was dependent on the type of base. Rate constants were calculated, and data were subjected to statistical analyses. The viscosity of each mixture was determined and, in some instances, appeared to correlate with the diffusion rates.