A comparison of the physicochemical properties and a sensory test of Acyclovir creams.

In external medicine, types and ratios of additives are not necessarily the same for well-known brand-name drugs and generic drugs. This study sought to compare the physicochemical properties and sensory test results of a brand-name Acyclovir (ACV) cream and two generic ACV creams. Near-infrared (NIR) spectroscopy revealed changes in absorption spectra attributed to differences in the oil and water content of the 3 creams. In addition, ACV-B and ACV-C had similar NIR absorption spectra. Microscopic examination revealed crystallization in each of the creams and droplets in ACV-C. Powder X-ray diffraction measurement revealed diffraction peaks due to ACV for ACV-A and ACV-B. Assessment of viscoelasticity indicated that stress of subjection to 35 °C caused no changes in the viscoelasticity of ACV-B and ACV-C in comparison to stress of subjection to 25 °C but it did cause the viscoelasticity of ACV-A to decrease. ACV-A had a greater tolerance to stress and a higher viscosity, tan δ, and yield value than the other 2 creams. Results of a sensory test revealed significant differences in adhesiveness, spreadability, and feel for ACV-A in comparison to ACV-B and ACV-C. Thus, differences in the viscosity and elasticity of the creams due to differences in types and ratios of additives were noted. These differences are surmised to be differences in physical properties. In addition, results suggested that viscoelasticity and spreadability in the sensory test reflected differences in physical properties.