Influence of Liquid Paraffin, White Soft Paraffin and Initial Hydration on Viscosity of Corticosteroid Cream

Purpose: To ascertain the influence of paraffin, white soft paraffin and pre-hydrated white soft paraffin on the viscosity of a cream formulated with a corticosteroid.
Methods: The formulations were prepared via homogenization with variable velocity in the range 3300 - 4000 rpm. Individual series of preparations contained the same proportion of macrogol cetostearyl alcohol, cetyl alcohol, stearyl alcohol, sorbitan stearate, propylene glycol, metyl parahydroxybenzoate, propyl parahydroxybenzoate and water. The semi-solid preparations were assessed by viscometric and microscopic methods.
Results: The viscosity of the samples measured ranged from 13050 to 15660 mPas. The particles in dispersed phase sized from 15 to 90 μm. Within the multiple emulsion, the continuous phase included fine particles with diameter < 5 μm. Change of the liquid paraffin used from Ondina 934 to Vara 600P significantly decreased the viscosity of the formulation. Several phases within the formulations were distinguished microscopically. Increased viscosity was observed in formulations with increasing proportion of white soft paraffin.
Conclusion: Both the ratio of liquid paraffin to white soft paraffin, as well as the initial hydration of white soft paraffin influenced the viscosity of the cream as well as the diameter of particles in the dispersed phase.

Keywords
Cream; Ointment; Paraffin; Emulsion; Dispersion; Viscosity; Particle diameter