Influence of Technological Parameters on the Size of Benzocaine Particles in Ointments Formulated on Selected Bases

Abstract

Compounding formulations, including semi-solid medication forms, must meet criteria related to specific stability and quality, during a period of their use. In suspension-type ointments, one of the criteria for assessment of their correct manufacturing is particle size, which in the compounding preparation cannot exceed 90 µm. An appropriate level of particle disintegration can be achieved via a selection of technological parameters and qualitatively compatible excipients. In this study, benzocaine ointments were prepared using a levigation process. The time of its application on the particle size of API in suspension ointments was evaluated. In parallel, the effect of mixing parameters and the co-solvent used on the precipitation of active substance crystals in emulsion ointments during the storage of these formulations for 28 days was investigated. Forty suspension and emulsion ointments were prepared using selected ointment bases: Pentravan®, Lekobaza, Lekobaza LUX, Eucerin Ointment I, Nourivan™ Antiox, Fitalite™, containing 2% benzocaine. Based on the results of the stability test, four formulations were selected to study the release kinetics of benzocaine in vitro. These formulations were characterized by the rate of release consistent with the Higuchi model, and the fastest rate of release occurred from the Eucerin-based emulsion ointment.