Some factors affecting the microencapsulation of pharmaceuticals with cellulose acetate phthalate

Phase diagrams were prepared to indicate the region of microcapsule formation for the following system: cellulose acetate phthalate, light mineral oil, acetone: 95% ethanol solvent, and sorbitan monooleate. The microencapsulation of pharmaceuticals having widely different solubility properties was carried out. Various factors affecting microencapsulation, namely trituration, order and time of addition of the pharmaceutical, core size, and the core to coat ratio, were investigated. The evidence for a mechanism of microencapsulation is also presented. The phase diagrams showed that microcapsules readily formed when the cellulose acetate phthalate concentration was in the 0.93-3.85% range and the polymer solvent concentration was in the 7-16% range. Aggregation of microcapsules was minimized at low solvent concentrations. Pharmaceuticals could be microencapsulated regardless of their solubility in the polymer solvent or hardening liquid. The size of the microencapsulated pharmaceutical increased as the core:coat ratio increased to a maximum of 1.5:1. There is an upper size limit of the pharmaceuticals which can be coated.