Formulation, characterization and statistical optimization of enalapril-loaded lipospheres

Lipid-based polymers have been proved efficient drug carriers for overcoming the insufficiencies of conventional formulations. Ceresin wax was employed to improve permeability, oral bioavailability and patient compliance by preparing enalapril (EP)-loaded lipospheres with a simple solvent evaporation method. A Box–Behnken design with the proposed polynomial equations and quadratic model was applied to investigate and statistically validate the collective influence of formulation variables on lipospheres. Spherical smooth-surfaced lipospheres with an average size of 55 μm with excellent micromeritic properties were produced. Differential scanning calorimetry, X-ray diffraction and Fourier transmission infrared spectroscopy findings proved the lack of any possible interaction between formulation components. The zeta potential ranged from −5 to −20 mV, suggesting the significant stability of lipospheres. Responses such as percentage yield (29–68%), entrapment efficiency (21–53%) and drug release (42–93%) were found to be affected greatly by the concentrations of lipids and the surfactant, and the stirring speed. Reduced and sustained EP release from lipospheres may lower treatment cost and enhance hypertensive patients’ compliance.