Evaluation of solid lipid microparticles produced by spray congealing for topical application of econazole nitrate

Objectives: The aims of this study were to evaluate the suitability of the spray congealing technique to produce solid lipid microparticles (SLMs) for topical administration and to study the skin permeation of a drug from SLMs compared with solid lipid nanoparticles (SLNs). Methods: Econazole nitrate was used as model drug and Precirol ATO 5 as the lipidic carrier. SLMs and SLNs were both prepared at 5 : 1, 10 : 1 and 12.5 : 1 lipid : drug weight ratios and characterised in terms of particle size, morphology, encapsulation efficiency and chemical analysis of the particle surface. SLMs and SLNs were also incorporated into HPMC K 100M hydrogels for ex-vivo drug permeation tests using porcine epidermis. Key findings: SLMs had particle sizes of 18-45 μm, while SLNs showed a mean diameter of 130-270 nm. The encapsulation efficiency was 80-100%. Permeation profiles of econazole nitrate were influenced by both particle size (significant difference until 9 h) and the amount of lipid. Conclusions: The results confirm the usefulness of SLNs as carriers for topical administration and suggest the potential of SLMs for the delivery of drugs to the skin.