Cyclosporine Dissolution Test from a Lipid Dosage Form: Next Step Towards the Establishment of Release Method for Solid Lipid Microparticles

<b>Background:</b> The release study is a standard tool for the development, evaluation, and control of dosage forms. In the case of traditional drug delivery systems, it is conducted in accordance with the established principles available in the European and American Pharmacopoeias or guidelines proposed by registration agencies. The problem is the study of modern carriers, not yet described in compendia, which require adjustments to traditionally used methods. <b>Objectives:</b> The present study focuses on developing an optimal method for testing the release of cyclosporine (Cs, 0.5-4%) incorporated in solid lipid microparticles (SLM) dispersions (10%) intended for administration in the form of eye drops. This is a multicompartment lipid carrier that provides prolonged release of the active substance. <b>Methods:</b> Three methods of testing the release were compared: the dialysis bag method, the horizontal cells technique, and a method without a membrane. <b>Results:</b> During the analyses, the proper membrane was selected and the effect of the lysozyme enzyme on the release profile was analyzed. The effect of the composition of the acceptor fluid on the obtained results was also assessed. In the model without a membrane, up to 60% of the Cs was released within 30 min due to the <i>burst effect</i>. In horizontal chambers, no formulation released more than 14% of the Cs over 96 h, while at the same time, 60-70% of the Cs was released from the dialysis bag. <b>Conclusions:</b> Based on the obtained results, the dialysis bag method was selected to study the release of Cs from SLM without the need to use multicomponent artificial tear fluid as an acceptor medium.