Development and Characterization of an In Vitro Release Assay for Liposomal Ciprofloxacin for Inhalation

A novel method was developed and optimized to measure the in vitro release (IVR) of two liposomal ciprofloxacin formulations under development to treat lung infection. The release agent, bovine serum, has components that interact with liposomes to cause the encapsulated drug to be released. The precision and accuracy of the method were characterized. The method has a nearly linear release phase initially, which then approaches a plateau value after 2-4 h. The robustness of the method was verified over a range of release agent and liposomal concentrations, and in response to changes in incubation temperature, buffer pH, and storage containers of serum. For this sample and separate IVR method, there is less than 2% release at the T = 0 time point, indicating negligible artifactual release before analysis. For both inhaled liposomal ciprofloxacin products, the plateau value represents 100% release of the encapsulated drug. The key elements of this IVR method may prove useful for characterization of other liposomal products as well. (c) 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:314-327, 2014