Nevirapine loaded Poloxamer 407/Pluronic P123 mixed micelles: Optimization of formulation and in vitro evaluation.

An attempt has been made to develop polymeric mixed micelle delivery system using Poloxamer 407 and Pluronic P123 for the encapsulation of an antiretroviral drug, Nevirapine. The stability of formulated mixed micellar system at different ratios (1:2, 1:1 and 2:1) and standard thermodynamic parameters of micellization have been determined from the temperature dependence of the critical micelle concentration. The process of micellization of Poloxamer 407/Pluronic P 123 system has been found to be entropy dominant at low temperatures and enthalpy driven at high temperatures. The amity of the different components of mixed micelles has been explored using Fourier transform infrared spectroscopy, Differential scanning calorimeter and X-ray diffraction studies, which rule out the possibility of any interactions between the drug and excipients. Micropolarity measurements infer that the drug is solubilized in the inner core of mixed micelles. In addition, dialysis method has been employed to determine the entrapment efficiency of all the three formulations. The formulation at 1:1 ratio exhibits high entrapment efficiency along with sustained release of the drug.