Phase Sensitive Biodegradable Polymer Based In situ Implant of Olanzapine for Depot Injectable Formulation: In vitro Release and In vivo Absorption in Rats

Schizophrenia is a lifelong debeliating illness requiring extended treatment with antipsychotic agents. A novel atypical antipsychotic agent like olanzapine is required for a longer period of time to prevent relapses. Non-adherence to therapy is a very common and severe problem in these patients. Adherence to therapy can be improved by prescribing depot injectable formulations in such patients to significantly reduce the dosage frequency. PLGA based in situ gel implant was successfully developed on the principle of solvent exchange and evaluated for its in vitro release and in vivo performance in rats. The value of n of all formulations fell within the range of 0.51 to 0.83 which indicates the release pattern of Case II. The Cmax for formulation F2, F3 and F4 was 121.53, 81.64 and 54.39 ng/ml, respectively. Both in vitro release and in vivo pharmacokinetic data indicate that such formulations can be applied for at least one month sustained release with tolerable initial burst release. Olanzapine PLGA based in situ gel implant can be a potential candidate for depot injectable formulation intended to provide sufficient plasma levels for at least 30 days.