Preparation of a Progesterone Thermosensitive In Situ Gel Nano‐Emulsion Using an Organic Oil for Progesterone Delivery and In Vitro Release Study

ABSTRACT This study aims to formulate a thermosensitive in situ gel nano‐emulsion (NE) using a high‐energy method for delivering progesterone through the vagina. The components of the NE, namely sesame oil, Transcutol P, and Labrasol, were selected based on solubility and partial pseudoternary phase diagram studies. Poloxamer derivatives were added to the selected NE to optimize its gelling temperature. The prepared in situ gel NE had a mean droplet size of 26.44 ± 0.32 nm, a poly dispersity index (PDI) value of 0.35 ± 0.02, and desirable pH and viscosity. The encapsulation efficiency (EE%) of the prepared NE obtained 84.54%, which is consistent with scientific findings. In vitro release studies revealed that both the in situ gel NE and the control microemulsion exhibited sustained release. However, the in situ gel NE showed a slower release rate than the control sample. The in situ gel NE was stable during the heat‐cold cycle, freeze–thaw cycle, and centrifugation, as confirmed by visual evaluation, droplet size, and polydispersity index measurements. This study presents an optimized formulation with suitable physicochemical properties and a desirable release profile, making the in situ gel NE an effective novel delivery system for treating diseases related to the progesterone hormone.