The formulation of a nasal nanoemulsion zaleplon in situ gel for the treatment of insomnia

Background: Zaleplon is a drug used for the treatment of insomnia and is available in tablet form; however, it has two major problems. First, the drug undergoes extensive first pass metabolism, resulting in only 30% bioavailability, and second, the drug has a poor aqueous solubility, which delays the onset of action. Objective: The objective of this study is to utilise nanotechnology to formulate zaleplon into a nasal in situ nanoemulsion gel (NEG) to provide a solution for the previously mentioned problems. Methods: The solubility of zaleplon in various oils, surfactants and co-surfactants was estimated. Pseudo-ternary phase diagrams were developed and various nanoennulsion (NE) formulations were prepared; these formulations were subjected to visual characterisation, thermodynamic stability study and droplet size and conductivity measurements. Carbopol 934 was used as an in situ gelling agent. The gel strength, pH, gelation time, in vitro release and ex vivo nasal permeation were determined. The pharmacokinetic study of the NEG was carried out in rabbits. Results: Stable NEs were successfully developed with a droplet size range of 35 to 73 nm. A NEG composed of 15% Miglyol, 30% Labrasol and 10% PEG 200 successfully provided the maximum in vitro and ex vivo permeation and enhanced the bioavailability in the rabbits by eightfold, when compared with the marketed tablets. Conclusion: The nasal NEG is a promising novel formula for zaleplon that has higher nasal tissue permeability and enhanced systemic bioavailability.