Development and optimization of mirtazapine loaded lipid-based transethosomal gel; in-vitro, ex-vivo and toxicological analysis

Background: Application of drugs through the transdermal route is preferable over other routes of drug delivery because of the ease of drug administration and reduced systemic side effects. Mirtazapine is a BCS class II noradrenergic and specific serotonergic drug and shows poor solubility and bioavailability. Objective: This study aims to develop and optimize a mirtazapine-loaded lipid-based transethosomal gel to enhance transdermal drug delivery and bypass first-pass metabolism. The current study is an attempt to minimize the systemic side effects associated with oral administration of mirtazapine and to avoid first pass metabolism by administering the drug through the skin. Methods: Transethosomes were formulated using the cold method and optimized via Box–Behnken design by varying phospholipid, surfactant, and ethanol concentrations. Results: The optimized formulation (F-16) exhibited high entrapment efficiency (75.92%) and cumulative drug permeation (73.62%) after 6 hours. Multiple characterization tests confirmed nano-sized, stable vesicles with a zeta potential of ?34.1 mV and particle size of 479.3 nm. The transethosomal dispersion was incorporated into a Carbopol gel and evaluated for pH, viscosity, spreadability, drug content, and skin permeation. Ex-vivo studies showed enhanced skin permeation from the gel compared to the dispersion. Stability tests confirmed physical integrity over 60 days, while skin irritation and toxicological studies in animal models indicated excellent biocompatibility, with no signs of inflammation or organ toxicity. Conclusion: These findings and the study suggests that the transethosomal gel formulation is a promising and safe approach for transdermal delivery of mirtazapine, potentially improving its bioavailability and therapeutic effectiveness resulting in bypassing first pass metabolism.