Development and Evaluation of Self Micro-Emulsifying Formulation of Venlafaxine HCl with Improved Antidepressant Activity

Abstract:

Aim/Background: Venlafaxine HCl (VEN) is an antidepressant drug with extensive first pass metabolism and low oral bioavailability. In the present study, a solid self-emulsifying formulation of Venlafaxine was developed and evaluated for in vitro and in vivo performance. Materials and Methods: Various oils, surfactants, and cosurfactants were screened for the solubility of Venlafaxine in them. Surfactants were further screened based on their ability to emulsify oils. For the SMEDDS formulation, Caprol PGE 860 was selected as oil base, Tween 20 as a surfactant and propylene glycol as a co-surfactant. Pseudoternary phase diagrams were plotted with different concentrations of these three components with water to identify microemulsion area. The optimized formulation containing Venlafaxine (5.9%), Caprol PEG 860 (9.3%), Tween 20 (42.4%) and propylene glycol (42.4%) was converted into solid SMEDDS (S-SMEDDS) by using Spray Drying method and evaluated for the flow property, drug content, drug release, DSC, XRD, SEM and in vivo antidepressant activity. Results: The optimized SMEDDS formulation demonstrated globule size of 21 nm with no signs of precipitation upon dilution, was thermodynamically stable, and released more than 90% of Venlafaxine in 30 min. S-SMEDDS formulation was free flowing and SEM and PXRD studies revealed amorphous state of S-SMEDDS. In vivo antidepressant activity by forced swim test and anti-anxiety test by EPM maze test in rats demonstrated significant efficacy of SMEDDS formulation over plain drug. Conclusion: A self-emulsifying formulation of Venlafaxine was successfully developed and showed improved antidepressant activity in comparison to pure drug, thus can serve as potential alternative to existing oral formulations.

Keywords: Venlafaxine, Self-microemulsifying drug delivery system, Anti-depressant, First pass effect, Bioavailability, Solubility.