Stability of Venlafaxine Immediate-Release Suspensions

Abstract Venlafaxine is a novel antidepressant that works by inhibiting the reuptake of serotonin and norepinephrine. The objectives of this study were to reformulate a venlafaxine extended-release suspension into an immediate-release preparation and then determine the physical and chemical stability of the new venlafaxine formulation. Suspensions of venlafaxine (75mg/5mL) were prepared from extended-release microspheres that had been reduced to powder and then dispersed in either OraPlus/OraSweet (50:50) or simple syrup. Triplicate samples of the suspensions were collected from amber plastic bottles stored at either 5 degrees C or 23 degrees C on days 0, 7, 14, 21, and 28, and assayed. Physical stability was based on color and pH changes. A validated high performance liquid chromatography assay method was used to determine the chemical stability of the active ingredient. This study found that venlafaxine immediate-release suspensions, prepared in either OraPlus/OraSeet or simple syrup, are physically and chemically stable for 28 days when stored in amber plastic bottles at either 5 deg C or 23 deg C.