The invention relates to a microcapsule of venlafaxine, a pharmaceutically acceptable salt of venlafaxine, an active metabolite of venlafaxine, a pharmaceutically acceptable salt of an active metabolite of venlafaxine, or combinations thereof, a pharmaceutical composition comprising the microcapsules and its method of preparation. The microcapsule comprises venlafaxine, a pharmaceutically acceptable salt of venlafaxine, an active metabolite of venlafaxine, a pharmaceutically acceptable salt of an active metabolite of venlafaxine, or combinations thereof, an alginate salt, a divalent cation vector and a mucoadhesive agent. The composition is intended for control release of the active ingredients over a period of time.