Formulations tramadol sustained release with an efficiency of 24 hours.

Solid dosage formulation comprising: a core comprising an active pharmaceutical ingredient (API) and a matrix and a coating comprising a physical mixture of polyvinyl acetate and polyvinylpyrrolidone and an active pharmaceutical ingredient, wherein the active pharmaceutical ingredient and core matrix are associated so that release of the pharmaceutical ingredient from the matrix of the core is controlled, so that release from the formulation of the active ingredient provided in the core is slower than the release of the active pharmaceutical ingredient disposed in the matrix coating, wherein the active pharmaceutical ingredient of the core and coating is the same and is tramadol or a stereoisomer or pharmaceutically acceptable salt thereof.