FIELD: medicine, pharmacy. SUBSTANCE: invention relates to tablets for oral use and provides the sustained-release an active substance. Agent has the moisture-nonsensitive pharmaceutically acceptable tramadol salt as an active substance taken at amount 10-85 wt.-%. Agent has also usual for tabletted form accessory additions and as a pharmaceutically acceptable matrix forming agent - at least one ether and/or ester of cellulose at amount 10-40 wt. -% at viscosity 3 000-150 000 MP ads at 20 C in 2 wt.-% an aqueous solution. New drug releases tramadol salt independently on pH value of an environment, type and amount of filling agent. At given mass and form of tablet the pattern of release of tramadol salt does not depend on the content of biologically active substance and amount of matrix forming agent. EFFECT: improved quality of the drug. 5 cl, 3 dwg, 8 ex
