By use of a spectrophotometric method the quantity of binding of medicinal compound [succinate of 2,5-dimethyl-4-benzoyl-oxypiperidine (AK-29)], over gels of polyacrylic acid, and liberation of medicinal compound (MC) from the gel phase were investigated. It was established that both concentration and pH dependency of AK-29 sorption over PAA gels pass through a maximum and increase with increasing degree of gel crosslinking. The yield of MC from the gel phase, depending on the conditions, reaches 80% and accelerates at the change of the aqueous phase to a physiological one. (c) 2005 Wiley Periodicals, Inc.