Regulation of the tetracycline hydrochloride release from polyacrylate microspheres. Part 1.

Due to the precipitation of free bases sparingly soluble in water, it is not possible to achieve a uniform release in the gastrointestinal tract of delayed action drugs containing salts of weak bases, e.g. tetracycline hydrochloride, at pH-values surpassing their pKa values. The problem of drug release control can be solved by adding Eudragit L to the polymetacrylate (Eudragit RS) microspheres. It has been established that 30% Eudragit L ensures a gradual uniform release of tetracycline hydrochloride (KOr = 11%/h) irrespective of variations in the pH of the gastrointestinal tract.