Three different products containing 240 mg of verapamil hydrochloride in a coated tablet with sustained release were compared using the blinded dissolution test. The amount of the active substance released from the tablet and its dynamics differed significantly with all three products after 3 hours of dissolution. With product C (Isoptin SR, a proprietary product manufactured by Knoll), 92,2 % of the active substance was released after seven hours. With generic products A and B, the amounts were higher and lower, respectively. The dynamics of release of the active substance was linear only with the proprietary product. Irregular and non-linear rates of active substance release from the tablet may result in clinically suboptimal efficacy and safety of generic products.

        Key words: dissolution test – verapamil – sustained release – UV spectrophotometry