Fig. 1

Dissolution profiles of two references and five generic diclofenac tablet brands available on the Saudi market. Mean (SD) amount of drug released at the specified times are shown on the left axis (continuous line) and percent of label amount released on the right axis (interrupted line). United States Pharmacopoeia (USP) dissolution apparatus type II (paddle apparatus) was used with a stirring rate of 50 ± 1 rpm (except for “infinity” time) and a temperature of 37 ± 0.5 ºC. Brands’ label details are available in Additional file 1, Label information. a 50 mg immediate-release diclofenac potassium tablet brands. R1, reference brand; G1–G4, generic brands. Dissolution medium was phosphate buffer (pH 6.8). Time 105 min indicates amount released with a stirring rate of 250 rpm for 15 min (“infinity”). b 100 mg sustained-release tablet brands. R2, reference brand; G5, generic brand. The insert shows the acceptable range of amount released at specified times according to USP test-1 and test-2 together with the amount released by R2 and G5. Time 0 min indicates amount released after 120 min in 0.1 N HCl. Other times indicate amount released in phosphate buffer (pH 7.5). Time 25 h indicates amount released with a stirring rate of 250 rpm for 1 h (“infinity”)