Comparative quality tests of two types of sustained release preparation of isosorbide dinitrate

Two commercial sustained release preparations of isosorbide dinitrate (ISDN), capsules (preparation A) and tablets (preparation B), were tested for content uniformity and dissolution pattern. The deviations in contents of the single doses from the declared content ranged from -7.7% to +9.7% which conformed to the standard (+/- 15%) of the Japanese Pharmacopeia X (JP X). Dissolution tests were performed using the rotating basket method described in JP X. The dissolution medium were No. 1 and 2 solutions (pH 1.2 and 6.8, respectively) specified in JP X disintegration test, and 0.05 M phosphate buffer solutions (pH 3.0 and 5.0). The dissolution patterns of both preparations were independent on the pH of the medium. However, there was a marked difference between the dissolution rates of the two: after 8 hr of the test, the rates of preparation A were 85-89%, but those of preparation B were only 42-50%. From preparation A a somewhat constant release of ISDN continued until the 6 hr. ISDN was determined by the HPLC method.