Dissolution profiles (DPs) of Dichlotride tablet containing hydrochlorothiazide, supplied by Merck Sharp & Dohme, N. J., U.S.A. and
used as the reference formulation in this study, were compared with those obtained from sixteen commercial tablets. Dissolution tests were
performed by employing a USP XXIII apparatus-I (Basket type) at 100 rpm. Pure water, 0.1N HCl and pH 7.4 buffer were used as the
studied media. Released percentages of the active ingredient were measured at 10, 20, 30, 45, 60 and 90 minutes, respectively. The factor
f2 of the FDA’s SUPAC Guide was applied to the qualitative determination of ‘similarity’ between pairs of dissolution profiles of
Dichlotride and those of each investigated formulations. Results indicated that 5 out of 16 tested samples (ca. 31.3%) were suited to
Dichlotride in all of three media. In addition, three other samples (ca. 18.8% each) were similar to Dichlotride in both water and 0.1N HCl.
Two tested formulations gave similar in-vitro release profiles to those of Dichlotride only in corresponding pure water or the pH 7.4 buffer
solution (ca. 6.3% each), in other words, different in both of the other two media. The last six samples showed completely different profiles
compared with that of Dichlotride no matter what medium was used. In summary, the number of tested samples showing similar DPs
as Dichlotride in individual media were as follows: 8 in water (50%); 9 in 0.1N HCl (ca. 56.3%); and 6 in pH 7.4 buffer solution (37.5%).