INVESTIGATION OF DISSOLUTION PROFILES FROM SUSPENSIONS CONTAINING BENZOYL METRONIDAZOLE USING A STATISTICAL-MODEL WITH REPEATED MEASUREMENTS

The Mexican Pharmacopeia (MP) dissolution general test was carried out on one and two lots of suspensions from each one of three commercial drug products, containing benzoyl metronidazole, and using water or 0. 1 N hydrochloric acid as dissolution medium. When we used paddles at 1 00 rpm,and water as dissolution medium, 72 to 99% of the active substa nce was dissolved after 60 minutes, showing differences between the di ssolution profiles from these drug products. When testing conditions w ere changed to 0.1 N hydrochloric acid at 75 r. p. m., the amount diss olved of active substance varied from 25 to 100%, showing different di ssolution rate profiles for all 6 drug products. The ANOVA for the sta tistical model with repeated measurements was applied to the observed dissolution rate data, showing no parallel behaviour between each diss olution profile. Using the ANOVA for nested models, and the hydrochlor ic acid data to investigate the dissolution efficiency, we found intra class difference but no interclass difference. In contrast, by using t he per cent dissolved with the same dissolution medium data, we found significant differences between drug products, but not between lots. S ignificant difference was observed between drug products, when using w ater as dissolution medium, either when using the dissolution efficien cy data or the per cent dissolved in 60 minutes. The data suggests tha t pharmaceutical suspensions have the same problems with the deaggrega tion rate such as tablets and capsules do, therefore, it is important to extend the dissolution testing for suspensions with a poor water so lubility.