Abstract

Paulo Henrique Pires de Aguiar

This study reports the differences in physical and chemical stability of suspension with dissolved and non dissolved main active compound. In the first case it is methenamine and the other one is anesthesin. At the same time we analyzed two fresh and two 18-months old formulations of both magistral preparations. Anesthesin suspensions did not show any significant physical or chemical changes in 18 months except changes in appearance. On the other hand suspension with methenamine showed as very unstable system. Methenamine was hydrolyzed in water and ammonia and formaldehyde were determined as degradation products. Level of methenamine in preparations after 18 months was 84.6 ± 1.1%. Also the value of water was slightly decreased in old formulation with methanamine, which indicates a physical unstable system.