A Comparative Evaluation of Five Common Suspending Agents Used in Drug Safety Studies

Abstract

Suspensions of three drugs at three concentrations (0.1, 1.0 and 10.0% w/w), prepared using five common suspending agents, have been evaluated for their suitability in drug safety studies. The suspending agents (methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose and gum tragacanth) were used in gels of similar viscosity. Sodium carboxymethylcellulose and hydroxyethylcellulose proved to be unsatisfactory in that drug assays for six of the nine suspension samples were outside the demanding limits set (±5% of theoretical). Methyl cellulose and hydroxypropylmethylcellulose were both considered to be equally satisfactory as the agent of first choice. Gum tragacanth performed slightly less well with the cationic drug used than the cellulose based agents. It is concluded that suspending agent gels should be of adequate viscosity to obtain satisfactory suspensions and that anionic suspending agents with the potential to interact with drugs are best avoided.