A common description of suspending agents is that they...

• A. Are added to thicken the dispersion medium to avoid rapid settling
• B. Are added to increase the rate of drug dissolution
• C. Do not affect the physical stability of suspensions
• D. Are used to remove water from the formulation

Answer: (A)

Suspending agents are used to slow down the settling of solid particles in a suspension by thickening the liquid phase. When the dispersion medium is more viscous, the rate at which particles fall under gravity decreases, as described by Stokes’ law, which shows that settling velocity is inversely related to viscosity. This helps keep particles dispersed longer and makes the suspension easier to redisperse after it has stood. In addition, these agents often improve wetting of particles and can form a network that stabilizes the suspension, further reducing aggregation and sedimentation. They are not primarily meant to remove water or to boost dissolution of the drug, which is governed by solubility and diffusion rather than the viscosity of the medium.