FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam

Which agent is commonly added to suspensions to increase viscosity?

1. Glycerin

2. Acetic acid

3. Hydroxymethyl cellulose

4. Carbonates

The correct answer is: Hydroxymethyl cellulose

Hydroxymethyl cellulose is commonly added to suspensions to increase viscosity due to its ability to form a gel-like structure in solution. This property allows it to stabilize the suspension, preventing the solid particles from settling at the bottom, thereby improving the overall consistency and performance of the formulation. By increasing viscosity, hydroxymethyl cellulose can also enhance the texture and mouthfeel of liquid medications, making them more palatable for patients. In contrast, glycerin can act as a humectant and solvent but does not primarily function as a viscosity-increasing agent. Acetic acid is predominantly used as a pH adjuster rather than a thickener. Carbonates typically do not contribute to increased viscosity and are more commonly associated with effervescent formulations or acting as buffering agents. Thus, hydroxymethyl cellulose stands out as the most effective choice for enhancing viscosity in suspensions.