Which of the following is NOT an example of a viscosity inducing agent commercially available?

• A. Cellulose
• B. Carboxymethylcellulose
• C. Starch
• D. Xanthan Gum

Answer: (A)

Viscosity-inducing agents are substances that increase the thickness of a formulation by dissolving, swelling, or forming gels in the liquid. The soluble cellulose derivative, carboxymethylcellulose, is a classic thickener used to raise viscosity in suspensions and gels. Starch thickens by gelatinizing when heated or dispersed, creating a more viscous mixture. Xanthan gum is a highly efficient thickener that provides viscosity even at low concentrations and in a wide pH range.

Native cellulose, however, is insoluble in water and does not form a viscous solution in typical aqueous pharmaceutical media. It’s mainly used as a filler/diluent in solid dosage forms rather than as a viscosity modifier in liquids. Because of this, native cellulose is not an example of a commercially available viscosity-inducing agent.