Which of the following is a requirement to ensure the physical stability of suspensions?

• A. Therapeutic Efficacy
• B. Physical Stability
• C. Esthetic Appeal
• D. Chemical Stability

Answer: (B)

Maintaining a uniform dispersion of particles over time is the key idea. In suspensions, physical stability means preventing sedimentation, creaming, aggregation, or irreversible flocculation so the suspension remains evenly dispersed and can be easily redispered after settling. To achieve this, the formulation must address the physical forces acting on the particles, using appropriate stabilizers, controlling particle size, and ensuring the system can be re-mixed without caking. Therapeutic efficacy relates to how well the drug works, esthetic appeal to appearance, and chemical stability to the chemical integrity of the drug—these are important, but they do not directly guarantee that the solid particles stay uniformly dispersed. Therefore, the requirement that directly ensures the physical stability of suspensions is maintaining physical stability itself.