Question

Which of the following flocculating agent is suitable for a negatively charged drug for preparation of suspension?

• A. \( \text{Aluminium chloride} \)
• B. \( \text{Acacia} \)
• C. \( \text{Tragacanth} \)
• D. \( \text{Sodium lauryl sulphate} \)

Hint:

Remember the rule of opposite charges: positively charged flocculating agents are used for negatively charged drugs, and vice versa, to neutralize surface charges and promote aggregation.

Answer 1

The Correct Option is A

Flocculating agents are used in suspensions to promote the formation of light, fluffy aggregates of the dispersed particles, which settle more rapidly but are easily redispersed with gentle shaking. For a negatively charged drug, a positively charged flocculating agent is generally required to reduce the repulsive forces between the particles and facilitate flocculation. Aluminium chloride is a trivalent salt that provides positively charged aluminium ions (\( \text{Al}^{3+} \)) in solution, making it suitable for flocculating negatively charged drug particles. Acacia and tragacanth are natural hydrocolloids that are typically used as suspending agents to increase the viscosity of the medium and prevent settling; they don't primarily act as charge neutralizers for flocculation. Sodium lauryl sulphate is an anionic surfactant and would likely increase the negative charge on the drug particles, thus hindering flocculation.