What is the primary purpose of including a surfactant in a topical formulation?

• A. Reduce surface tension
• B. Increase viscosity
• C. Decrease pH
• D. Increase drug potency

Answer: (A)

In topical formulations, surfactants primarily act to reduce surface tension at interfaces, which improves wetting and spreading on the skin. Their amphiphilic nature (having both hydrophilic and lipophilic parts) lets them position themselves at the air–skin or oil–water interfaces, lowering the energy needed for the liquid to spread over the skin’s surface. This enhanced wetting leads to more uniform coverage, better initial release of the active drug from the vehicle, and can aid in solubilizing lipophilic drugs through micelle formation.

Increasing viscosity would make spreading harder, decreasing pH is not the general role of a surfactant, and increasing drug potency isn’t a direct or primary effect of including a surfactant.