Which of the following is NOT a wetting agent commonly used in compounding?

In the context of compounding, wetting agents are substances that help to reduce the surface tension of a liquid, allowing it to spread more easily over a solid surface or to mix with other liquids. Alcohol, glycerin, and propylene glycol are all known for their wetting properties. They effectively facilitate the dissolution of powders in liquids and enhance the overall homogeneity of mixtures.

Polyethylene glycol (PEG), while it can be used as a solvent and vehicle in compounding, is not primarily classified as a wetting agent. PEG is more commonly recognized for its role in modifying the viscosity of formulations and its use as a base in ointments and creams. Therefore, while it may have some wetting properties, it does not function primarily as a wetting agent compared to the others listed. Understanding these distinctions helps in selecting the appropriate agents for specific compounding purposes.