What is an example of a water-soluble base?

• A. Aquaphilic
• B. Lanolin ointment
• C. Petrolatum ointment
• D. Polyethylene glycol ointment

Answer: (D)

Water-soluble bases are hydrophilic and can mix with water, meaning they are washable and often used when a non-greasy, water-washable ointment is desired. These bases are typically based on polyethylene glycols (PEG), which are inherently water-loving and dissolve or disperse in water, allowing incorporation of aqueous solutions and hydrophilic drugs.

Polyethylene glycol ointment is the example that fits this description because the PEG polymers make the base water-soluble and water-miscible. In contrast, petrolatum ointment and lanolin ointment are oil-based (oleaginous) bases that are hydrophobic and not easily washed off with water. The term aquaphilic isn’t a standard designation for a true water-soluble base, so it doesn’t represent the proper water-soluble category.