Which option lists bases commonly used in ophthalmic ointments?

• A. Water-based gels only
• B. Pure mineral oil
• C. A mixture of white petrolatum and liquid petrolatum; lanolin; a mix of PEG and mineral oil
• D. Glycerin-only solutions

Answer: (C)

In ophthalmic ointments you want a semi-solid, occlusive base that stays on the surface of the eye and provides stable drug release. The classic bases are petrolatum-based mixtures and related emollients, which create a thick, lipophilic matrix that resists quick washout by tears. A combination of white petrolatum and liquid petrolatum gives the right range of firmness and oil content. Adding lanolin adds emulsifying and emollient properties, improving texture and drug dispersion. A PEG/mineral oil blend lets formulators tweak the hydrophilic–lipophilic balance and viscosity for the specific drug and desired release profile. Water-based gels or glycerin-only solutions wouldn’t remain on the ocular surface as ointment bases, and pure mineral oil is too fluid to provide the necessary occlusion. Together, these ingredients form the typical, effective ophthalmic ointment bases.