Which statement best describes the difference between ophthalmic solutions and ointments in terms of corneal penetration and residence time?

• A. Solutions provide rapid onset with quicker clearance; ointments provide extended residence time and drug exposure but may cause blurred vision.
• B. Ointments provide rapid onset with quicker clearance; solutions provide extended residence time and blurred vision.
• C. Solutions have longer residence time and slower clearance than ointments.
• D. Ointments and solutions have identical penetration and residence times.

Answer: (A)

The key idea is how dosage form affects how long the drug stays on the eye and how quickly it gets into the cornea. Solutions are thin and wash out quickly because the tear film and blinking rapidly remove them, so they reach the cornea fast (rapid onset) but don’t stay long (quick clearance). Ointments are thick and form a film on the ocular surface, trapping drug and creating a reservoir that keeps it in contact longer, increasing the total exposure of the eye to the drug. That longer residence time comes with a trade-off: the ointment layer can blur vision. So the statement matching this reality—solutions give rapid onset with quicker clearance, while ointments provide extended residence time and drug exposure with possible blurred vision—best describes the difference.