Fortified topical antibiotics are high-concentration preparations used to achieve bactericidal levels in the cornea and anterior chamber for sight-threatening infections. The most commonly used fortified agent is tobramycin, prepared at a high dose (often around 14 mg/mL) to maximize coverage against gram-negative bacteria, including Pseudomonas. It’s typically used in combination with another antibiotic (such as cefazolin) to provide broad-spectrum coverage, especially for severe keratitis or endophthalmitis. So, the fortified agent described here is tobramycin. Cefazolin alone provides gram-positive coverage but is not the fortified agent by itself; vancomycin and gentamicin can be used in fortifications in certain scenarios, but tobramycin is the standard first choice for sight-threatening cases.

Donepezil lowers intraocular pressure by increasing acetylcholine in the eye. By inhibiting acetylcholinesterase, it boosts parasympathetic activity, and the extra acetylcholine stimulates muscarinic receptors on the ciliary muscle. This causes the ciliary muscle to contract, opening the trabecular meshwork and enhancing aqueous humor outflow, which reduces IOP. The other drugs listed lower IOP through their own glaucoma-specific mechanisms (prostaglandin-mediated outflow, alpha-adrenergic–mediated outflow plus reduced production, or beta-blocker–mediated production reduction), but the question highlights donepezil as the agent capable of SAMPLEdecreasing IOP through cholinergic stimulation.

Pupil dilation and increased intraocular pressure can be triggered by systemic sympathetic stimulation from certain OTC decongestants. Pseudoephedrine is a common example that activates alpha-adrenergic receptors, providing decongestion but also potentially dilating the pupil. In eyes with high intraocular pressure or narrow angles, this dilation can worsen outflow obstruction and raise IOP, leading to blurred vision and even diplopia in susceptible individuals. The other options lack this decongestant mechanism or don’t have the same risk of raising IOP; for instance, anticholinergic medicines like diphenhydramine can cause blurred vision through accommodation effects, but they’re not decongestants, and acetaminophen and ibuprofen don’t typically affect vision or IOP.

The key idea is that fortified topical therapy for eye infections relies on fluoroquinolones with broad spectrum and strong tissue penetration, so later generations are favored. Third- and fourth-generation fluoroquinolones have enhanced activity against a wide range of organisms, including Gram-positive bacteria such as Staphylococcus aureus (and some MRSA) as well as excellent Pseudomonas coverage, and they achieve good corneal and intraocular penetration. This makes them well suited for high-concentration, fortified formulations used in serious ocular infections like keratitis and endophthalmitis. Examples include levofloxacin (3rd generation) and the 4th-generation agents like moxifloxacin and gatifloxacin. While earlier generations can cover Pseudomonas, they have relatively less Gram-positive activity and are less favorable for fortified regimens, so the 3rd/4th generations are the best fit for fortified topical therapy.