Which topical Anti Herpes Agent has the worst toxic SPK side effect associated with it?

Which topical Anti Herpes Agent has the worst toxic SPK side effect associated with it?

• A. Trifluridine
• B. Ganciclovir
• C. Acyclovir
• D. Penciclovir

Answer: (A)

The main idea here is that the eye’s surface toxicity varies among topical antiherpetic drugs, and one agent is notably more damaging to the corneal epithelium than the others. Trifluridine tends to cause the most corneal surface toxicity, presenting as superficial punctate keratitis. Why this is the best answer: Trifluridine is a nucleoside analogue that becomes activated by many cellular kinases and can disrupt DNA synthesis in both infected and uninfected corneal epithelial cells. Its lack of strong selectivity for viral enzymes means it damages the healthy corneal surface more readily, leading to pronounced SPK and irritation. In contrast, ganciclovir and penciclovir are activated more selectively by viral kinases, so they spare uninfected epithelial cells to a greater extent and produce milder surface toxicity. Acyclovir shares a similar pattern with relatively better tolerability. Because of its higher risk of ocular surface damage, trifluridine is generally used for shorter periods, with close monitoring and consideration of switching to a less toxic option if SPK develops. So the agent with the worst SPK side effect is trifluridine.

The main idea here is that the eye’s surface toxicity varies among topical antiherpetic drugs, and one agent is notably more damaging to the corneal epithelium than the others. Trifluridine tends to cause the most corneal surface toxicity, presenting as superficial punctate keratitis.

Why this is the best answer: Trifluridine is a nucleoside analogue that becomes activated by many cellular kinases and can disrupt DNA synthesis in both infected and uninfected corneal epithelial cells. Its lack of strong selectivity for viral enzymes means it damages the healthy corneal surface more readily, leading to pronounced SPK and irritation. In contrast, ganciclovir and penciclovir are activated more selectively by viral kinases, so they spare uninfected epithelial cells to a greater extent and produce milder surface toxicity. Acyclovir shares a similar pattern with relatively better tolerability. Because of its higher risk of ocular surface damage, trifluridine is generally used for shorter periods, with close monitoring and consideration of switching to a less toxic option if SPK develops.

So the agent with the worst SPK side effect is trifluridine.