Foscarnet differs from ganciclovir in its activation requirements. This difference makes foscarnet the preferred agent in which situation?

• A Congenital CMV infection in a neonate
• B First-line treatment of CMV esophagitis in a newly diagnosed AIDS patient
• C Prophylaxis of CMV disease after renal transplantation
• D CMV retinitis in a patient with severe neutropenia from prior ganciclovir exposure ✓

Explanation

Foscarnet is a pyrophosphate analog that directly inhibits viral DNA polymerase and needs no phosphorylation by viral kinases, so it retains activity against ganciclovir-resistant strains with UL97 kinase mutations. Unlike ganciclovir it does not cause myelosuppression, making it the choice when marrow reserve is poor. Its dose-limiting toxicity is nephrotoxicity with electrolyte wasting.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.