Cidofovir is used for treatment of CMV retinitis and severe molluscum contagiosum in HIV/AIDS patients. Its mechanism of action is:
- A Thymidine kinase-dependent phosphorylation to active triphosphate
- B Direct inhibition of viral DNA polymerase without requiring viral kinase activation ✓
- C Inhibition of viral capsid assembly
- D Blockade of viral integrase
Correct answer: B. Direct inhibition of viral DNA polymerase without requiring viral kinase activation
Explanation
Cidofovir is a nucleotide analogue (acyclic phosphonate) that does not require viral thymidine kinase for activation — unlike acyclovir which requires VZV/HSV thymidine kinase. Cidofovir is phosphorylated by cellular kinases to cidofovir diphosphate, which directly inhibits viral DNA polymerase with competitive inhibition. This is why cidofovir retains activity against acyclovir-resistant herpes strains (TK-deficient mutants). Major adverse effect is dose-limiting nephrotoxicity (requires probenecid and IV hydration pre-medication).
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.