Acyclovir vs Ganciclovir and foscarnet
How to tell Acyclovir and Ganciclovir and foscarnet apart when a board question makes them look alike.
Acyclovir is HSV/VZV plus viral TK; ganciclovir is CMV plus marrow; foscarnet is resistant CMV/HSV plus renal-electrolyte toxicity.
Side by side
HSV/VZV drug activated by viral thymidine kinase, with crystalline nephropathy and neurotoxicity clues.
CMV/resistant herpesvirus lane: ganciclovir causes marrow suppression; foscarnet causes renal and electrolyte toxicity.
Acyclovir is phosphorylated by viral thymidine kinase and inhibits viral DNA polymerase.
Ganciclovir targets viral DNA polymerase after phosphorylation; foscarnet directly inhibits viral DNA polymerase as a pyrophosphate analog.
HSV encephalitis, genital herpes, VZV, or thymidine-kinase activation points acyclovir.
CMV retinitis/transplant CMV plus neutropenia points ganciclovir; resistant CMV/HSV plus electrolyte derangements points foscarnet.
The trap
Nephrotoxicity alone is not enough, because acyclovir and foscarnet can both injure kidneys.
The repair move
For herpesvirus antivirals, first name the virus, then the activation requirement, then the limiting toxicity.
Try a free question
CoreA patient with HSV encephalitis receives an antiviral that requires viral thymidine kinase activation and can cause crystalline nephropathy if hydration is poor. Which drug is this?
Show answer and explanation
Answer: A. Acyclovir. Acyclovir is activated by viral thymidine kinase and targets viral DNA polymerase; nephrotoxicity is the key toxicity clue.
Why the other choices are tempting
- B. Ganciclovir is CMV-focused and remembered for bone marrow suppression.
- C. Foscarnet directly inhibits viral DNA polymerase without activation and causes nephrotoxicity/electrolyte problems.
- D. Oseltamivir is an influenza neuraminidase inhibitor.
- E. Ribavirin is a nucleoside analog remembered for hemolytic anemia and teratogenicity.
Flashcards
Tap a card to flip it.
What is the fastest separator for Acyclovir vs Ganciclovir and foscarnet?
Acyclovir is HSV/VZV plus viral TK; ganciclovir is CMV plus marrow; foscarnet is resistant CMV/HSV plus renal-electrolyte toxicity.
What clue should make you choose Acyclovir?
HSV/VZV drug activated by viral thymidine kinase, with crystalline nephropathy and neurotoxicity clues.
Quick answers
What is the fastest way to tell Acyclovir from Ganciclovir and foscarnet?
Acyclovir is HSV/VZV plus viral TK; ganciclovir is CMV plus marrow; foscarnet is resistant CMV/HSV plus renal-electrolyte toxicity.
What is the key clue for Acyclovir?
HSV/VZV drug activated by viral thymidine kinase, with crystalline nephropathy and neurotoxicity clues.
What is the key clue for Ganciclovir and foscarnet?
CMV/resistant herpesvirus lane: ganciclovir causes marrow suppression; foscarnet causes renal and electrolyte toxicity.
What is the common trap with Acyclovir vs Ganciclovir and foscarnet?
Nephrotoxicity alone is not enough, because acyclovir and foscarnet can both injure kidneys.