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Case 2: Acyclovir-Resistant Herpes Simplex Virus Infection

You answered:

D Valacyclovir (Valtrex) 1000 mg PO tid.

This answer is incorrect. Valacyclovir (Valtrex) is an acyclovir prodrug (it is the L-valine ester of acyclovir). Following absorption of valacyclovir, it is almost completely converted to acyclovir during first-pass hydrolysis in the liver and intestines. Although oral valacyclovir has a relative bioavailability 3 to 5 times greater than acyclovir (and oral doses can generate relatively high serum levels of acyclovir), it would not likely override the acyclovir resistance.

A Acyclovir (Zovirax) 10 mg/kg IV q8h.
B Famciclovir (Famvir) 500 mg PO tid.
C Foscarnet (Foscavir) 40 mg/kg IV q8h.


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