Overview
Nucleoside analog for HSV/VZV. Requires viral thymidine kinase for activation. First-line for HSV encephalitis and neonatal HSV.
Dosing
HSV encephalitis: 10mg/kg IV q8h Genital HSV: 400mg PO TID Zoster: 800mg PO 5x/day Renal dosing: CrCl 25-50: Standard q12h CrCl 10-25: Standard q24h CrCl <10: 50% standard q24h HD: Dose after session
Pharmacokinetics
Onset: 1-2hr PO Peak: 1-2hr Duration: 4-8hr Metabolism: Minimal Elimination: Renal (62-91% unchanged) Half-life: 2-3hr
Pharmacodynamics
Mechanism: Inhibits viral DNA polymerase Spectrum: - HSV-1/2 - VZV Resistance: TK mutants
Clinical Considerations
Clinical Pearls: 1. First-line for HSV encephalitis 2. IV for serious infections 3. Hydrate well (nephrotoxicity risk) 4. Neurotoxicity in renal failure 5. Prophylaxis in transplant patients 6. Not for EBV/CMV 7. Start empirically in encephalitis 8. Monitor CrCl during therapy