Acyclovir

Background

• Acyclic guanosine analog that competes with deoxyguanosine triphosphate to inhibit viral DNA polymerase
• Resistance mediated by mutation in or decrease of thymidine kinase
• Good penetration into CNS and vitreous if administered intravenously, though not orally1

Dosing

• Usual dose:
  • 5-10 mg/kg ideal body weight IV q8h
  • 200-400 mg PO 5 times daily
  • 800 mg PO 5 times daily (high dose)
• Herpes encephalitis: 10 mg/kg ideal body weight IV q8h

Renal Adjustment

• Oral
  • CrCl 30-49: usual dose
  • CrCl 10-29: usual dose
  • CrCl <10: usual dose q12h
  • Intermittent dialysis: 50% of usual dose q24h, given after dialysis on dialysis days
  • Continuous dialysis: usual dose
• Intravenous
  • CrCl 30-49: usual dose q12h
  • CrCl 10-29: usual dose q24h
  • CrCl <10: 50% of dose q24h
  • Intermittent dialysis: 50% of usual dose q24h, given after dialysis on dialysis days
  • Continuous dialysis: usual dose

Safety

• Adverse drug reactions include:
  • Acute kidney injury from crystal deposition, so maintain hydration
  • Phlebitis
  • Neurotoxicity, with lethargy, confusion, tremor, myoclonus, agitation, hallucinations, and extrapyramidal symptoms