C. diff Risk


Oral Bioavailability


Approximate Cost

IV: $$$$
PO: $

Spectrum Of Activity


5-10mg/kg IV q8h. Consider higher dosing for serious infections such as CNS and disseminated zoster

800mg PO 5 times per day for shingles

Prophylaxis dosing varies by indication

General Information

Common Usage

Therapy for herpesviral infections (HSV and VZV) including encephalitis

Prophylaxis of herpesviral infections if recurrent disease or immunocompromised

Drug Monitoring


  • Cr twice weekly with IV acyclovir (dose adjustment and nephrotoxicity assessment)


  • Phlebitis

  • CNS effects (IV)

  • GI effects

  • Ensure adequate hydration for IV acyclovir

Adverse Effects

  • Malaise

  • Nausea

  • Vomiting

  • Diarrhea

  • Phlebitis (with IV acyclovir)

  • Nephrotoxicity

  • CNS effects with high-dose IV therapy

Major Interactions

Mycophenolate can increase the acyclovir concentration

May diminish efficacy of zoster or varicella vaccine

Additional Information

For oral indications, Valacyclovir is the pro-drug and is more bioavailable with more convenient dosing


Antimicrobial class: Antiviral, nucleoside analogue

Pregnancy category: B

Average serum half life: 3 hours

CSF penetration: Therapeutic

Urine penetration: Therapeutic