C difficile risk
Oral Bioavailability
Oral: $ IV:$$


CrCl <10CrCl 10 - 24CrCl 25 - 50IV: 5mg/kg IV q24h, or half of regular dose q24h
PO: 200-800 mg PO q12hIV: 10mg/kg IV q24h
PO standard dose: 400 mg PO q8h
PO high dose: 800 mg PO q8hIV: 10mg/kg IV q12h
PO: no changes

2.5-5mg/kg IV q24h

Consider loading dose for serious infections
Schedule doses so doses are given after HD

5-7.5mg/kg IV q24h

Use upper end for CNS infections

1 to < 3 months3 months to < 12 years12 years and older20 mg/kg/dose IV q8h10-15 mg/kg/dose IV q8h10 mg/kg/dose IV q8h

IntravenousOral500 mg/m2/dose IV q8h OR 10-15 mg/kg/dose IV q8h2 years and older: 20 mg/kg/dose 4 times/day

IntravenousOral5 mg/kg/dose IV q8h20 mg/kg/dose PO TID up to 400 mg PO TID

Serious Infections

  • e.g. CNS and Disseminated Zoster

  • 10mg/kg IV q8h

  • Use adjusted body weight for obese patients


  • 800mg PO 5 times per day

  • Use valacyclovir instead

Prophylaxis and HSV mucocutaneous dosing varies by indication

  • Commonly used dose for mucocutaneous HSV: 400 mg PO TID

  • Commonly used dose for prophylaxis: 400-800 mg PO BID

General Information

Therapy for herpesviral infections (HSV and VZV) including encephalitis.

Prophylaxis of herpesviral infections if recurrent disease or immunocompromised.

Follow SCr as appropriate.

Check urine for crystals if AKI suspected.

  • ¬†GI upset

  • ¬†Phlebitis

  • ¬†Increased SCr

  • ¬†AKI from crystal nephropathy

Mycophenolate can increase the acyclovir concentration.

May diminish efficacy of zoster live or varicella vaccine.

For oral indications, valacyclovir is the pro-drug, which is more bioavailable with more convenient dosing.

Antimicrobial class: Antiviral. Nucleoside analogue.

Pregnancy category: B

Average serum half life: 3 hours

CSF penetration: Therapeutic with IV formulation

Urine penetration: Therapeutic