C. diff Risk


Oral Bioavailability


Approximate Cost



Serious HSV/VZV Infections (e.g. CNS Infections and Disseminated Herpes Zoster)
10mg/kg IV q8h

Herpes zoster
800mg PO five times per day

Prophylaxis dosing varies by indication

General Information

Common Usage

Acyclovir is used to treat herpes virus infections (e.g. HSV and VZV) but not CMV infections.

Acyclovir is also used for prophylaxis in transplantation protocols for patients who are immunocompromised.

Drug Monitoring

Monitor serum creatinine and monitor for neurotoxicity.

Adverse Effects

  • ¬†Gastrointestinal intolerance

  • ¬†Phlebitis with IV formulation

  • ¬†Increased serum creatinine and hematuria secondary to crystal nephropathy

Major Interactions

Mycophenolate can increase serum concentrations of acyclovir.

Additional Information

For indications when oral acyclovir can be used, 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

Urine penetration: Therapeutic