C. diff Risk


Oral Bioavailability


Approximate Cost

General Information

Common Usage

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

Prophylaxis of herpesviral infections if recurrent disease or immunocompromised.

Drug Monitoring

Follow SCr as appropriate.

Check urine for crystals if AKI suspected.

Adverse Effects

  •  GI upset

  •  Phlebitis

  •  Increased SCr

  •  AKI from crystal nephropathy

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, which is more bioavailable with more convenient dosing.


Antimicrobial class: Antiviral. Nucleoside analogue.

Pregnancy category: B

Average serum half life: 3 hours, longer if renal dysfunction

CSF penetration: Therapeutic

Urine penetration: Therapeutic