Infectious Disease Compendium

Acyclovir (Zovirax®)


CrCl Formula

CrCl > 80: 200 - 800 mg 2-5 x day po.

CrCl 80-50: 5-12 mg/kg q 8 h iv.

CrCl 50-10: 5-12 mg/kg q 12-24 h iv.

CrCl < 10: 2.5 - 6 mg/kg q 24 h iv. Hemodialysis: 500 mg after dialysis. Peritoneal dialysis: 2.5 mg/kg/day.

Important side effects

Keep well hydrated, causes acute renal failure from IV acyclovir crystal deposition in the kidneys. Agitation, confusion, dizziness, hallucinations, somnolence (more common in the elderly)

Important drug interactions

Cyclosporine increases nephrotoxicity; aminoglycosides increases nephrotoxicity and/or neurotoxicity; cimetidine increases acyclovir toxicity; increases meperidine effect; decreases phenytoin effect; zidovudine increases neurotoxicity (drowsiness and lethargy (:the Grand Rounds Effect:))

Rants and Screeds

Note: valacyclovir, famciclovir are better absorbed acyclovir. Same drug though.

Use for

Herpes simplex 1 and 2; Varicella Zoster (aka shingles). CMV prophylaxis in the transplant patient, although it shouldn't work. In terms of MIC for herpes virus, from most to least sensitive: HSV 1 < HSV 2 < VZV.

Don't use for


Thymidine analog.

Curious Cases

Relevant links to my Medscape blog