Infectious Disease Compendium

Acyclovir (Zovirax®)

Dosing

CrCl Formula

CrCl > 80: 200 - 800 mg 2-5 x day po depending on syndrome. IV for the immunoincompetent.

Genital Herpes

Initial treatment: 200 mg po 5 x daily for 10 days or 400 mg po q8 for 7-10 days.

Intermittent treatment for recurrence: 200 mg po 5 x daily for 5 days; initiate at the earliest sign or symptom of recurrence.

Chronic suppression for recurrence: 400 mg po bid or 200 mg 3-5 times daily.

Herpes Zoster

Shingles: 800 mg 5 times a day for 7-10 days.

10-15 mg/kg iv q 8 for Herpes simplex encephalitis for 2-3 weeks.

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. I have seen it with po acyclovir.

Nephrotoxicity is associated with obesity and vancomycin (PubMed).

Agitation, confusion, dizziness, hallucinations, somnolence (more common in the elderly).

Important drug interactions

Cyclosporine increases nephrotoxicity; aminoglycosides increase 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 or chickenpox).

In terms of the MIC for herpes virus, from most to least sensitive: HSV 1 < HSV 2 < VZV.

Thymidine kinase negative mutant HSV can occur and are resistant.

Class

Thymidine analog.

Curious Cases

Relevant links to my Medscape blog

Dilemmata

Last Update: 04/26/19.