What is the dose of acyclovir for the treatment of herpes?

Treatment of Herpes and Acyclovir Dosing

For herpes treatment, acyclovir remains the cornerstone antiviral therapy with specific dosing regimens that vary by infection type, severity, and whether it's initial or recurrent disease.

Oral Herpes (Herpes Labialis/Cold Sores)

For recurrent oral herpes outbreaks, the CDC recommends three equally effective 5-day regimens: 1, 2

• Acyclovir 800 mg orally twice daily for 5 days (most convenient) 1, 2
• Acyclovir 400 mg orally three times daily for 5 days 1, 2
• Acyclovir 200 mg orally five times daily for 5 days 1, 2

Critical timing consideration: Treatment must be initiated during the prodrome or within 2 days of lesion onset for maximum benefit, as delayed therapy significantly reduces effectiveness. 2

Expected outcomes with the 800 mg twice-daily regimen include: 2

• Shorter symptom duration (8.1 days vs 12.5 days with placebo)
• Reduced pain duration (2.5 days vs 3.9 days with placebo)
• Fewer lesions developing (7% vs 26% with placebo)

Genital Herpes

First Clinical Episode

For initial genital herpes, treat for 7-10 days with one of these regimens: 3, 4

• Acyclovir 400 mg orally three times daily 3
• Acyclovir 200 mg orally five times daily 3, 4
• Extend treatment if healing is incomplete after 10 days 3

The FDA label specifies 200 mg every 4 hours, 5 times daily for 10 days for initial genital herpes. 4

Recurrent Episodes

For recurrent genital herpes, treat for 5 days with: 1, 3

• Acyclovir 800 mg orally twice daily (most convenient) 1, 3
• Acyclovir 400 mg orally three times daily 1, 3
• Acyclovir 200 mg orally five times daily 3

A 2-day course of acyclovir 800 mg three times daily has also demonstrated efficacy, significantly reducing lesion duration (4 days vs 6 days with placebo) and viral shedding (25 hours vs 58.5 hours). 5

Suppressive Therapy

For patients with frequent recurrences (≥6 episodes per year), use daily suppressive therapy: 1, 3

• Acyclovir 400 mg orally twice daily 1, 3, 4
• This reduces recurrence frequency by ≥75% 1, 3
• After 1 year of suppressive therapy, discontinue to reassess recurrence frequency 3, 4

The FDA label notes alternative suppressive regimens ranging from 200 mg three times daily to 200 mg five times daily, though 400 mg twice daily is most commonly recommended. 4

Herpes Zoster (Shingles)

For acute herpes zoster, the FDA-approved regimen is: 4

• Acyclovir 800 mg orally every 4 hours, 5 times daily for 7-10 days 4

Severe HSV Disease Requiring Hospitalization

For severe disease, complications, or immunocompromised patients requiring hospitalization: 1

• Acyclovir 5-10 mg/kg IV every 8 hours for 5-7 days or until clinical improvement 1
• For CNS disease in children: 10 mg/kg IV three times daily for 21 days 1

Pediatric Dosing

For children with mucocutaneous HSV infections: 1

• Acyclovir 20 mg/kg orally three times daily (maximum 400 mg/dose) for 7-14 days 1
• For children <45 kg with first episode genital herpes: 20 mg/kg (max 400 mg/dose) orally three times daily for 5-14 days 1

For chickenpox in children ≥2 years: 4

• 20 mg/kg per dose orally four times daily (80 mg/kg/day) for 5 days 4
• Children >40 kg should receive adult dose of 800 mg four times daily for 5 days 4

Renal Impairment Dosing

Dose adjustments are mandatory in renal impairment, as acyclovir is primarily renally excreted: 1, 4

For 800 mg every 4 hours regimen: 4

• CrCl >25: 800 mg every 4 hours, 5 times daily
• CrCl 10-25: 800 mg every 8 hours
• CrCl 0-10: 800 mg every 12 hours

For 400 mg every 12 hours regimen: 4

• CrCl >10: 400 mg every 12 hours
• CrCl 0-10: 200 mg every 12 hours

For hemodialysis patients: Administer an additional dose after each dialysis session, as hemodialysis reduces plasma concentrations by 60% over 6 hours. 4

Important Clinical Caveats

Patient counseling is essential: 2, 3

• Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 2, 3
• Sexual transmission can occur during asymptomatic periods due to viral shedding 3
• Abstain from sexual activity when lesions or prodromal symptoms are present 3

Topical acyclovir is substantially less effective than oral therapy and is not recommended. 3

For immunocompromised patients: 1

• Consider higher doses (400 mg orally 3-5 times daily) and longer treatment duration 1
• Be vigilant for acyclovir resistance if lesions persist despite therapy 1

For acyclovir-resistant HSV: Foscarnet 40 mg/kg IV three times daily or 60 mg/kg IV twice daily is the treatment of choice. 1

High-dose valacyclovir (8 g/day) should be avoided in immunosuppressed patients due to risk of hemolytic-uremic syndrome or thrombotic thrombocytopenic purpura. 1