What is the recommended dosing for Acyclovir (antiviral medication) in adults with Herpes Simplex Virus (HSV) or Varicella-Zoster Virus (VZV) infections?

Acyclovir Dosing for HSV and VZV Infections in Adults

The recommended dosing of acyclovir for adults with HSV or VZV infections varies by clinical presentation, with first episodes of genital herpes requiring 200 mg orally 5 times daily for 7-10 days, recurrent episodes requiring 200 mg orally 5 times daily for 5 days (or alternative regimens), and suppressive therapy requiring 400 mg orally twice daily for frequent recurrences. 1, 2, 3

Initial HSV Infections

First Clinical Episode of Genital Herpes

• Standard regimen: Acyclovir 200 mg orally 5 times daily for 7-10 days or until clinical resolution 1
• Alternative regimens:
  • Acyclovir 400 mg orally 3 times daily for 7-10 days 2, 3
  • Treatment should be continued until clinical healing is achieved 2

First Clinical Episode of Herpes Proctitis

• Acyclovir 400 mg orally 5 times daily for 10 days or until clinical resolution 1

Recurrent HSV Episodes

Episodic Treatment

• Start at first sign of prodrome or within 1-2 days of lesion onset 2
• Recommended regimens:
  • Acyclovir 200 mg orally 5 times daily for 5 days 1
  • Acyclovir 400 mg orally 3 times daily for 5 days 1
  • Acyclovir 800 mg orally 2 times daily for 5 days 1, 2

Note: Starting treatment beyond 1-2 days after onset significantly reduces effectiveness by ≥50% 2

Suppressive Therapy

• Indicated for: Patients with ≥6 recurrences per year 1, 2
• Recommended regimen: Acyclovir 400 mg orally twice daily 1, 2
• Alternative regimen: Acyclovir 200 mg orally 3-5 times daily 1, 2
• Duration: Up to 12 months, followed by reassessment 3
• After 1 year of continuous suppressive therapy, discontinue to assess recurrence rate 1, 2

Varicella-Zoster Virus (VZV) Infections

Herpes Zoster (Shingles)

• Recommended regimen: Acyclovir 800 mg orally 5 times daily for 7-10 days 2, 3, 4
• Treatment should be initiated as soon as possible after symptom onset 2

Chickenpox

• Adults: Acyclovir 800 mg orally 4 times daily for 5 days 3
• Treatment should be initiated at the earliest sign or symptom 3

Severe Disease Requiring Hospitalization

Severe HSV or Disseminated Infection

• Recommended regimen: Acyclovir 5-10 mg/kg IV every 8 hours for 5-7 days or until clinical resolution 1, 5

Severe VZV Infection in Immunocompromised Patients

• Acyclovir 500 mg/m² IV every 8 hours for 7 days 5

Dosage Adjustment for Renal Impairment

Oral Acyclovir

Creatinine Clearance	200 mg Regimen	400 mg Regimen	800 mg Regimen
>10 mL/min/1.73m²	200 mg every 4 hours	400 mg every 12 hours	800 mg every 4 hours
0-10 mL/min/1.73m²	200 mg every 12 hours	200 mg every 12 hours	800 mg every 12 hours

IV Acyclovir

• Dosage adjustment is necessary based on creatinine clearance 5
• Adequate hydration during treatment is essential to minimize nephrotoxicity risk 2

Important Clinical Considerations

• Acyclovir neither eradicates latent virus nor affects subsequent risk after discontinuation 1, 2
• Suppressive therapy reduces but does not eliminate asymptomatic viral shedding 2
• Immunocompromised patients may require higher doses and longer treatment courses 2
• Patients should be advised to abstain from sexual activity while lesions are present 1
• Topical acyclovir therapy is substantially less effective than oral therapy and is not recommended 1
• For acyclovir-resistant HSV (primarily in immunocompromised patients), foscarnet 40 mg/kg IV three times daily or 60 mg/kg IV twice daily is recommended 1, 6
• Monitor for neurological symptoms that may indicate acyclovir neurotoxicity, especially in patients with renal impairment 2