What is the recommended dose of Acyclovir for treating herpes zoster?

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Last updated: July 2, 2025View editorial policy

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From the Guidelines

The recommended dose of Acyclovir for treating herpes zoster is 800 mg taken orally five times daily for 7-10 days, with treatment starting as soon as possible after symptom onset, ideally within 72 hours of rash appearance, for maximum effectiveness. This dose is based on the efficacy of acyclovir in accelerating the rate of cutaneous healing and reducing the severity of acute pain in adults with herpes zoster, as noted in studies such as 1. Key points to consider when treating herpes zoster with acyclovir include:

  • Starting treatment within 72 hours of rash onset for optimal results
  • Maintaining adequate hydration to prevent kidney issues, particularly with intravenous administration
  • Considering dose adjustments for patients with reduced kidney function
  • The potential for intravenous acyclovir in severe cases or for immunocompromised patients at a dose of 10 mg/kg every 8 hours for 7-10 days. Acyclovir's mechanism of action, inhibiting viral DNA synthesis to prevent herpes zoster virus replication, underlines its effectiveness in reducing the severity and duration of the rash, decreasing acute pain, and potentially lowering the risk of postherpetic neuralgia, as supported by the findings in 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Acute Treatment of Herpes Zoster: 800 mg every 4 hours orally, 5 times daily for 7 to 10 days. The recommended dose of Acyclovir for treating herpes zoster is:

  • 800 mg every 4 hours orally,
  • 5 times daily for 7 to 10 days 2.

From the Research

Recommended Dose of Acyclovir for Herpes Zoster

The recommended dose of Acyclovir for treating herpes zoster is:

  • 800 mg five times daily for 7-10 days 3, 4, 5 Some studies have also compared the efficacy of Acyclovir with other antiviral agents, such as famciclovir and valacyclovir, and found them to be comparable or superior in some aspects 6, 7

Comparison with Other Antiviral Agents

  • Famciclovir 500 mg three times daily for 7 days was found to be comparable to Acyclovir 800 mg five times daily for 7 days in terms of accelerating lesion resolution and reducing the duration of postherpetic neuralgia 6
  • Valacyclovir 1,000 mg three times daily for 7 days was found to be superior to Acyclovir 800 mg five times daily for 7 days in terms of accelerating the resolution of herpes zoster-associated pain and reducing the duration of postherpetic neuralgia 7

Duration of Treatment

  • The duration of treatment with Acyclovir for herpes zoster is typically 7-10 days 3, 4, 5
  • Some studies have investigated the efficacy of longer treatment durations, such as 21 days, but found no significant benefits over standard 7-day treatment 4

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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