What is the recommended acyclovir dosing for an otherwise healthy adult with a typical herpes simplex virus (HSV‑1 or HSV‑2) infection?

Acyclovir Dosing for Herpes Simplex (Shingles)

Critical Clarification: "Singles" vs. Shingles vs. HSV

If you are asking about herpes zoster (shingles), the recommended acyclovir dose is 800 mg orally five times daily for 7–10 days. 1

However, the term "singles" likely refers to herpes simplex virus (HSV) infection rather than herpes zoster. The dosing differs substantially between these conditions, so the remainder of this answer addresses HSV infection in otherwise healthy adults.

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First-Episode Genital Herpes

For initial genital HSV infection, the CDC recommends acyclovir 200 mg orally five times daily for 7–10 days, initiated as soon as possible after symptom onset. 2

• The FDA-approved regimen is 200 mg every 4 hours (5 times daily) for 10 days. 1
• Treatment should continue until clinical resolution is achieved. 2
• Intravenous acyclovir is not indicated unless the patient has severe disease requiring hospitalization or complications such as disseminated infection. 2

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Recurrent Genital Herpes (Episodic Treatment)

For recurrent genital HSV episodes, the CDC recommends acyclovir 800 mg orally twice daily for 5 days, initiated at the earliest sign of prodrome or within 2 days of lesion onset. 3, 2

Alternative Episodic Regimens:

• Acyclovir 400 mg orally three times daily for 5 days 3

• Acyclovir 200 mg orally five times daily for 5 days 1

• Early patient-initiated therapy at the first sign of prodrome yields the best results and may abort some episodes entirely. 4

• A 2-day course of acyclovir 800 mg three times daily has been shown to significantly reduce lesion duration and viral shedding compared to placebo. 5

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Suppressive Therapy for Frequent Recurrences

For patients with ≥6 recurrences per year, the CDC recommends acyclovir 400 mg orally twice daily for continuous suppression. 3, 6, 2

Key Points About Suppressive Therapy:

• This regimen reduces recurrence frequency by at least 75%. 3, 6
• The FDA approves suppressive therapy for up to 12 months, after which the patient should be re-evaluated to assess ongoing need. 1, 6
• Alternative suppressive regimens include acyclovir 200 mg orally 3–5 times daily. 6, 1
• Suppressive therapy reduces but does not eliminate asymptomatic viral shedding or transmission risk. 6

Common Pitfall:

• After 1 year of continuous suppression, discontinue therapy temporarily to reassess the patient's natural recurrence rate, as genital herpes frequency may change over time. 6, 1

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Orofacial Herpes (Cold Sores)

For moderate to severe oral HSV (gingivostomatitis) in adults, the CDC recommends acyclovir 400 mg orally three times daily for 5–10 days. 7, 3

• For mild gingivostomatitis, the same dose (400 mg three times daily) is appropriate. 7
• If hospitalization is required due to severe disease, initiate intravenous acyclovir 5–10 mg/kg every 8 hours, then transition to oral therapy once lesions begin to regress. 3

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Severe or Complicated HSV Requiring Hospitalization

For severe genital herpes with complications (e.g., extensive mucocutaneous involvement, inability to tolerate oral medication, or disseminated infection), the CDC recommends intravenous acyclovir 5–10 mg/kg every 8 hours for 5–7 days or until clinical improvement. 3, 2

Indications for IV Therapy:

• Disseminated HSV involving visceral organs (hepatitis, pneumonitis, encephalitis) 2
• Immunocompromised patients with prolonged, extensive outbreaks 2
• HSV encephalitis: 10 mg/kg IV every 8 hours for 10–21 days 3

Transition to Oral Therapy:

• Once lesions regress and systemic symptoms resolve, switch to acyclovir 400 mg orally three times daily until complete healing. 2

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Acyclovir-Resistant HSV

For acyclovir-resistant HSV (typically in immunocompromised patients), the CDC recommends foscarnet 40 mg/kg intravenously three times daily or 60 mg/kg twice daily. 7, 3, 2

• Resistance should be suspected if lesions persist despite standard acyclovir therapy, particularly in HIV-infected or transplant patients. 2, 8
• Topical trifluridine or cidofovir may be considered for accessible mucocutaneous lesions. 8

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Renal Dose Adjustment

Acyclovir is primarily renally excreted and requires dose adjustment in renal impairment. 2, 1

FDA-Recommended Adjustments for Oral Acyclovir:

• CrCl >10 mL/min: No adjustment for 200 mg every 4 hours 1

• CrCl 0–10 mL/min: 200 mg every 12 hours 1

• For 400 mg twice daily: Reduce to 200 mg every 12 hours if CrCl 0–10 mL/min 1

• For 800 mg every 4 hours:

  • CrCl 10–25 mL/min: 800 mg every 8 hours 1
  • CrCl 0–10 mL/min: 800 mg every 12 hours 1

• Hemodialysis: Administer an additional dose after each dialysis session. 1

• Ensure adequate hydration during therapy to prevent crystalluria. 3

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Important Caveats

• Topical acyclovir is ineffective for severe or systemic genital herpes and should not replace systemic therapy. 2
• Acyclovir does not eradicate latent virus or prevent future recurrences after discontinuation. 2
• Viral shedding and transmission can occur during asymptomatic periods despite therapy. 2
• In immunocompromised patients, higher doses (400 mg orally 3–5 times daily) and longer treatment duration (14 days or until complete resolution) are often required. 3, 6