What is the recommended acyclovir (antiviral medication) dosing regimen for an adult patient with genital herpes?

Acyclovir Dosing for Adult Genital Herpes

For first-episode genital herpes, treat with acyclovir 200 mg orally 5 times daily for 7-10 days; for recurrent episodes, use 800 mg orally twice daily for 5 days initiated at prodrome or within 2 days of lesion onset; and for patients with ≥6 recurrences per year, prescribe suppressive therapy with 400 mg orally twice daily. 1, 2, 3

First Clinical Episode (Primary Infection)

• Administer acyclovir 200 mg orally 5 times daily for 7-10 days or until clinical resolution is achieved. 4, 2, 3
• This regimen is FDA-approved and reduces viral shedding, new lesion formation, and duration of symptoms including pain, dysuria, and malaise. 3, 5
• For severe disease requiring hospitalization (disseminated infection, encephalitis, pneumonitis, or hepatitis), escalate to intravenous acyclovir 5-10 mg/kg every 8 hours for 5-7 days. 4, 1, 2

Recurrent Episodes

The CDC recommends three equally effective oral regimens, all for 5 days duration: 1, 2

• Acyclovir 800 mg orally twice daily (most convenient, best adherence) 1, 3, 6
• Acyclovir 400 mg orally 3 times daily 4, 1, 3
• Acyclovir 200 mg orally 5 times daily 4, 1, 3

Critical Timing Considerations

• Treatment must be initiated during prodrome or within 2 days of lesion onset for maximum benefit. 1, 2, 3
• Patient-initiated therapy at the earliest sign of recurrence is most effective and may abort episodes in some patients. 7, 6
• Most immunocompetent patients experience limited benefit when treatment is delayed beyond this window. 4, 2

Chronic Suppressive Therapy

For patients with frequent recurrences (≥6 episodes per year): 4, 1

• Prescribe acyclovir 400 mg orally twice daily, which reduces recurrence frequency by at least 75%. 4, 1, 3
• Alternative regimen: 200 mg orally 3-5 times daily, titrating to the lowest effective dose. 4, 3
• After 12 months of continuous suppressive therapy, discontinue acyclovir to reassess the patient's recurrence rate, as the natural history may change over time. 4, 3
• Safety and efficacy have been documented for up to 5 years of continuous use. 4

Important Caveats for Suppressive Therapy

• Suppressive therapy does not eliminate asymptomatic viral shedding or prevent transmission to partners. 4
• Acyclovir-resistant HSV strains have been isolated from patients on suppressive therapy but are not associated with treatment failure in immunocompetent patients. 4

Renal Dose Adjustments

For patients with renal impairment, modify dosing based on creatinine clearance: 3

• CrCl >10 mL/min: 200 mg every 4 hours (5x daily) remains unchanged 3
• CrCl 0-10 mL/min: 200 mg every 12 hours 3
• For 400 mg twice daily regimen with CrCl 0-10 mL/min: reduce to 200 mg every 12 hours 3
• For 800 mg regimen: CrCl 10-25 mL/min use 800 mg every 8 hours; CrCl 0-10 mL/min use 800 mg every 12 hours 3
• Hemodialysis patients: Administer an additional dose after each dialysis session, as hemodialysis reduces plasma concentrations by 60%. 3

Common Pitfalls to Avoid

• Never use topical acyclovir as primary therapy—it provides no improvement in systemic symptoms and is significantly less effective than oral formulations. 2, 7
• Do not prescribe episodic treatment for patients with frequent recurrences; they are better managed with suppressive therapy. 4, 7
• Counsel patients that acyclovir does not eradicate latent virus or prevent future recurrences after discontinuation. 7, 5
• Advise patients to abstain from sexual activity while lesions are present, though transmission can occur during asymptomatic periods. 4, 2

Special Population Considerations

• Women of childbearing age must inform obstetric providers about HSV infection due to neonatal transmission risk. 4, 2
• Immunocompromised patients (including HIV-infected individuals) may require higher doses (400 mg orally 3-5 times daily) and prolonged treatment courses. 1, 2, 7
• Be vigilant for acyclovir resistance in immunocompromised patients if lesions persist despite therapy; consider foscarnet 40 mg/kg IV 3 times daily as alternative. 1, 7