What is the recommended dosage of acyclovir (Antiviral medication) for the treatment of Herpes Simplex Virus (HSV) infections, a type of Sexually Transmitted Disease (STD)?

Acyclovir Dosing for HSV Sexually Transmitted Infections

For first-episode genital HSV, use acyclovir 400 mg orally 5 times daily for 10 days; for recurrent episodes, use 800 mg orally twice daily for 5 days; and for chronic suppression in patients with frequent recurrences (≥6 per year), use 400 mg orally twice daily. 1, 2

First Episode Genital Herpes

• Administer acyclovir 400 mg orally 5 times daily for 10 days or until clinical resolution 3
• Alternative dosing from older guidelines includes 200 mg orally 5 times daily for 7-10 days, though the higher dose is now preferred 4
• 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 3, 1, 4

Recurrent Episodes

Three equally effective oral regimens are available, all for 5 days duration: 1, 4, 2

• Acyclovir 800 mg orally twice daily (most convenient, best adherence) 1, 2
• Acyclovir 400 mg orally 3 times daily 1, 4, 2
• Acyclovir 200 mg orally 5 times daily 3, 1, 4

Critical timing consideration: Treatment must be initiated during prodrome or within 2 days of lesion onset for maximum benefit 1, 4. Starting therapy after this window significantly reduces effectiveness, and most immunocompetent patients with delayed treatment experience limited benefit 3, 1.

A shorter 2-day course (800 mg orally 3 times daily for 2 days) has demonstrated efficacy in reducing lesion duration (4 days vs 6 days with placebo, p=0.001) and represents a convenient alternative 5.

Chronic Suppressive Therapy

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

• Primary regimen: Acyclovir 400 mg orally twice daily 3, 1, 2
• Alternative regimen: 200 mg orally 3-5 times daily, titrated to the lowest effective dose 3, 1
• Suppressive therapy reduces recurrence frequency by at least 75% 3, 1
• After 1 year of continuous therapy, discontinue acyclovir to reassess the patient's recurrence rate 3, 2

Long-term safety and efficacy have been documented for up to 5 years of continuous use 3. In a landmark trial, 44% of patients on suppressive therapy (400 mg twice daily) remained recurrence-free for one year versus only 2% on episodic treatment 6.

Special Populations

Immunocompromised patients (including HIV-infected individuals):

• Require higher doses: 400 mg orally 3-5 times daily for suppression 1
• May need prolonged treatment courses (14 days or until complete resolution) 1
• Monitor for acyclovir-resistant strains, which may necessitate foscarnet 40 mg/kg IV 3 times daily or 60 mg/kg IV twice daily 1, 7

Pregnant women with recurrent genital herpes:

• Suppressive therapy with acyclovir 400 mg orally 3 times daily after 36 weeks gestation significantly reduces clinical HSV at delivery (6% vs 14% with placebo, p=0.046) 8

Renal Impairment Dosing

Adjust doses based on creatinine clearance: 2

• CrCl >10 mL/min: 200 mg every 12 hours (for 200 mg q4h regimen)
• CrCl 0-10 mL/min: 200 mg every 12 hours (for 200 mg q4h regimen)
• For 800 mg q4h regimen: Reduce to 800 mg every 8 hours if CrCl 10-25 mL/min, or 800 mg every 12 hours if CrCl 0-10 mL/min 2
• Hemodialysis patients: Administer an additional dose after each dialysis session 2

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 4, 9
• Counsel patients that acyclovir does not eradicate latent virus or prevent future recurrences after discontinuation 1, 9
• Advise abstinence from sexual activity while lesions are present, though transmission can occur during asymptomatic periods 3, 4
• Women of childbearing age must inform obstetric providers about HSV infection due to neonatal transmission risk 3, 4