What is the recommended preventative dose of acyclovir (antiviral medication) for herpes simplex virus (HSV) infections?

Acyclovir Preventative Dose for HSV Suppression

For daily suppressive therapy of recurrent genital herpes, acyclovir 400 mg orally twice daily is the recommended preventative dose, with treatment continued for up to 12 months followed by re-evaluation. 1, 2

Standard Suppressive Dosing Regimens

The CDC guidelines establish the following preventative dosing options for HSV suppression 1:

• Acyclovir 400 mg orally twice daily (preferred regimen) 1, 2
• Alternative: Acyclovir 200 mg orally 3-5 times daily 1
• Alternative: Valacyclovir 250 mg orally twice daily 1
• Alternative: Valacyclovir 500 mg orally once daily 1
• Alternative: Famciclovir 250 mg orally twice daily 1

Key Clinical Considerations

Efficacy and Duration:

• Suppressive therapy reduces HSV recurrence frequency by at least 75% in patients with frequent recurrences (≥6 episodes per year) 1
• Safety and efficacy have been documented for continuous daily therapy up to 5-10 years 1, 3
• After 1 year of continuous suppressive therapy, acyclovir should be discontinued to reassess the patient's recurrence rate 1, 2

Important Limitations:

• Suppressive acyclovir reduces but does not eliminate asymptomatic viral shedding 1
• The extent to which suppressive therapy prevents HSV transmission remains unknown 1
• Acyclovir does not eradicate latent virus or affect subsequent risk, frequency, or severity of recurrences after discontinuation 4, 5

Dose Adjustment for Special Populations

Renal Impairment: For patients with creatinine clearance 0-10 mL/min/1.73 m², the 400 mg twice daily regimen should be reduced to 200 mg every 12 hours 2

HIV-Infected/Immunocompromised Patients:

• Higher doses are often beneficial: acyclovir 400 mg orally 3-5 times daily 1
• Famciclovir 500 mg twice daily has been effective in decreasing recurrence rates and subclinical shedding in HIV-infected patients 1
• Acyclovir resistance occurs in approximately 5% of immunocompromised patients versus <0.5% in immunocompetent patients 3

Dosing Strategy Algorithm

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

1. Start with acyclovir 400 mg orally twice daily 1, 2
2. Continue for up to 12 months 2
3. Discontinue and reassess recurrence frequency 1, 2
4. If recurrences remain frequent, resume suppressive therapy 1

For patients seeking lowest effective dose:

• Begin with 400 mg twice daily, then titrate down to identify the minimum dose providing symptom relief 1
• Research demonstrates that reducing from 200 mg four times daily to lower doses progressively shortens time to first recurrence 6

Common Pitfalls to Avoid

• Do not use valacyclovir 500 mg once daily in patients with very frequent recurrences (≥10 episodes per year), as this regimen appears less effective than other dosing options 1
• Avoid high-dose valacyclovir (8 g/day) in immunocompromised patients due to association with hemolytic uremic syndrome or thrombotic thrombocytopenic purpura 1
• Do not expect complete prevention of transmission or asymptomatic shedding with suppressive therapy 1