What is the recommended dose of acyclovir (antiviral medication) for treating fever blisters?

Acyclovir Dosing for Fever Blisters (Cold Sores)

For fever blisters (cold sores), the recommended dosage of oral acyclovir is 400 mg three times daily for 5 days, 200 mg five times daily for 5 days, or 800 mg twice daily for 5 days. 1

Treatment Recommendations

• Treatment should be initiated during the prodrome or within 2 days of lesion onset for maximum effectiveness 2, 1
• Three equally effective oral acyclovir regimens for episodic treatment of cold sores:
  • 400 mg orally three times daily for 5 days 2, 1
  • 200 mg orally five times daily for 5 days 2, 1
  • 800 mg orally twice daily for 5 days 2, 1
• The 800 mg twice daily regimen may offer better compliance due to reduced dosing frequency 1

Clinical Considerations

• Early treatment initiation is crucial - starting therapy at the first sign of symptoms provides the greatest benefit 1
• Oral acyclovir is significantly more effective than topical formulations for treating cold sores 2
• Most immunocompetent patients with recurrent disease experience limited benefit from therapy if treatment is not started early 3, 1
• Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 2, 1

Special Populations

Immunocompromised Patients

• HIV-infected or otherwise immunocompromised patients may require higher doses and longer treatment courses 2, 1
• For immunocompromised patients, recommended dosing: acyclovir 400 mg orally three to five times daily until clinical resolution 1
• For severe cases in immunocompromised patients, intravenous therapy may be required: acyclovir 5-10 mg/kg IV every 8 hours 3, 1

Patients with Frequent Recurrences

• For patients with six or more recurrences per year, suppressive therapy may be considered 3
• Suppressive dosing: acyclovir 400 mg orally twice daily 3, 1
• Alternative suppressive regimen: acyclovir 200 mg orally 3-5 times daily 3

Practical Advice

• Patients should avoid close contact while they have active lesions to prevent transmission 1
• Treatment is most effective when started at the first sign of symptoms (tingling, burning, itching) before visible lesions appear 2, 1
• If treatment cannot be initiated early, the benefits may be limited for immunocompetent patients 3, 1
• Allergic reactions to acyclovir are infrequent 1