Acyclovir Dosing for Cold Sores (Herpes Simplex Labialis)
For treating 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
Standard Treatment Regimens
- Treatment should be initiated during the prodrome or within 2 days of onset of lesions for maximum effectiveness 1
- Three equally effective oral acyclovir regimens for episodic treatment of cold sores:
- The 800 mg twice daily regimen may offer better compliance due to reduced frequency of dosing 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 1, 2
- In clinical trials, acyclovir cream reduced the mean duration of episodes by approximately 0.5 days compared to placebo 2
- Acyclovir treatment can shorten the duration of pain associated with cold sores 3, 2
- Most immunocompetent patients with recurrent disease experience limited benefit from therapy if treatment is not started early 1
- Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 1
Special Populations
Immunocompromised Patients
- HIV-infected or otherwise immunocompromised patients may require higher doses and longer treatment duration 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 1
Frequent Recurrences
- For patients with frequent recurrences (six or more per year), suppressive therapy may be considered 1
- Suppressive dosing: acyclovir 400 mg orally twice daily 1
- Suppressive therapy can reduce the frequency of herpes labialis recurrences by 50-78% 4
- After 1 year of continuous suppressive therapy, acyclovir should be discontinued to reassess the patient's rate of recurrent episodes 1
Alternative Approaches
- Some studies suggest a single "stat" dose of acyclovir 800 mg taken at the first sensory signs may prevent lesions from appearing in many patients 5
- However, this approach is not part of standard guidelines and requires further validation 1
Practical Advice
- Patients should avoid close contact while they have active lesions to prevent transmission 1
- Allergic reactions to acyclovir are infrequent 1
- Treatment is most effective when started at the earliest sign of a cold sore (tingling, burning, itching) 1, 3
- Even with optimal treatment, acyclovir may not completely prevent the development of classical lesions (progression to vesicles, ulcers, and/or crusts) 2