Acyclovir Dosing for Cold Sores
For cold sores (herpes labialis), use acyclovir 800 mg orally twice daily for 5 days, initiated at the first sign of prodrome or within 2 days of lesion onset. 1, 2
Recommended Dosing Regimens
The CDC recommends three equally effective oral acyclovir regimens for episodic treatment of cold sores 1, 2:
- Acyclovir 800 mg orally twice daily for 5 days (preferred for convenience and adherence) 1, 2
- Acyclovir 400 mg orally three times daily for 5 days 1, 2
- Acyclovir 200 mg orally five times daily for 5 days 1, 2
The 800 mg twice-daily regimen offers the best balance of efficacy and convenience, demonstrating shorter symptom duration (8.1 days vs 12.5 days with placebo), reduced pain duration (2.5 days vs 3.9 days with placebo), and fewer lesions developing (7% vs 26% with placebo) 1.
Critical Timing Considerations
- Treatment must be initiated during the prodrome or within 2 days of lesion onset for maximum benefit 1, 2
- Early treatment at the first sign of symptoms (tingling, burning, itching) provides the greatest therapeutic advantage 2
- Delayed initiation significantly reduces treatment effectiveness 1, 2
Important Clinical Caveats
Limitations of therapy:
- Oral acyclovir is significantly more effective than topical formulations 1, 2
- Most immunocompetent patients with recurrent disease experience limited benefit from therapy 1, 2
- Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 1, 2
Patient counseling:
- Patients should abstain from activities that might spread the virus while lesions are present 1, 2
- Allergic reactions to acyclovir are infrequent 2
Special Populations
Immunocompromised patients:
- May require higher doses: acyclovir 400 mg orally three to five times daily until clinical resolution 2
- For severe cases, intravenous therapy may be necessary: acyclovir 5-10 mg/kg IV every 8 hours 2
Frequent recurrences (>6 episodes per year):
- Consider suppressive therapy: acyclovir 400 mg orally twice daily 2
Alternative Medications
If considering alternatives for improved convenience: