Acyclovir Dosing for Cold Sores (Herpes Labialis)
For cold sores, acyclovir 400 mg three times daily for 5 days is the recommended regimen, not 7 days. 1, 2
Correct Dosing Regimens
The CDC provides three equally effective options for treating recurrent oral herpes outbreaks, all for 5 days duration 1, 2:
- Acyclovir 400 mg orally 3 times daily for 5 days 1, 2
- Acyclovir 200 mg orally 5 times daily for 5 days 1, 2
- Acyclovir 800 mg orally 2 times daily for 5 days 1, 2
The 400 mg three times daily regimen you mentioned is correct in dosage and frequency, but the duration should be 5 days, not 7 days. 1, 2
Timing of Treatment Initiation
Treatment must be initiated during the prodrome or within 2 days of lesion onset for maximum benefit. 1, 2 Starting therapy after this window significantly reduces effectiveness, and most immunocompetent patients with recurrent disease experience limited benefit from delayed therapy. 1, 2
Alternative Regimens with Superior Convenience
For patients seeking more convenient dosing schedules 2:
- Acyclovir 800 mg twice daily for 5 days offers improved adherence while maintaining equivalent efficacy, demonstrating shorter symptom duration (8.1 vs 12.5 days with placebo, p=0.02) and reduced pain duration (2.5 vs 3.9 days with placebo, p=0.02) 2
- Valacyclovir 2 g twice daily for 1 day provides comparable efficacy with superior convenience, reducing episode duration by 1.0 day (p=0.001) compared to placebo 2, 3
Critical Caveats
Oral acyclovir is significantly more effective than topical formulations and should always be preferred. 2 Topical acyclovir is substantially less effective than systemic therapy and its use is discouraged. 1
Patients must understand that acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation. 1, 2 The medication treats the current outbreak but does not prevent future episodes.
Patients should abstain from activities that might spread the virus while lesions are present, though transmission can occur during asymptomatic periods. 1