Acyclovir Dosing for Cold Sore Outbreaks
For cold sore outbreaks, use acyclovir 800 mg orally twice daily for 5 days, which offers the best balance of efficacy and convenience while maintaining equivalent clinical outcomes to more frequent dosing regimens. 1
Recommended Dosing Regimens
The CDC provides three equally effective dosing options for cold sore treatment, all for 5 days duration 1:
- Acyclovir 800 mg orally twice daily - This is the preferred regimen due to superior convenience and adherence while maintaining equivalent efficacy 1
- Acyclovir 400 mg orally 3 times daily 1
- Acyclovir 200 mg orally 5 times daily 1, 2
Timing of Treatment Initiation
Treatment must be initiated during the prodrome or within 2 days of lesion onset for maximum benefit. 1, 3
- Starting treatment early is critical - the 800 mg twice-daily regimen demonstrates significantly shorter symptom duration (8.1 days vs 12.5 days with placebo, p=0.02) and reduced mean pain duration (2.5 days vs 3.9 days with placebo, p=0.02) when initiated promptly 1
- Early treatment also prevents lesion development in a higher proportion of patients (7% vs 26% with placebo) 1
Alternative Antiviral Options
If improved convenience is a priority, consider these alternatives 1:
- Valacyclovir 2 g twice daily for 1 day - Provides comparable efficacy with superior convenience compared to 5-day acyclovir regimens 1, 4
- Famciclovir 1500 mg single dose - Significantly reduces healing time (4.4 days vs 6.2 days with placebo, p<0.001) 1
Critical Caveats
- Oral formulations are significantly more effective than topical acyclovir - topical formulations should not be used as primary therapy for cold sores 1
- Most immunocompetent patients with recurrent cold sores experience limited benefit from therapy, though treatment still reduces symptom duration and severity 1
- Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 1, 3
- Patients should abstain from activities that might spread the virus while lesions are present 1, 3
Special Population Considerations
- Immunocompromised patients require oral or even intravenous antiviral therapy rather than topical treatment due to risk of more severe and prolonged episodes 1
- HIV-infected patients may require more aggressive therapy with higher doses (400 mg five times daily for 5 days, then 400 mg three times daily for 1-2 months, followed by 400 mg twice daily for suppression) 5