Oral Acyclovir Dosage for Cold Sores
For treating cold sores (herpes labialis), the CDC recommends 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 Options
The CDC provides three equally effective dosing regimens for cold sores, all administered for 5 days 1:
- Acyclovir 800 mg orally twice daily (preferred for convenience and adherence) 1
- Acyclovir 400 mg orally 3 times daily 1
- Acyclovir 200 mg orally 5 times daily 1
Timing of Treatment Initiation
Treatment must be started during the prodrome or within 2 days of lesion onset for maximum benefit. 1 Delaying treatment beyond this window significantly reduces efficacy.
Expected Clinical Outcomes
When using the 800 mg twice-daily regimen 1:
- Symptom duration decreases from 12.5 days (placebo) to 8.1 days (p=0.02) 1
- Pain duration reduces from 3.9 days to 2.5 days (p=0.02) 1
- Lesion development is prevented in 19-26% more patients compared to placebo 1
Alternative Antiviral Options
If improved convenience is desired, consider 1:
- Valacyclovir 2 g twice daily for 1 day (comparable efficacy with superior convenience) 1, 2
- Famciclovir 1500 mg single dose (reduces healing time from 6.2 to 4.4 days, p<0.001) 1
Critical Counseling Points
Patients must understand that acyclovir does not eradicate latent virus and will not affect the frequency, severity, or risk of future recurrences after discontinuation. 1 This is a common misconception that leads to unrealistic treatment expectations.
- Abstain from activities that might spread the virus while lesions are present 1
- Oral formulations are significantly more effective than topical acyclovir 1
- Most immunocompetent patients experience limited benefit from therapy, though treatment still provides measurable symptom reduction 1
Special Population Considerations
For immunocompromised patients, oral or intravenous antiviral therapy is mandatory rather than topical treatment due to risk of severe and prolonged episodes. 1