What medication is recommended for a patient with a diagnosis of cold sores, likely caused by the herpes simplex virus?

Medication for Cold Sores

For cold sores (herpes labialis), valacyclovir 2 grams twice daily for 1 day (two doses taken 12 hours apart) is the recommended first-line treatment, initiated at the earliest symptom such as tingling, itching, or burning. 1

Treatment Algorithm

First-Line Therapy: Valacyclovir

• Valacyclovir 2 grams orally twice daily for 1 day (total of 2 doses, 12 hours apart) is FDA-approved and represents the most convenient, evidence-based regimen 1
• This high-dose, short-duration regimen reduces episode duration by approximately 1 day compared to placebo and is more convenient than alternative therapies 2
• Treatment must be initiated at the first symptom (prodrome: tingling, itching, burning) before visible lesions develop for optimal effectiveness 1
• Efficacy has not been established once clinical signs (papule, vesicle, ulcer) have already developed 1

Alternative Oral Regimens

If valacyclovir is unavailable or contraindicated, acyclovir remains effective but requires more frequent dosing:

• Acyclovir 200 mg orally 5 times daily for 5 days 3
• Acyclovir 400 mg orally 3 times daily for 5 days 3
• Acyclovir 800 mg orally 2 times daily for 5 days 3

These acyclovir regimens are less convenient due to multiple daily doses but provide similar clinical benefit when initiated early 4

Pediatric Considerations

• For patients ≥12 years old: Use the same valacyclovir regimen as adults (2 grams twice daily for 1 day) 1
• For patients <12 years old: Valacyclovir safety and efficacy have not been established; consider acyclovir dosing under specialist guidance 1

Critical Timing Considerations

The window for effective treatment is narrow:

• Initiate therapy during the prodromal phase (tingling, itching, burning sensation) before visible lesions appear 1
• Once papules, vesicles, or ulcers have formed, treatment effectiveness is significantly reduced or unproven 1
• Patients should be counseled to keep medication on hand and start immediately when symptoms begin 1

What NOT to Do: Common Pitfalls

Avoid Topical Acyclovir

• Topical acyclovir is substantially less effective than oral therapy and should not be used 3
• The systemic absorption and clinical benefit of topical formulations are inadequate for meaningful therapeutic effect 3

Do Not Delay Treatment

• Waiting until visible lesions develop eliminates the proven benefit of antiviral therapy 1
• Patients must understand that early self-initiation is essential for success 1

Avoid Inadequate Dosing

• Standard genital herpes doses (e.g., valacyclovir 500 mg) are insufficient for cold sores 1
• The high-dose regimen (2 grams) is specifically required for herpes labialis 1

Patient Counseling Points

• Valacyclovir is not a cure for cold sores; it only shortens the duration and severity of outbreaks 1
• Patients should maintain adequate hydration during treatment 1
• The virus remains latent in nerve ganglia and can reactivate, causing recurrent episodes 3, 4
• Transmission can occur through direct contact with lesions; avoid kissing or sharing utensils/drinks during active outbreaks 3
• If a dose is missed, take it as soon as remembered, but do not double the next dose 1

When to Consider Alternative Management

Frequent Recurrences

• For patients with ≥6 episodes per year, daily suppressive therapy may be considered, though this is more commonly used for genital herpes 3
• Suppressive regimens (e.g., acyclovir 400 mg twice daily) can reduce recurrence frequency by ≥75% 3

Severe or Immunocompromised Patients

• Patients with severe disease, disseminated infection, or significant immunocompromise require intravenous acyclovir 5-10 mg/kg every 8 hours 3
• Hospitalization is warranted for complications such as encephalitis or systemic involvement 3, 4

Acyclovir-Resistant Cases

• Rare in immunocompetent patients but can occur in immunocompromised hosts 3, 5
• If lesions fail to respond after 5-7 days of high-dose oral therapy, consider foscarnet 40 mg/kg IV three times daily as second-line treatment 5