What is the comparison between Acyclovir (antiviral medication) and Valacyclovir (valacyclovir hydrochloride) for the treatment of Herpes Labialis (cold sores)?

From the Guidelines

Valacyclovir is the preferred treatment for cold sores due to its better bioavailability and more convenient dosing schedule, as evidenced by the most recent study 1.

Key Points to Consider

• Valacyclovir is a prodrug of acyclovir, meaning it converts to acyclovir in the body but achieves higher blood levels with fewer doses, leading to better effectiveness and convenience 1.
• For cold sores, valacyclovir is typically prescribed as 2 grams taken twice daily for one day (doses separated by 12 hours), while acyclovir requires more frequent dosing at 400 mg five times daily for five days.
• Both medications work by inhibiting viral DNA synthesis, preventing the herpes simplex virus from replicating, and should be started at the first sign of a cold sore (tingling or burning sensation) for maximum effectiveness.
• Side effects are generally mild for both medications and may include headache, nausea, or dizziness, with people with kidney problems potentially needing dose adjustments for either medication 1.
• The convenience of valacyclovir's dosing schedule often outweighs its typically higher cost compared to acyclovir, especially considering the importance of treatment adherence.

Clinical Considerations

• Patient education on the importance of initiating treatment during the prodrome phase is crucial for effective management of cold sores 1.
• Pharmacists play a significant role in advising patients on the correct use of antiviral medications for cold sores, including considerations for dosing, potential interactions, and the need for medical evaluation if symptoms persist or worsen.
• The move towards making antiviral medications for cold sores available over-the-counter (OTC) in some regions highlights the need for clear patient education and pharmacist guidance to ensure appropriate use and minimize risks 1.

From the FDA Drug Label

1 INDICATIONS AND USAGE 1.1 Adult Patients Cold Sores (Herpes Labialis) VALTREX is indicated for treatment of cold sores (herpes labialis).

The efficacy of VALTREX initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer) has not been established.

The FDA drug label does not answer the question.

From the Research

Comparison of Acyclovir and Valacyclovir for Cold Sores

• Valacyclovir is better absorbed than acyclovir, increasing acyclovir bioavailability three- to fivefold 2.
• High-dose, short-duration, early valacyclovir therapy has been shown to be effective in the treatment of cold sores, reducing the median duration of the episode by 1.0 day and the mean duration of the episode by 1.1 days compared to placebo 2.
• Valacyclovir has been found to be safe and effective in the treatment of cold sores, with a 1-day treatment regimen offering a unique and convenient dosing alternative compared to available topical therapies 2, 3.

Efficacy of Valacyclovir

• Valacyclovir has been shown to increase the proportion of subjects whose cold sores were aborted and decrease healing times for subjects with cold sore lesions compared to placebo 3.
• The use of valacyclovir has been found to be effective in reducing the duration of cold sore episodes and preventing lesion development 2, 3.

Prescription Trends

• Valacyclovir and acyclovir are the most commonly prescribed medications for cold sores, with valacyclovir use increasing and acyclovir use decreasing over time 4.
• Physicians may be evolving their treatment strategies to implement newer antiviral medications, such as valacyclovir, which may be more efficacious for the treatment of cold sores 4.

Pharmacology and Clinical Efficacy

• Valacyclovir is a highly bioavailable prodrug of acyclovir, with a higher bioavailability than acyclovir 5.
• Valacyclovir has been found to be safe and effective in the therapy of patients with herpes simplex and herpes zoster, and may be useful in other viral infections 5, 6.