Valacyclovir Dosing for Fever Blisters (Cold Sores)
The recommended dose of valacyclovir for fever blisters in immunocompetent adults and adolescents ≥12 years is 2 grams twice daily for 1 day, taken 12 hours apart, initiated at the earliest symptom (tingling, itching, or burning). 1
Treatment Regimen Details
The FDA-approved dosing is 2 grams twice daily for 1 day (total of 4 grams over 12 hours), which represents a high-dose, short-duration approach that is both convenient and highly effective. 1
This 1-day regimen reduces the median episode duration by 1.0 day compared to placebo (P = 0.001), with high-quality evidence supporting its efficacy. 2, 3
Treatment must be initiated during the prodromal phase (tingling, itching, burning) or within 24 hours of lesion onset for optimal therapeutic benefit, as peak viral titers occur in the first 24 hours. 2, 1
Alternative Dosing Options
Famciclovir 1500 mg as a single dose is an equally effective alternative with even simpler dosing. 2
Acyclovir 400 mg five times daily for 5 days is another option but requires significantly more frequent dosing and lower patient adherence. 2
The 2-day valacyclovir regimen (2 grams twice daily for 1 day, then 1 gram twice daily for 1 day) showed slightly less benefit (0.5-0.7 day reduction) and offers no advantage over the simpler 1-day regimen. 3
Critical Timing Considerations
Early initiation is essential—treatment effectiveness decreases significantly when started after lesions have fully developed. 2
Patients should be provided with a prescription to keep on hand so treatment can be initiated immediately at first symptoms. 2
Patient-initiated episodic therapy at first symptoms may even prevent lesion development in some cases. 2
Suppressive Therapy for Frequent Recurrences
For patients with ≥6 recurrences per year, consider daily suppressive therapy with valacyclovir 500 mg once daily (can increase to 1000 mg once daily for very frequent recurrences). 2
Daily suppressive therapy reduces recurrence frequency by ≥75% among patients with frequent episodes. 2, 4
Safety and efficacy have been documented for valacyclovir for 1 year of continuous use; after 1 year, consider discontinuation to reassess recurrence frequency. 2, 4
Important Clinical Considerations
Valacyclovir may be given without regard to meals. 1
Oral antiviral therapy is superior to topical treatments—topical antivirals provide only modest clinical benefit and cannot reach the site of viral reactivation. 2
The 1-day valacyclovir regimen offers greater convenience and cost benefits compared to traditional longer courses, which may improve patient adherence. 2
Common side effects include headache (<10%), nausea (<4%), and diarrhea, which are typically mild to moderate in intensity. 2
Special Populations
For immunocompromised patients, episodes are typically longer and more severe, potentially requiring higher doses or longer treatment durations. 2
Acyclovir resistance rates are higher in immunocompromised patients (7% versus <0.5% in immunocompetent patients). 2
For confirmed acyclovir-resistant HSV, IV foscarnet (40 mg/kg IV three times daily) is the treatment of choice, as all acyclovir-resistant strains are also resistant to valacyclovir. 2, 4
Common Pitfalls to Avoid
Do not rely solely on topical treatments when oral therapy is significantly more effective. 2
Do not start treatment too late—efficacy decreases substantially when treatment is initiated after lesions have fully developed. 2
Do not fail to counsel patients about trigger avoidance (UV light exposure, stress, fever, menstruation) even while on therapy. 2
Do not fail to consider suppressive therapy in patients with ≥6 recurrences per year who could significantly benefit. 2