What is the dosage and treatment regimen for Valacyclovir (valacyclovir) in treating herpes simplex virus infections, including genital herpes and cold sores, as well as varicella-zoster virus infections, such as shingles?

Valacyclovir Dosage and Treatment Regimens for Herpes Virus Infections

For herpes virus infections, valacyclovir should be dosed according to the specific infection type, with 1 gram three times daily for 7 days being the standard regimen for herpes zoster (shingles), 500 mg twice daily for genital herpes recurrences, and 2 grams twice daily for one day for cold sores. 1

Dosage Recommendations by Infection Type

Herpes Zoster (Shingles)

• Standard dosage: 1 gram every 8 hours (three times daily) for 7 days 1
• Treatment should be initiated as soon as possible after diagnosis
• Dosage adjustment for renal impairment:
  • CrCl 30-49 mL/min: 1 gram every 12 hours
  • CrCl 10-29 mL/min: 1 gram every 24 hours
  • CrCl <10 mL/min: 500 mg every 24 hours 1

Genital Herpes

1. First episode:

   • 1 gram twice daily for 10 days 2

2. Recurrent episodes:

   • 500 mg twice daily for 3-5 days 1, 2
   • Treatment should be initiated at the first sign or symptom of recurrence
   • Note: Treatment initiated more than 24 hours after onset of symptoms has not been studied 1

3. Suppressive therapy:

   • Standard dosage: 1 gram once daily 1, 3
   • For patients with ≤9 recurrences per year: 500 mg once daily 1, 3
   • For immunocompromised patients (HIV-infected): 500 mg twice daily 1
   • Dosage adjustment for renal impairment required 1

Cold Sores (Herpes Labialis)

• Adults and children ≥12 years: 2 grams twice daily for 1 day (taken 12 hours apart) 1
• Treatment should be initiated at the earliest symptom (tingling, itching, or burning)
• Note: No data on effectiveness if started after development of clinical signs (papule, vesicle, or ulcer) 1

Chickenpox (Varicella)

• Children 2 to <18 years: 20 mg/kg three times daily for 5 days (maximum 1 gram three times daily) 1
• Treatment should be initiated at the earliest sign or symptom

Special Considerations

Renal Impairment

• Dosage adjustment is essential for patients with renal impairment (see table in FDA label) 1
• Hemodialysis patients should receive the recommended dose after hemodialysis 1
• About one-third of acyclovir is removed during a 4-hour hemodialysis session 1

Important Administration Guidelines

• Maintain adequate hydration during treatment 1
• If a dose is missed, take it as soon as remembered, but do not double the next dose 1
• For cold sores, treatment should not exceed 1 day (2 doses) 1

Efficacy and Safety

• Valacyclovir provides significantly better oral bioavailability than oral acyclovir, allowing for less frequent dosing 4, 5
• For herpes zoster, valacyclovir is significantly more effective than acyclovir in reducing the duration of zoster-associated pain 5
• In genital herpes, valacyclovir reduces viral shedding, hastens lesion healing, and decreases lesion-associated pain 5
• Once-daily valacyclovir (500 mg or 1 gram) is effective for suppression of recurrent genital herpes 3
• Safety profile is comparable to acyclovir and placebo in clinical trials 2, 6

Common Side Effects

• Headache (most common)
• Nausea
• Gastrointestinal complaints
• Malaise 7

Caution

• High-dose valacyclovir (8 g/day) in immunocompromised patients has been associated with thrombotic microangiopathy-like syndrome, particularly in patients with advanced HIV disease 4
• Close monitoring is indicated for immunocompromised patients receiving high-dose therapy 4

Remember that valacyclovir is not a cure for herpes infections but can effectively manage symptoms, suppress recurrences, and reduce transmission when used appropriately.