Valacyclovir Dosing for Herpes Zoster (Shingles)
For immunocompetent adults with herpes zoster, prescribe valacyclovir 1000 mg orally three times daily for 7 days, starting within 72 hours of rash onset, and continue treatment until all lesions have completely scabbed. 1
Standard Dosing for Immunocompetent Adults
Valacyclovir 1000 mg three times daily for 7 days is the established first-line regimen for uncomplicated herpes zoster in immunocompetent adults. 1, 2
Initiate therapy within 72 hours of rash onset to achieve maximal benefit in reducing acute pain, accelerating lesion healing, and preventing postherpetic neuralgia. 1, 3
Continue treatment until all lesions have fully scabbed, rather than stopping at exactly 7 days if active vesicles remain. 1, 3
Valacyclovir offers superior bioavailability compared to acyclovir and requires only three-times-daily dosing versus five-times-daily for acyclovir 800 mg, improving adherence. 4, 5
Compared with acyclovir, valacyclovir shortens the duration of acute zoster pain and reduces the incidence of postherpetic neuralgia—the median pain duration was 38 days with valacyclovir versus 51 days with acyclovir in patients ≥50 years. 1, 4
Immunocompromised Patients
For immunocompromised adults with uncomplicated herpes zoster, use acyclovir 800 mg orally four times daily instead of high-dose valacyclovir, because valacyclovir doses ≥8 g/day carry a risk of thrombotic thrombocytopenic purpura/hemolytic-uremic syndrome (TTP/HUS). 1
For severe disease, disseminated infection, or complications (pneumonitis, hepatitis, CNS involvement) in immunocompromised patients, administer intravenous acyclovir 10 mg/kg every 8 hours for 7–10 days or longer until all lesions have scabbed. 1, 3
Temporarily reduce or discontinue immunosuppressive medications when clinically feasible to aid recovery in disseminated or invasive herpes zoster. 1, 3
In a double-blind study of immunocompromised patients, both valacyclovir 1 g three times daily and 2 g three times daily demonstrated similar median times to full crusting (8 days) and were equally safe and effective for reducing zoster-associated pain. 6
Renal Dose Adjustments
All patients with impaired renal function require dose reduction based on creatinine clearance to prevent neurotoxicity and nephrotoxicity. 1, 2
| Creatinine Clearance | Adjusted Valacyclovir Dose for Herpes Zoster |
|---|---|
| 30–49 mL/min | 1000 mg every 12 hours [1,2] |
| 10–29 mL/min | 1000 mg every 24 hours [1,2] |
| <10 mL/min | 500 mg every 24 hours [1,2] |
Hemodialysis patients should receive the recommended dose after each hemodialysis session, as approximately one-third of acyclovir is removed during a 4-hour session. 2
Peritoneal dialysis patients do not require supplemental dosing beyond the adjustments for creatinine clearance <10 mL/min. 2
Assess baseline renal function before initiating therapy; during intravenous acyclovir, monitor renal function once or twice weekly. 1, 3
Maintain adequate hydration throughout antiviral therapy to minimize nephrotoxicity. 1
Pediatric Dosing
Adolescents ≥12 years who can tolerate adult dosing should receive valacyclovir 1000 mg three times daily for 7 days. 1
Children <12 years are treated with acyclovir 20 mg/kg orally four times daily (maximum 800 mg per dose) for herpes zoster. 1
Critical Pitfalls to Avoid
Do not use topical acyclovir alone—it is substantially less effective than systemic therapy for herpes zoster. 1, 3
Do not use short-course (1–3 day) regimens designed for genital herpes; these are inadequate for treating herpes zoster. 1
Avoid valacyclovir doses of 8 g/day in immunocompromised patients due to TTP/HUS risk. 1
Do not delay antiviral initiation while awaiting laboratory confirmation; start treatment based on clinical presentation within 72 hours of rash onset. 1, 3
Treatment Failure and Antiviral Resistance
If herpes zoster lesions do not begin to resolve within 7–10 days of appropriate valacyclovir therapy, suspect antiviral resistance and obtain a viral culture with susceptibility testing. 1
All acyclovir-resistant strains are also resistant to valacyclovir. 1, 7
For confirmed resistant VZV, treat with intravenous foscarnet 40 mg/kg every 8 hours until clinical resolution. 1, 3
Resistance rates are <0.5% in immunocompetent patients and 5–7% in immunocompromised patients. 1