What oral antiviral and treatment duration should be prescribed for an 80‑year‑old woman with herpes zoster, creatinine 0.94 mg/dL (estimated glomerular filtration rate ≈ 62 mL/min), and no known drug allergies?

Treatment of Herpes Zoster in an 80-Year-Old Female with Moderate Renal Impairment

For this 80-year-old woman with shingles, creatinine 0.94 mg/dL, and GFR 62 mL/min, prescribe oral valacyclovir 1 gram three times daily for 7–10 days with renal dose adjustment, or alternatively acyclovir 800 mg five times daily for 7–10 days, continuing treatment until all lesions have completely scabbed. 1, 2, 3

First-Line Antiviral Selection

Valacyclovir is the preferred first-line agent due to superior bioavailability and less frequent dosing (three times daily versus five times daily for acyclovir), which improves adherence in elderly patients. 1, 2 The standard dose for herpes zoster is 1 gram orally three times daily. 1, 2

Acyclovir 800 mg orally five times daily remains an effective alternative if valacyclovir is unavailable or not tolerated, though the more frequent dosing schedule may reduce compliance. 2, 3

Critical Renal Dose Adjustments

With a GFR of 62 mL/min (CKD stage 2), this patient requires careful monitoring but standard dosing can be used initially for valacyclovir. 1 However, given her age (80 years) and borderline renal function, close attention to nephrotoxicity is essential. 4, 5

For acyclovir at this GFR (>25 mL/min), the FDA-approved dose remains 800 mg every 4 hours, five times daily. 3 If her creatinine clearance were 10–25 mL/min, the dose would need reduction to 800 mg every 8 hours; if <10 mL/min, to 800 mg every 12 hours. 3

Important Nephrotoxicity Caveat

Elderly patients are at particular risk for acyclovir-induced renal dysfunction even with oral therapy and baseline normal renal function. 4, 5 Two case reports document irreversible chronic renal insufficiency in patients aged 76 and 78 years who received standard oral acyclovir doses for herpes zoster, despite normal baseline creatinine. 4, 5 This risk necessitates:

• Ensuring adequate hydration throughout treatment 4, 5
• Monitoring renal function at baseline and during therapy (at least once during the 7–10 day course, more frequently if any decline is detected) 1
• Considering dose reduction or extended dosing intervals if creatinine rises during treatment 3

Treatment Duration and Endpoint

Treatment must continue for a minimum of 7–10 days, but the true endpoint is complete scabbing of all lesions, not an arbitrary calendar duration. 1, 2 If lesions remain active beyond 7 days, continue antiviral therapy until all have crusted. 1, 2

Initiate treatment as soon as possible, ideally within 72 hours of rash onset, for optimal efficacy in reducing acute pain, accelerating healing, and preventing postherpetic neuralgia. 1, 2 However, treatment beyond 72 hours is still beneficial, particularly in elderly patients at high risk for complications. 1

When to Escalate to Intravenous Therapy

Switch to intravenous acyclovir 5–10 mg/kg every 8 hours if any of the following develop: 1, 2

• Disseminated herpes zoster (lesions in >3 dermatomes or visceral involvement) 1, 2
• Ophthalmic involvement with vision-threatening complications 1
• Central nervous system complications (encephalitis, meningitis) 1
• Inability to tolerate oral medications 2
• Failure to improve within 7–10 days of oral therapy 1

Monitoring Parameters

• Baseline and periodic renal function assessment (creatinine, estimated GFR) 1, 4, 5
• Daily assessment of lesion progression until all have scabbed 1, 2
• Evaluation for signs of dissemination (new dermatomes, systemic symptoms, neurological changes) 1
• Hydration status, particularly given age and renal function 4, 5

Post-Treatment Vaccination

After complete recovery, strongly recommend the recombinant zoster vaccine (Shingrix) to prevent future episodes. 1, 2 This vaccine provides >90% efficacy in preventing recurrent herpes zoster and is recommended for all adults ≥50 years regardless of prior episodes. 1, 2

Alternative Agent: Famciclovir

Famciclovir 500 mg orally three times daily for 7 days is equally effective and offers similar dosing convenience to valacyclovir. 1 For this patient's GFR of 62 mL/min, no dose adjustment is needed (standard dose applies for CrCl ≥60 mL/min). 1 However, if GFR were 40–59 mL/min, reduce to 500 mg every 12 hours; if 20–39 mL/min, reduce to 500 mg every 24 hours. 1