What is the optimal treatment for acute herpes zoster in an 80‑year‑old man with normal renal function (serum creatinine 0.73 mg/dL) and good functional status?

Optimal Treatment for Herpes Zoster in an 80-Year-Old with Normal Renal Function

Oral valacyclovir 1 gram three times daily for 7 days is the optimal treatment for this patient, as his creatinine of 0.73 mg/dL and eGFR >90 mL/min indicate normal renal function requiring no dose adjustment. 1

Renal Function Assessment

This patient's renal function is entirely normal and requires no medication adjustments:

• A serum creatinine of 0.73 mg/dL in an 80-year-old man represents normal kidney function, as age-related decline in muscle mass naturally lowers creatinine production even when GFR remains preserved 2
• An eGFR >90 mL/min places this patient in Stage 1 CKD (normal kidney function), well above any threshold requiring antiviral dose modification 2
• Serum creatinine alone significantly underestimates renal function in elderly patients due to decreased muscle mass, making eGFR the more accurate assessment tool 2
• No dose adjustment for valacyclovir is required when creatinine clearance exceeds 50 mL/min, and this patient's renal function far exceeds that threshold 2, 1

First-Line Antiviral Therapy

Valacyclovir is the preferred oral antiviral for herpes zoster treatment:

• Standard dosing is valacyclovir 1 gram orally three times daily for 7 days for immunocompetent adults with herpes zoster 1
• Valacyclovir offers superior bioavailability and more convenient dosing compared to acyclovir (3 times daily vs. 5 times daily), improving adherence in elderly patients 1
• Treatment should be initiated within 72 hours of rash onset to maximize efficacy in reducing acute pain, accelerating healing, and potentially reducing postherpetic neuralgia risk 3, 4

Safety Considerations in This Patient

This patient's excellent renal function eliminates the primary safety concern with valacyclovir:

• Renal impairment is the main risk factor for valacyclovir-associated adverse effects, including neurotoxicity and acute kidney injury, but this patient's normal kidney function makes these complications unlikely 1, 5
• Common adverse effects at standard doses include headache (14%), nausea (15%), and vomiting (6%), which are generally mild and self-limited 1
• Acyclovir neurotoxicity manifests as confusion, hallucinations, and altered mental status, but occurs almost exclusively in patients with renal impairment receiving inadequately dose-adjusted therapy 5
• Monitor serum creatinine if clinical deterioration occurs, though routine monitoring is not necessary in patients with normal baseline renal function 1

Alternative Considerations

If valacyclovir is unavailable or contraindicated:

• Oral acyclovir 800 mg five times daily for 7-10 days is an acceptable alternative, though the five-times-daily dosing may reduce adherence in elderly patients 2, 1
• Intravenous acyclovir is reserved for disseminated disease, ophthalmic involvement, or immunocompromised patients, none of which apply to this case 3, 4
• Famciclovir 500 mg three times daily for 7 days is another oral alternative with similar efficacy and dosing convenience to valacyclovir 1

Critical Pitfalls to Avoid

Do not unnecessarily reduce the valacyclovir dose based on age alone:

• Age-related creatinine decline does not indicate renal impairment when eGFR remains normal, and empiric dose reduction will result in subtherapeutic antiviral levels 2
• Do not use serum creatinine as the sole marker of renal function in elderly patients; always calculate eGFR using validated equations (MDRD or Cockcroft-Gault) 2
• Do not delay treatment while awaiting laboratory confirmation if the clinical diagnosis of herpes zoster is clear, as efficacy diminishes significantly after 72 hours from rash onset 3, 4
• Do not discontinue therapy prematurely if mild gastrointestinal symptoms develop, as these are common and self-limited; only severe symptoms warrant dose adjustment or discontinuation 1