USMLE Prep - Medical Reference Library

Herpes Zoster - Antiviral Therapy

System: Dermatology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Start oral antiviral within 72 hours of rash onset or later if new lesions are appearing or eye or ear is involved; provide pain control and ophthalmology referral for ocular involvement.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Herpes Zoster Antiviral Therapy, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CBC (Baseline hematology), BMP (Electrolytes/renal). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Analgesia/Antipyretics. Use validated frameworks (e.g., Example Adult Dosing) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

Example Adult Dosing

DrugTypical course
Valacyclovir1 g three times daily for 7 days with renal adjustment
Acyclovir800 mg five times daily for 7 days with renal adjustment
Famciclovir500 mg three times daily for 7 days with renal adjustment

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
ValacyclovirDNA polymerase inhibitionHoursShingles antiviralRenal dose adjust
AnalgesicsPain controlHoursNeuropathic pain adjuncts PRNSedation

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Avoid routine systemic steroid unless directed for specific indications. Counsel regarding postherpetic neuralgia prevention measures and follow up.


References

  1. CDC - Shingles clinical overview — Link
  2. AAD - Herpes zoster guidance — Link