Herpes Zoster - Antiviral Therapy

Key Points

• A painful unilateral dermatomal vesicular eruption is classic for herpes zoster.
• Start oral antiviral therapy promptly, ideally within 72 hours, in patients for whom treatment is indicated.
• Ophthalmic, otic, neurologic, disseminated, or visceral disease requires urgent escalation.
• IV acyclovir is appropriate for severe disseminated or neurologic disease and selected immunocompromised patients.
• Analgesia is a core treatment because acute pain can be severe.
• Prior zoster does not eliminate the need for recommended recombinant zoster vaccination.

Algorithm

1. Confirm a dermatomal vesicular eruption and assess immune status and symptom onset.
2. Examine the eye, ear, face, and neurologic system when the distribution or symptoms suggest complications.
3. Begin oral antiviral therapy for uncomplicated high-risk disease and IV therapy for disseminated or serious complicated infection.
4. Treat pain using multimodal analgesia.
5. Obtain PCR when the diagnosis is atypical or confirmation changes management.
6. Use appropriate lesion coverage and infection-control measures.
7. Arrange urgent ophthalmology, ENT, neurology, or infectious-disease care for organ-threatening complications.

Clinical Synopsis & Reasoning

Herpes zoster typically begins with localized burning, pain, hyperesthesia, or pruritus followed by grouped vesicles on an erythematous base in one or adjacent dermatomes. Lesions usually do not cross the midline. The diagnosis is usually clinical, but PCR from a lesion is useful when morphology is atypical, the patient is immunocompromised, or confirmation will change infection-control or treatment decisions.

The key emergency question is whether disease is uncomplicated or threatens the eye, ear, central nervous system, or viscera. Vesicles on the forehead, upper eyelid, or tip of the nose suggest ophthalmic division involvement and warrant careful eye examination and urgent ophthalmology assessment when ocular symptoms or findings are present. Ear vesicles with facial weakness suggest Ramsay Hunt syndrome. Headache, neck stiffness, altered mental status, focal deficits, urinary retention, or weakness may reflect meningitis, encephalitis, myelitis, or radiculopathy. Disseminated cutaneous lesions outside the primary dermatomes are particularly concerning in immunocompromised patients.

Pain can be severe and may persist as postherpetic neuralgia after the skin heals. Risk increases with age and severity of acute pain and rash. Antiviral treatment reduces viral replication and acute disease burden, but no regimen completely eliminates the risk of chronic neuropathic pain.

Treatment Strategy & Disposition

For uncomplicated zoster, use oral valacyclovir, famciclovir, or acyclovir, ideally started within 72 hours of rash onset. Treatment remains reasonable after 72 hours when new lesions are still appearing or when the patient has high-risk disease. Dose-adjust renally. Provide scheduled nonopioid analgesia when possible, with short-term stronger analgesia or neuropathic agents for severe pain according to the clinical situation.

Use IV acyclovir for disseminated disease, severe immunocompromise with extensive infection, or serious neurologic or visceral complications. Ophthalmic disease requires systemic antiviral therapy and ophthalmology-directed management; topical ocular corticosteroids should not be started without specialist guidance. Ramsay Hunt syndrome commonly receives antiviral therapy plus corticosteroids after consideration of contraindications and specialist evaluation.

Cover active lesions and use appropriate infection-control precautions in health care settings. Avoid exposure of susceptible pregnant people, neonates, and severely immunocompromised individuals to uncovered lesions. After recovery, recommend recombinant zoster vaccination according to current age and immunocompromise recommendations because prior zoster does not guarantee future protection.

Epidemiology / Risk Factors

• Risk rises sharply with age and with impaired cell-mediated immunity.
• Vaccination has reduced the incidence and complications of zoster in vaccinated populations.
• Postherpetic neuralgia is more common in older adults.
• Disseminated and visceral disease are disproportionately seen in immunocompromised patients.

Investigations

Example Adult Dosing

Pharmacology

Prognosis / Complications

• Most uncomplicated eruptions crust and heal over several weeks.
• Postherpetic neuralgia may persist for months or longer, especially in older adults.
• Ophthalmic disease can threaten vision through keratitis, uveitis, retinitis, or elevated intraocular pressure.
• Neurologic or visceral dissemination can be life-threatening without timely treatment.

Patient Education / Counseling

• Keep lesions covered and avoid scratching.
• Explain that the virus can transmit varicella to a susceptible person through contact with active lesions.
• Seek urgent care for eye pain, visual change, facial weakness, confusion, severe headache, new weakness, or widespread lesions.
• Discuss vaccination after the acute episode according to current recommendations.
• Explain that persistent neuropathic pain after the rash heals is treatable and warrants follow-up.

Notes

Timing matters, but the 72-hour mark is not a rigid reason to withhold therapy from a patient with ongoing vesicle formation or a high-risk complication. Disease severity, immune status, and organ involvement are more important than a stopwatch alone.

Pain may outlast visible lesions because the disease affects sensory nerves. Recognizing and treating postherpetic neuralgia can substantially improve function after the acute infection resolves.

Immunocompromised patients deserve a lower threshold for admission and IV therapy because lesion count can underestimate visceral risk. Disseminated zoster is generally defined by lesions outside the primary and immediately adjacent dermatomes, but clinicians should focus on the overall distribution, host immunity, and organ symptoms rather than waiting for an arbitrary lesion count when a patient is deteriorating. In patients with facial disease, a focused cranial nerve examination can reveal subtle facial weakness, hearing change, vertigo, or dysphagia. Pain treatment should also be reassessed after the eruption crusts, because persistent burning or allodynia may need a dedicated neuropathic-pain regimen rather than repeated opioid prescriptions.

References

1. CDC: Clinical Overview of Shingles — Link
2. CDC: Shingles Vaccination — Link