How should acute herpes zoster be treated in adults, including antiviral selection, dosing, and pain management?

Treatment of Acute Herpes Zoster in Adults

For uncomplicated herpes zoster, initiate oral valacyclovir 1 gram three times daily for 7-10 days within 72 hours of rash onset, continuing until all lesions have completely scabbed. 1, 2

Antiviral Selection and Dosing

First-Line Oral Therapy (Uncomplicated Disease)

Valacyclovir is the preferred first-line agent due to superior bioavailability and convenient dosing:

• Dose: 1000 mg orally three times daily for 7-10 days 1, 2
• Continue treatment until all lesions have completely scabbed, not just for an arbitrary 7-day period 1
• Most effective when started within 72 hours of rash onset, though treatment beyond this window still provides benefit 1, 3

Alternative oral options if valacyclovir is unavailable or not tolerated:

• Famciclovir: 500 mg orally three times daily for 7-10 days 1, 2
• Acyclovir: 800 mg orally five times daily for 7-10 days 1, 2, 4
  • Requires more frequent dosing, which may reduce adherence 2
  • Less favorable bioavailability compared to valacyclovir and famciclovir 1

Intravenous Therapy (Severe/Complicated Disease)

Switch to IV acyclovir for any of the following indications:

• Disseminated herpes zoster (≥3 dermatomes or visceral involvement) 1, 2
• Ophthalmic zoster with suspected CNS involvement 1
• Severely immunocompromised patients (active chemotherapy, HIV, organ transplant) 1, 2
• Inability to tolerate oral medications 2

IV acyclovir dosing:

• 10 mg/kg every 8 hours for severely immunocompromised hosts 1, 4
• 5-10 mg/kg every 8 hours for disseminated or complicated disease 1, 2
• Continue IV therapy for minimum 7-10 days and until clinical resolution (all lesions scabbed), then may switch to oral therapy 1, 2

Critical monitoring with IV acyclovir:

• Assess renal function at baseline and 1-2 times weekly during treatment 1
• Maintain adequate hydration and urine output 4
• Adjust dose for renal impairment based on creatinine clearance 1
• Monitor for thrombotic thrombocytopenic purpura/hemolytic uremic syndrome in immunocompromised patients 1

Special Population Considerations

Immunocompromised patients:

• Always treat regardless of timing from rash onset 2
• Consider temporary reduction or discontinuation of immunosuppressive medications in disseminated/invasive disease 1, 2
• May require extended treatment duration beyond 7-10 days as lesions develop over longer periods (7-14 days) and heal more slowly 1
• Higher risk of acyclovir resistance; if lesions fail to improve within 7-10 days, obtain viral culture with susceptibility testing 1

Acyclovir-resistant cases:

• Foscarnet 40 mg/kg IV every 8 hours until clinical resolution 1, 2
• Requires close monitoring of renal function and electrolytes (calcium, phosphate, magnesium, potassium) 2

Renal impairment:

• Mandatory dose adjustments for all antivirals to prevent acute renal failure 1
• Example for famciclovir: 500 mg every 8 hours if CrCl ≥60 mL/min, down to 250 mg every 24 hours if CrCl <20 mL/min 1

Pain Management

Acute Pain Control

Analgesic ladder approach:

• Mild pain: Acetaminophen or ibuprofen 1
• Moderate to severe pain: Opioid analgesics as needed during acute phase 3
• Adjunctive therapy: Gabapentin or pregabalin may be started during acute phase for severe pain 3

Topical measures:

• Apply ice or cold packs to reduce pain and swelling during acute phase 1
• Keep skin well-hydrated with emollients after lesions crust to prevent dryness and cracking 1
• Avoid topical antivirals - they are substantially less effective than systemic therapy 1, 2

Corticosteroid Considerations

Prednisone may be considered as adjunctive therapy in select cases of severe, widespread disease:

• Only in immunocompetent patients with adequate antiviral coverage 1
• Contraindicated in immunocompromised patients due to increased risk of disseminated infection 1
• Avoid in patients with poorly controlled diabetes, severe osteoporosis, or history of steroid-induced psychosis 1
• Benefits in pain reduction do not clearly outweigh risks in most patients 1

Postherpetic Neuralgia Prevention

Antiviral therapy within 72 hours of rash onset is the only proven intervention to reduce PHN risk:

• Valacyclovir and famciclovir appear superior to acyclovir for pain reduction 1
• Continue treatment until all lesions scab to optimize outcomes 1, 2

If PHN develops (pain >30 days after lesion healing):

• First-line: Gabapentin, pregabalin, or tricyclic antidepressants 3
• Second-line: Lidocaine 5% patch or capsaicin cream 3
• Third-line: Long-acting opioids or tramadol 3

Common Pitfalls to Avoid

• Do not stop treatment at exactly 7 days if lesions are still forming or have not completely scabbed 1, 2
• Do not use topical antivirals as primary therapy - they provide minimal benefit 1, 2
• Do not delay IV therapy in immunocompromised patients with facial/ophthalmic involvement 1
• Do not use corticosteroids alone without adequate antiviral coverage 1
• Do not assume treatment is futile if presenting beyond 72 hours - antiviral therapy still provides benefit for immunocompromised patients and those with ongoing new lesion formation 1, 2

Infection Control

Patients remain contagious until all lesions have crusted:

• Avoid contact with pregnant women, immunocompromised individuals, and those without varicella immunity 1
• Cover lesions with clothing or dressings 1
• Healthcare workers with active herpes zoster should be excluded from duty until all lesions crust 1

Prevention After Recovery

Recombinant zoster vaccine (Shingrix) is strongly recommended:

• For all adults ≥50 years regardless of prior herpes zoster episodes 1, 2
• Provides >90% efficacy in preventing future episodes 1
• Administer after complete recovery from acute episode 1
• Ideally given before initiating immunosuppressive therapies when possible 1