What is the treatment for Herpes (Herpes Simplex Virus) encephalitis?

Treatment of Herpes Simplex Virus Encephalitis

Intravenous acyclovir at a dose of 10 mg/kg every 8 hours for 14-21 days is the standard treatment for herpes simplex virus encephalitis and should be initiated immediately upon suspicion of the disease, without waiting for diagnostic confirmation. 1, 2

Initial Management

• Start IV acyclovir immediately upon suspicion of HSV encephalitis:

  • Adults and children >12 years: 10 mg/kg IV every 8 hours
  • Children 3 months-12 years: 500 mg/m² IV every 8 hours (minimum 21 days recommended due to higher relapse rates)
  • Neonates: 20 mg/kg IV every 8 hours 2, 3

• Treatment should ideally begin within 6 hours of admission and definitely within 48 hours of symptom onset 2

  • Mortality decreases to 8% if therapy starts within 4 days of symptom onset 1
  • Delays >48 hours between hospital admission and treatment initiation are associated with poor outcomes 2

• Do not wait for CSF PCR results before initiating treatment 1, 2

Treatment Duration and Monitoring

• Standard duration: 14-21 days of IV acyclovir 1, 2

  • Minimum 21 days for children 3 months-12 years due to higher relapse rates (up to 29%) 2
  • Shorter courses (10 days) have been associated with relapse 4

• Dose adjustments required for renal impairment based on creatinine clearance 3:

  • Monitor renal function regularly (serum creatinine, BUN)
  • Risk of nephrotoxicity increases after 4 days of therapy
  • Maintain adequate hydration to prevent crystalluria

• Perform repeat lumbar puncture with HSV PCR testing at the end of treatment to confirm resolution of infection 2

Important Clinical Considerations

• Oral acyclovir should NOT be used for HSV encephalitis as it does not achieve adequate CSF levels 2

• For patients <79 kg, a minimum dosage of 2550 mg/day (850 mg every 8 hours) may be more effective when possible 5

• Poor prognostic factors include:

  • Age >30 years
  • Low Glasgow Coma Score (<6)
  • Duration of symptoms >4 days before starting acyclovir 1
  • Persistence of confusion, aphasia, or impaired consciousness >5 days 5

• Common pitfalls to avoid:

  1. Delaying treatment while waiting for diagnostic confirmation 6
  2. Administering incorrect acyclovir dosage 6
  3. Stopping treatment based on a single negative CSF PCR, especially if taken <72 hours after symptom onset 1
  4. Using oral acyclovir instead of IV formulation 2

• Without treatment, mortality rates reach 70%, and with appropriate treatment, mortality is reduced to 20-30% 2, 7

Adjunctive Therapies

• Corticosteroids: Currently insufficient evidence for routine use in HSV encephalitis 1, 2

  • May be considered in patients with marked cerebral edema or raised intracranial pressure under specialist supervision 1
  • Results of randomized controlled trials are awaited 1

• Extended oral valacyclovir therapy after standard IV acyclovir treatment has not shown additional benefit in improving neuropsychological outcomes 2

In cases of acyclovir allergy, desensitization protocols may be considered as there are limited alternative treatment options for HSV encephalitis 8.