What is the oral dosing of antiviral medication, specifically acyclovir, for the treatment of viral meningitis?

Oral Antiviral Dosing for Viral Meningitis

Oral antivirals are not recommended for the treatment of viral meningitis, as there is no evidence supporting their efficacy for this indication. 1

Treatment Approach for Viral Meningitis

The current standard of care for viral meningitis is supportive treatment only—no antiviral therapy is indicated. 1 The UK Joint Specialist Societies explicitly state that while some clinicians treat herpes meningitis with acyclovir or valacyclovir, there is no evidence to support this practice for either HSV or VZV meningitis. 1

Key Management Principles

• Supportive care with analgesia and fluids is the mainstay of treatment for viral meningitis. 1
• Antibiotics should be stopped once viral diagnosis is confirmed, with priority given to expediting hospital discharge. 1
• CSF PCR is the gold standard for confirming viral meningitis, typically testing for enterovirus, HSV-1, HSV-2, and VZV. 1

Critical Distinction: Meningitis vs. Encephalitis

If there are ANY signs of encephalitis—including changes in personality, behavior, cognition, or altered consciousness—intravenous acyclovir must be initiated immediately. 1 This is a crucial clinical distinction:

• Viral meningitis: Normal consciousness, no cognitive changes → supportive care only 1
• Viral encephalitis: Altered mental status, personality/behavioral changes → IV acyclovir 10 mg/kg every 8 hours for 14-21 days 1

The presence of altered consciousness suggests encephalitis, not meningitis, and requires immediate IV antiviral therapy. 1, 2

Special Case: HSV-2 Meningitis

First Episode HSV-2 Meningitis

For first-episode HSV-2 meningitis specifically, the CDC recommends:

• IV acyclovir 10 mg/kg every 8 hours until resolution of fever and headache 1
• Followed by oral valacyclovir 1 gram three times daily to complete a 14-day total course 1

Recurrent HSV-2 Meningitis (Mollaret's Meningitis)

Oral valacyclovir 500 mg twice daily is NOT recommended for suppression of recurrent HSV-2 meningitis. 1 A placebo-controlled trial demonstrated that this dose did not prevent recurrent episodes and was associated with increased relapse risk after discontinuation. 1 The lack of efficacy was attributed to inadequate CSF drug levels, though higher doses have not been studied. 1

For established recurrent HSV-2 meningitis, oral therapy may be used for the entire treatment course of acute episodes. 1

Common Pitfalls to Avoid

• Do not prescribe oral antivirals for routine viral meningitis—the risks of drug side effects and prolonged hospitalization outweigh any theoretical benefit without evidence of efficacy. 1
• Do not miss encephalitis—altered mental status is the key distinguishing feature requiring immediate IV acyclovir. 1, 2
• Do not use low-dose valacyclovir for HSV-2 meningitis suppression—the 500 mg twice daily dose is ineffective and may cause rebound. 1

Summary Algorithm

1. Confirm viral meningitis diagnosis via CSF PCR and clinical presentation 1
2. Assess mental status carefully:
   • Normal consciousness → supportive care only 1
   • Any altered mental status → treat as encephalitis with IV acyclovir 1
3. For confirmed first-episode HSV-2 meningitis: Consider IV acyclovir transitioning to oral valacyclovir 1 gram TID for 14 days total 1
4. Stop antibiotics and expedite discharge once viral etiology confirmed 1