Acyclovir in Meningitis — Dosing by Context

1. HSV Meningitis (Adults)

• For mild–moderate HSV-2 meningitis: oral valacyclovir 500 mg TID × 7–10 days is the standard regimen.
• For severe symptoms: start with IV acyclovir (500 mg q8h) for ~3 days, then transition to oral valacyclovir.
• High-dose IV acyclovir (60 mg/kg/day in divided doses) has also been advocated, particularly where severity warrants aggressive treatment, though data are limited and no high-quality RCTs exist.
• Long-term suppressive valacyclovir (500 mg BID) did NOT reduce recurrence frequency in a randomized double-blind trial (Aurelius et al., 2012).

— Bradley and Daroff's Neurology in Clinical Practice, p. 1656–1657

2. HSV Meningitis Associated with Genital Herpes (Adults)

• IV acyclovir 5 mg/kg q8h × 5 days for severe disease or neurologic complications such as aseptic meningitis from primary genital herpes.

— Harrison's Principles of Internal Medicine 22E, p. 817

3. HSV Encephalitis / Meningoencephalitis (Adults)

• This is the standard of care for HSV encephalitis. The 21-day course is preferred to minimize relapse risk.
• Acyclovir-resistant strains: Use foscarnet 180 mg/kg/day IV in 2–3 divided doses.

— Bradley and Daroff's Neurology in Clinical Practice; The Washington Manual of Medical Therapeutics

4. Neonatal HSV Meningoencephalitis

• HSV-2 is the most common cause of neonatal CNS herpes.
• Empiric IV treatment should be started immediately if HSV is suspected.

— Bradley and Daroff's Neurology in Clinical Practice, p. 1656; The Harriet Lane Handbook 23e

5. VZV Meningitis/Encephalitis

• IV acyclovir 10–15 mg/kg q8h × 14 days is used.
• Oral valacyclovir (1 g TID) may be used in immunocompetent patients with mild disease.

Key Notes

• Renal dosing adjustment is required — acyclovir is renally cleared; reduce dose/interval with renal impairment.
• Hydration is important during IV acyclovir to prevent crystalline nephropathy.
• Enteroviral meningitis (the most common cause of viral meningitis) is treated with supportive care only — acyclovir is not indicated.
• For non-HSV viral meningitis, treatment is generally supportive.

— Washington Manual of Medical Therapeutics; Textbook of Family Medicine 9e