Treatment of Disseminated Herpes Simplex Virus Infection
Disseminated HSV infection requires intravenous acyclovir, not oral therapy—oral acyclovir does not achieve adequate CNS or systemic drug levels for severe disease. 1
Initial Treatment Regimen
For disseminated HSV or CNS involvement:
- Intravenous acyclovir 10 mg/kg every 8 hours for 21 days in children outside the neonatal period 1
- Intravenous acyclovir 5-10 mg/kg every 8 hours for 5-7 days or until clinical resolution for severe disseminated disease in adults 2, 3
- For neonatal disseminated or CNS disease: 20 mg/kg IV every 8 hours for 21 days 1
The higher neonatal dose (20 mg/kg vs 10 mg/kg) has decreased mortality to 5% with approximately 40% of survivors developing normally 4. This represents a critical dosing distinction based on age.
Critical Monitoring and Duration Considerations
For CNS involvement, repeat CSF HSV DNA PCR at days 19-21 of therapy; do not stop acyclovir until CSF PCR is negative 1. This is essential because:
- Relapse rates of 5-8% have been documented when therapy is stopped with positive CSF PCR 4
- A negative CSF PCR at end of therapy correlates with better outcomes 4
- If CSF remains positive, continue IV acyclovir with weekly PCR testing until negative 5
Transition to Oral Therapy
Oral acyclovir is NOT appropriate for disseminated disease during acute treatment because it does not achieve adequate CSF or systemic levels 5, 6. However, after clinical improvement with IV therapy:
- For moderate-to-severe mucocutaneous disease: Start IV acyclovir 5-10 mg/kg every 8 hours, then switch to oral acyclovir after lesions begin to regress and continue until complete healing 1
- Oral dosing after IV transition: 20 mg/kg (max 400 mg) three times daily in children <45 kg, or 400 mg twice daily in adults 1
Acyclovir-Resistant Disease
If lesions persist or progress despite appropriate acyclovir therapy, suspect resistance (particularly in immunocompromised patients):
Foscarnet 40 mg/kg IV every 8 hours OR 60 mg/kg IV every 12 hours 1
- All acyclovir-resistant strains are resistant to valacyclovir and most to famciclovir 2
- Continue until clinical resolution
- Topical cidofovir 1% may be considered for accessible lesions 2
Critical Pitfalls to Avoid
Do not use oral acyclovir for disseminated or CNS disease—it lacks adequate bioavailability for severe infections 5, 6
Do not stop therapy at 10-14 days for CNS disease—the standard is now 14-21 days minimum, with CSF PCR confirmation 4, 5, 4
Adjust for renal function—acyclovir causes crystalluria and obstructive nephropathy in up to 20% of patients, typically after 4 days of IV therapy 5, 6. Maintain adequate hydration and dose-adjust based on creatinine clearance 6
Early initiation is critical—mortality decreases from 28% to 8% when therapy starts within 4 days of symptom onset 4
Reduce immunosuppression if applicable—particularly for life-threatening or treatment-refractory disease 7
Subsequent Suppressive Therapy
After completing acute treatment for disseminated disease, consider suppressive therapy only if:
- Frequent recurrences occur (≥6 per year)
- Patient remains immunocompromised
- Dosing: 400 mg orally twice daily 6
The evidence does not support routine suppressive therapy after a single episode of disseminated disease in immunocompetent patients.