From the Guidelines
Acyclovir Dose for CNS Coverage
The recommended dose of Acyclovir for central nervous system (CNS) coverage is 10 mg/kg intravenously every 8 hours for patients with normal renal function 1.
Important Considerations
- The dose should be reduced in patients with pre-existing renal impairment 1.
- For neonates, a higher dose of 20 mg/kg intravenously every 8 hours is recommended 1.
- The treatment duration is typically 14-21 days 1.
- It is essential to start Acyclovir therapy as soon as possible, pending diagnostic study results, to improve outcomes in patients with suspected encephalitis 1.
Specific Patient Populations
- For children between 3 months and 12 years, the dose is 500mg/m2 8 hourly 1.
- For patients over 12 years, the dose is 10mg/kg 8 hourly 1.
- In immunocompromised patients with VZV encephalitis, a prolonged course of intravenous Acyclovir may be needed 1.
From the FDA Drug Label
Concentrations achieved in the cerebrospinal fluid are approximately 50% of plasma values. The only major urinary metabolite detected is 9-carboxymethoxymethylguanine accounting for up to 14.1% of the dose in patients with normal renal function. Herpes Simplex Encephalitis Sixty-two patients ages 6 months to 79 years with brain biopsy-proven herpes simplex encephalitis were randomized to receive either acyclovir (10 mg/kg every 8 hours) or vidarabine (15 mg/kg/day) for 10 days
The Acyclovir dose for central nervous system (CNS) coverage is 10 mg/kg every 8 hours for the treatment of herpes simplex encephalitis, as it achieves approximately 50% of plasma concentrations in the cerebrospinal fluid 2.
From the Research
Acyclovir Dosing for CNS Coverage
- The ideal dose of acyclovir for central nervous system (CNS) coverage is not explicitly stated in the provided studies 3, 4, 5, 6, 7.
- However, it is mentioned that high doses of acyclovir are associated with increased concentrations of acyclovir and its metabolite 9-carboxymethoxymethylguanine (CMMG) in the cerebrospinal fluid (CSF) 3.
- A study from 2017 reported the use of high-dose oral valacyclovir (3 g daily) as an alternative to intravenous acyclovir during a shortage, with tolerable adverse effects 5.
- Another study from 2015 emphasized the importance of adequate hydration (more than 2 L/day) to prevent nephropathy in patients receiving intravenous acyclovir for suspected herpes simplex virus (HSV) infection 6.
- The relationship between acyclovir concentrations and neurotoxicity is complex, with a delay of 24 to 48 hours between peak serum concentrations and the development of CNS symptoms 7.
Key Considerations
- Renal function and hydration status should be carefully monitored in patients receiving acyclovir for CNS infections 3, 6.
- The use of high-dose acyclovir or valacyclovir should be approached with caution, considering the potential for increased toxicity 3, 5.
- Further research is needed to determine the optimal dosing regimen for acyclovir in patients with CNS infections, taking into account individual factors such as renal function and hydration status 3, 4, 5, 6, 7.