Viral encephalitis

Antimicrobial prescribing: NHS Lothian
NHS Lothian

Patients with suspected viral encephalitis should be commenced on Aciclovir based on presentation, initial CSF results and imaging findings without waiting for CSF PCR results.

HSV encephalitis

Treatment recommendation: 

Treatment is IV.  Oral therapy is not appropriate.

Aciclovir 10mg/kg every 8 hours IV  (See below to calculate dose)

Calculate IV Aciclovir dose:

- Ensure up to date weight and height are obtained.

- Calculate renal function. Dosage adjustments are required if CrCl<50ml/min - see BNF. Dosing interval may need adjusting during treatment if renal function improves/ deteriorates

- Use Adjusted Body Weight equation to calculate weight (kg) for obese patients (BMI ≥ 30 kg/m2):

Adjusted body weight = (0.4 x [total body weight – ideal body weight]) + ideal body weight.

Ideal body weight can be obtained from Ideal Body Weight Chart

- Where possible, double check your calculations with the ward pharmacist before prescribing.

- Ensure appropriate hydration, close monitoring renal function and clinical response.

 

Recommended duration

Discuss with virology/ infection specialist

Suggestion:

If immunocompetent: usually repeat LP at day 13-14 to guide a decision about treatment on day 14.

  • If repeat CSF HSV PCR negative: stop treatment at day 14
  • If repeat CSF HSV PCR positive: aciclovir should be continued for a further 7 days, with weekly HSV PCR on CSF until negative.

If immunocompromised: usually 21 days with repeat CSF PCR testing at day 20-21 to decide on further management.

Other causes of viral encephalitis

Cases of VZV encephalitis should be discussed with virology/infection specialist.   

There are lots of rarer causes of viral encephalitis. Patients with suspected or proven viral encephalitis of other aetiologies should be discussed with virology/infection specialist.