Encephalitis Medication

The goals of pharmacotherapy are to reduce morbidity and prevent complications. Antivirals are used to manage treatable viral encephalitides. Corticosteroids may be considered for postinfectious or noninfectious encephalitis.

Class Summary

The goal of the use of antivirals for herpes simplex encephalitis (HSE) and varicella-zoster encephalitis is to shorten the clinical course, prevent complications, prevent the development of latency and/or subsequent recurrences, decrease transmission, and eliminate established latency.

Acyclovir (Zovirax)

Acyclovir has demonstrated inhibitory activity directed against both herpes simplex virus type 1 (HSV-1) and HSV-2, and infected cells selectively take it up.

Foscarnet (Foscavir)

Foscarnet is an organic analogue of inorganic pyrophosphate. It inhibits replication of known herpes viruses, including cytomegalovirus, CMV, HSV-1, and HSV-2. It exerts antiviral activity by inhibiting viral replication at pyrophosphate-binding sites on virus-specific DNA polymerases at concentrations that do not affect cellular DNA polymerases.

Patients who have poor clinical response or experience persistent viral excretion during therapy, especially HIV-positive patients, may be resistant to acyclovir. Patients who tolerate foscarnet may benefit from maintenance-level administration of 120 mg/kg/d early in treatment. Dosing should be individualized on the basis of the patient's renal function.

Class Summary

Corticosteroids are anti-inflammatory agents used for treatment of postinfectious encephalitis and acute disseminated encephalitis. These drugs are commonly presented as treatment alternatives, though supporting data are limited.

Dexamethasone

Dexamethasone is used to treat various allergic and inflammatory diseases. It may decrease inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Class Summary

These agents are used in patients with hydrocephalus and increased intracranial pressure (ICP) when more aggressive diuresis is desired.

Furosemide (Lasix)

Furosemide is a loop diuretic that increases excretion of water by interfering with the chloride-binding co-transport system, which, in turn, inhibits sodium and chloride reabsorption in the ascending loop of Henle and distal renal tubule. It increases renal blood flow without increasing the filtration rate. The onset of action generally is within 1 hour. It increases potassium, sodium, calcium, and magnesium excretion.

The proposed mechanism for furosemide in lowering intracranial pressure include (1) lowering cerebral sodium uptake, (2) affecting water transport into astroglial cells by inhibiting the cellular membrane cation-chloride pump, and (3) decreasing cerebrospinal fluid production by inhibiting carbonic anhydrase.

The dose must be individualized to the patient. Depending on the response, administer at increments of 20-40 mg, no sooner than 6-8 hours after the previous dose, until desired diuresis occurs. When treating infants, titrate with 1-mg/kg/dose increments until a satisfactory effect is achieved.

Mannitol (Osmitrol)

Mannitol may reduce pressure in the subarachnoid space by creating an osmotic gradient between cerebrospinal fluid in the arachnoid space and plasma. This agent is not intended for long-term use.

Initially assess for adequate renal function in adults by administering a test dose of 200 mg/kg, given IV over 3-5 minutes. This should produce a urine flow of at least 30-50 ml/h of urine over 2-3 hours.

In children, assess for adequate renal function by administering a test dose of 200 mg/kg, given IV over 3-5 minutes. This should produce a urine flow of at least 1 mL/kg over 1-3 hours.

Class Summary

These agents are used to treat seizures associated with encephalitis.

Lorazepam (Ativan)

Lorazepam is a sedative hypnotic with a short onset of effects and relatively long half-life.

By increasing the action of gamma-aminobutyric acid (GABA), which is a major inhibitory neurotransmitter in the brain, lorazepam may depress all levels of the CNS, including limbic and reticular formation.

It is important to monitor the patient's blood pressure after administering a dose. Adjust the dose as necessary.