Health Library Acyclovir for EncephalitisFrom Healthwise

Acyclovir prevents herpes simplex virus—the virus that causes chickenpox, cold sores, and genital herpes—from reproducing. The medicine is given in a vein (intravenous, or IV) when used to treat encephalitis caused by these viruses.

Acyclovir is used to treat encephalitis caused by herpes simplex and varicella-zoster.

To improve the chance of survival from herpes simplex encephalitis, acyclovir should be given as soon as the illness is diagnosed. The death rate from this form of encephalitis is less than 30% when prompt treatment is given, compared with 70% to 80% without treatment.¹

The main factors that affect the success of treatment include the age of the person and his or her level of consciousness. Confusion and disorientation (altered consciousness) are signs of encephalitis. People under age 30 and those who have a normal level of consciousness have better results than people over 30 and those who have altered consciousness.²

The length of the illness also is important. In people who had the disease for 4 days or less, survival increased from 65% to 100% in those people who got acyclovir treatment.³ But even with treatment, serious mental and physical impairments can occur, such as paralysis, seizures, or hearing loss.

Side effects of intravenous acyclovir include:

• Inflammation at the injection site.
• Short-term increase in the creatinine level in the blood.
• Nausea and vomiting.
• Itching, rash, or hives.
• Anemia.
• Lightheadedness.
• Headache.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

Valacyclovir, penciclovir, and famciclovir are approved by the U.S. Food and Drug Administration (FDA) for herpes zoster treatment. They are being studied as a treatment for herpes simplex encephalitis. Some doctors are now using these medicines for this purpose as an unlabeled use.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.

Citations

1. Jubelt B (2005). Viral infections. In LP Rowland, ed., Merritt's Neurology, 11th ed., chap. 24, pp. 175–210. Philadelphia: Lippincott Williams and Wilkins.
2. Roos KL, Tyler KL (2008). Meningitis, encephalitis, brain abscess, and empyema. In AS Fauci et al., eds, Harrison's Principles of Internal Medicine, 17th ed., vol. 2, pp. 2621–2641. New York: McGraw-Hill.
3. Whitley RJ, Gnann JW (2002). Viral encephalitis: Familiar infections and emerging pathogens. Lancet, 359: 507–514.

Author:	Monica Rhodes	Last Updated: August 5, 2008
Medical Review:	E. Gregory Thompson, MD - Internal Medicine W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
© 1995-2010 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.