Acyclovir is the generic name for Zovirax, a prescription medication used to treat certain virus infections.

The Food and Drug Administration (FDA) approved acyclovir to treat viral infections from the varicella virus that causes chicken pox and shingles, as well as infections from the virus that causes genital herpes.

Sometimes doctors prescribe acyclovir to treat herpes infections in people with HIV.

The drug works by preventing viruses from dividing and multiplying. The FDA approved acyclovir in the 1980s.

Acyclovir is available as a generic, made by several companies, or under the brand name Zovirax, made by GlaxoSmithKline and available in tablet, capsule, and liquid form.

Acyclovir is one of the oldest drugs used to treat herpes simplex viruses and remains the first line of treatment for these infections.

However, research shows that acyclovir is not as effective as it used to be.

A 2013 study, published in…