What Is Acyclovir? - Uses & Side Effects

Instructor: Kara Jones
Acyclovir is one of many drugs used to treat viral infections. Explore the different ways this drug is used to treat viruses, and read about the common side effects.

What is a Virus?

Have you ever had a cold that seemed impossible to shake? If so, a virus was to blame. Viruses are pesky little organisms that can only survive and reproduce by infecting a living host. Although the human body is the most common host, animals, plants, and even other organisms can contract viruses as well.

Viruses spread by entering normal, healthy cells in a host and taking over the part of the cell that controls replication. Once that happens, they can reproduce inside the cell. When the cell gets full of these 'baby' viruses, it bursts. This releases the baby viruses into the bloodstream, where they look for the next available cell to infect. At this point the whole cycle starts over again.

Viruses are not the same as bacteria and cannot be treated with antibiotics. Viruses also tend to mutate. This means they can adapt to the environment and change how much they can damage the host. A common example of a virus is the rhinovirus -- otherwise known as the common cold. There are currently over 31,000 strains of rhinovirus in the world today. One other important thing to know: viruses can't be cured, so this limits the types of treatment available.


Acyclovir is an antiviral drug. It is used to prevent or slow down the spread of a viral infection. It works by stopping the virus's connection to the replication process of the cell. It works very well against herpes simplex 1 (cold sores), herpes simplex (genital herpes), herpes zoster virus (shingles), and the cytomegalovirus (also known as CMV).

Acyclovir can be taken by mouth, but is also available in an injectable form that can be given directly into a vein for more serious cases. Remember, acyclovir doesn't offer a cure, but does help reduce how often symptoms occur and how severe they are. It also does not prevent the spread of a virus from person to person.

Herpes simplex virus

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