The antidepressant fluoxetine (Prozac) appears to have antiviral properties, especially against human enteroviruses — a group of more than 60 viruses that includes poliovirus.
Researchers at the University of California, Los Angeles discovered the unexpected property while conducting laboratory tests on cell cultures.
Although immunization has kept poliovirus under control around the world, other enteroviruses remain a primary cause of certain types of meningitis, encephalitis, conjunctivitis, and several other diseases.
Second only to the common cold virus, enteroviruses cause an estimated 15 million infections each year in the U.S., according to the Centers for Disease Control and Prevention.
Currently there are no treatments for enterovirus infections, and physicians can only offer supportive care and allow an infection to run its course.
An effective antiviral would be able to prevent millions of sicknesses annually, said the UCLA researchers. Vaccines are most effective if the immune system is taught to recognize and attack a virus. But enteroviruses have so much genetic variety that it would be too difficult to create a vaccine to prevent them.
So, in search for antiviral properties, the researchers turned to high-throughput screening (HTS), a method that allows scientists to test tens of thousands of chemical compounds in a single day using robotics.
The group recruited Dr. Robert Damoiseaux, the scientific director of UCLA’s Molecular Screening Shared Resource (MSSR), who specializes in HTS. Together they tested a collection of approved drugs and other chemical compounds and discovered several compounds that restrain enterovirus production.
Surprisingly, fluoxetine stood out from the crowd. In a series of follow-up tests, the researchers found that fluoxetine interferes with the growth and replication of coxsackieviruses, a prominent subtype of enteroviruses.
The researchers repeated the experiment on several kinds of coxsackieviruses with recurring success. Without the ability to reproduce, these invading viruses simply would die off.
Yet even with all this evidence, taking Prozac may not be the best way to clear a viral infection.
“We do not yet understand the mechanism of action, and we do not yet have any proof of antiviral effectiveness in humans or animals,” said lead researcher Paul Krogstad, M.D., professor of molecular and medical pharmacology.
Also, fluoxetine is linked to an increased risk of internal bleeding, and so too are some enteroviruses. The extra risk of hemorrhaging could possibly worsen the infection.
Krogstad said his group needs to gain a better understanding of how, exactly, fluoxetine stops viral reproduction. Overall, these findings could open the door to new drugs that target viral replication without the side effects of Prozac.