The U.S. Food and Drug Administration (FDA) has approved a new med to treat fibromyalgia, a mysterious disease characterized by chronic widespread pain, fatigue, sleep disturbances and depression.

The agency yesterday gave its nod to Savella (milnacipran HCL), a type of antidepressant known as a dual selective serotonin and norepinephrine reuptake inhibitor (SSNRI), according to drug makers New York City–based Forest Laboratories and Cypress Bioscience in San Diego. SSNRIs work by making it easier for neurons (nerve cells) in the brain to use the neurotransmitters serotonin and norepinephrine to send signals to one another. Both of these neurotransmitters are known to play a key role in regulating pain and mood.

Until now, only two drugs were available for treating fibromyalgia: Cymbalta made by Eli Lilly (an antidepressant and painkiller), and Pfizer's Lyrica, an Rx designed to control seizures and pain. The drugmakers said in a statement that Savella is expected to be available in U.S. pharmacies by March 2009.

According to the American College of Rheumatology, as many as 12 million people in the U.S. (4 percent of the population) suffer from fibromyalgia. The cause of this puzzling ailment is unknown, but scientists suspect genetic factors and chronic stress may be involved.

The FDA nod comes just days after a study appeared in JAMA The Journal of the American Medical Association that found that Savella and several other drugs traditionally used as antidepressants reduced some of the symptoms of fibromyalgia.

Milnacipran is approved for use as an antidepressant (called Ixel and Toledomin) in several European, Asian, and South American countries.

"It's definitely a step in the right direction, but it's not the final answer," says Rae Marie Gleason, Executive Director of the National Fibromyalgia Association, a nonprofit based in Anaheim, Calif. Gleason says that neither Savella, nor the other two drugs currently FDA-approved, work for all patients or eliminate all symptoms. Researchers should continue studying, she says "combination treatments [that integrate medication with exercise and counseling] and other medicines that might come on board."

Image credit ©iStockphoto.com/Victor Prikhodko