For a half-century, D-cycloserine has led a quiet, workmanlike existence as an antibiotic, primarily for tuberculosis in developing countries. Its patent has long since expired, and its popularity has waned as newer antibiotics have appeared.
But D-cycloserine might now get a second act: A growing number of researchers say the drug could transform the way doctors treat a range of psychiatric ailments, including anxiety, phobia and obsessive-compulsive disorder. It could also help alleviate addiction, post-traumatic stress disorder, depression and chronic pain.
The drug has become a hot topic in anxiety research, with about 30 studies now under way. And a biotech company is seeking approval from the Food and Drug Administration to use D-cycloserine for anxiety disorders.
"It's a very exciting treatment, and it holds great promise," says Michael Otto, director of the Center for Anxiety and Related Disorders at Boston University. "It gives us a whole new direction to go in."
Otto, who has studied the drug's effect on panic and obsessive-compulsive disorders (it worked on both), says the field needs new approaches. More than 40 million Americans suffer from anxiety disorders, according to the National Institutes of Mental Health. Only a third get treatment, and only half of those are satisfied with the results.
The drug could offer significant improvements over current anti-anxiety medicines, which must be taken for months or years. D-cycloserine, by contrast, requires just a few doses.
The drug was introduced in 1955. Now made by Eli Lilly, it's used mostly in the developing world - in part because it's less expensive than newer antibiotics.
In the mid-1990s, Emory University neuroscientist Michael Davis became fascinated with D-cycloserine. He had been studying how certain compounds in the brain produce intense, long-lasting anxiety. In particular, he focused on a chemical receiving station called the N-methyl-D-aspartic acid (NMDA) receptor, which seems to play a key role in the process of acquiring - and losing - fears.
For years, researchers had known that D-cycloserine can do more than kill bacteria: It increases the activity of NMDA. Davis began experiments on rats and found that animals given a combination of training and D-cycloserine lost their fears more often, and more quickly, than those that received training alone.
