But they have disadvantages: Anti-anxiety drugs wear off quickly and are addictive. Antidepressants can take months to kick in and can have unpleasant side effects. Both must be taken for months or years, and neither addresses the underlying fear.
So far, few practitioners have used D-cycloserine on patients who were not in a study. One who has is Philadelphia psychologist Melissa Hunt, who tried the drug on a woman with a long-standing terror of driving.
The patient had tried therapy and other drugs, without success. So last year, Hunt put the woman on D-cycloserine and exposure therapy. Within a month, she was driving. "It was pretty astounding," says Hunt.
An Atlanta biotech company, Tikvah Therapeutics, is seeking FDA approval to sell D-cycloserine as an anti-anxiety medicine. Several D-cycloserine researchers, including Davis, are working with the company. This summer, Tikvah will begin a $15 million trial of the drug for social anxiety. Harold Shlevin, the company's CEO, says he hopes to get FDA approval within two to three years.
The drug is already available as a prescription antibiotic. But the FDA can grant a "new use" indication, which allows a company to sell an old drug under a different, patent-protected, name. Tikvah has an easier road than most FDA supplicants: D-cycloserine has been used for decades, so it has been proved safe - the company must show only that the drug works for anxiety.
If Tikvah does persuade the FDA, doctors wouldn't be obligated to prescribe the "new" version for psychiatric conditions. In fact, they can already prescribe D-cycloserine, or any other drug, for so-called "off-label" purposes.
But Shlevin says Tikvah's version would make the process easier because the new pills would be offered in the lower doses used for anxiety. He said he doesn't know how much his version might cost compared with generic D-cycloserine.
D-cycloserine might have other uses, too. Scientists at Northwestern have found that in rats, it reduces pain.
"If you give [D-cycloserine] for a few weeks, it starts acting as an analgesic," says Northwestern researcher A. Vania Apkarian, who led the study. Intriguingly, D-cycloserine's effect lasted for weeks after the animals stopped getting it - other pain relievers stop working within hours or days. When the rats started up again, the drug became more effective.
"The longer you use it, the better subjects get," says Apkarian. He thinks the drug modifies cortical structure. "We think we are reorganizing the connectivity of the brain," he says.
In recent studies, Apkarian has shown that the brains of people in chronic pain continue to transmit heightened pain signals even after the actual stimulus stops. Their pain-sensing apparatus gets stuck in the "on" position. In these people, brain areas that block pain actually shrink.
Apkarian suspects that D-cycloserine helps these regions regenerate, allowing them to properly dampen pain again. He will soon begin a study to test the theory on patients with chronic back pain.
"We certainly expect that this drug will make chronic pain patients feel better. That possibility does not really exist now," he says. "If D-cycloserine does the same thing in humans as it does in rats, it will have huge effects."
david.kohn@baltsun.com
