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Doctors have treated thousands of people suffering from severe depression with ketamine. It's a hallucinogenic club drug also known as Special K, and it isn't approved for treating depression. But as NPR's Jon Hamilton reports, more and more doctors are giving ketamine to patients who've run out of other options.
JON HAMILTON, BYLINE: Gerard Sanacora is a psychiatrist at Yale University who has given ketamine to hundreds of patients. As a street drug, ketamine can be dangerous, and for medical purposes, it's approved only as an anesthetic. So Sanacora says sometimes other doctors tell him...
GERARD SANACORA: This is unethical. How can you be offering this to patients based on a limited amount of information that's out there and not knowing the potential long-term risk?
HAMILTON: But Sanacora says ketamine often does something no other drug can. It relieves even suicidal depression in a matter of hours.
SANACORA: So if you have patients that are likely to seriously injure themselves or kill themselves within a short period of time and they've in fact tried the standard treatments, how do you not offer this treatment to people?
HAMILTON: More and more doctors seem to agree. Dozens of clinics in the U.S. now offer ketamine, and Sanacora says at least 3,000 patients have been treated so far. Early this month, he and other members of a task force from the American Psychiatric Association published a consensus statement on ketamine. It concludes that there is now compelling evidence that ketamine usually work even when other drugs have failed. But there are still lots of questions about ketamine. James Murrough is a psychiatrist at Mount Sinai Hospital in New York.
JAMES MURROUGH: We haven't had large-scale trials. We don't know how much or how often it should be given for it to be effective or safe.
HAMILTON: Murrough is an author of another assessment of ketamine that appears in the journal Nature Reviews Drug Discovery. He says there's an urgent need to answer questions about the drug's long-term safety because many patients require a dose every couple of weeks to keep depression at bay. Still, Murrough thinks the case for using ketamine is much stronger than it was just a few years ago.
MURROUGH: There's warranted caution that's balanced with, you know, an optimism which says we've never had a new medication for depression since the era of Prozac.
HAMILTON: Prozac arrived in the 1980s and became the first of a class of depression drugs that target the neurotransmitter serotonin. Ketamine acts on a different neurotransmitter called glutamate. And Murrough says that has got drug firms excited about the possibility of creating a whole new class of drugs for depression.
MURROUGH: Companies are reopening programs. They're pulling drugs off the shelf that they've already developed that they know act on the glutamate system.
HAMILTON: One promising candidate is a chemical sibling of ketamine called esketamine. It's now in the final phase of testing before consideration by the FDA. Yale psychiatrist Sanacora, who consults for companies developing ketamine-like drugs, says he's optimistic.
SANACORA: This is probably the most interesting and exciting new development that I've seen in my career and probably going back over the past 50, 60 years.
HAMILTON: Jon Hamilton, NPR News.
(SOUNDBITE OF BONOBO SONG, "KERALA")