NEW YORK (CNNMoney.com) - Antidepressants in the form of a patch, not a pill, will soon line pharmacy shelves.

The Food and Drug Administration gave the green light Tuesday to the first-ever antidepressant patch. It comes from a partnership of drug makers: Bristol-Myers Squibb (unchanged at $23.10, Research), which is marketing the drug in the U.S., and Somerset Pharmaceuticals, a drug development company jointly held by Mylan Laboratories (unchanged at $23.00, Research) and Watson Pharmaceuticals (unchanged at $29.98, Research).

The patch, called EMSAM, delivers an antidepressant called selegiline through the skin, or transdermally. Unlike other antidepressants, the drug is not absorbed through the digestive tract, and it is intended for patients with major depressive disorder, or MDD, who have failed other treatments. MDD is a severe form of depression with an increased risk of suicide, according to the National Institutes of Health.

"Essentially, the most positive point is that through transdermal delivery you are going directly into the blood stream," Bristol-Myers spokesman Craig Stoltz said. "It gives physicians another option, an important option, for patients with MDD."

Stoltz said that EMSAM is a member of a drug class called monoamine oxidase inhibitors, which can lead to hypertension if absorbed through the stomach. The 24-hour patch releases a constant stream of selegiline into the blood, and the patch is replaced every day. The drug will become available in late April, Stoltz said, and should never be combined with another antidepressant.

Spokespeople for New York City-based Bristol-Myers and Tampa-based Somerset would not provide sales projections. David Moskowitz, analyst for Friedman, Billings & Ramsey, projected sales of $83 million by 2009 and said profits would be split among the companies. Moskowitz estimated the antidepressant market to be $12 billion.

These projected sales are relatively slim for a company like Bristol-Myers, which totaled nearly $20 billion in 2005 sales, with its lead product Plavix, an anti-clotting drug, totaling $3.8 billion.

But Moskowitz said EMSAM profits won't be hampered by too much overhead, because Bristol-Myers already has a sales staff focused on psychiatric drugs like Abilify, the treatment for bipolar disorder and schizophrenia that totaled $912 million in 2005 sales. He said the Bristol-Myers sales staff can be easily and inexpensively adapted to sell EMSAM while also selling Abilify to psychiatrists.

The EMSAM "starter dose" of 6 milligrams would not require diet changes in patients, said Stoltz of Bristol-Myers, but higher doses would. Moskowitz of FBR said this probably would not dissuade psychiatrists from prescribing the drug.

"Our assumption is that psychiatrists are going to be cautious with this product, but when they're dealing with severe or treatment-resistant depression, we believe that they will turn to this option," Moskowitz said.

Moskowitz does not own shares of Bristol-Myers stock.

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To see the 2006 outlook for antidepressants, click here.