Wyeth ( WYE) has received conditional approval from the Food and Drug Administration for a new antidepressant, but the company didn't provide a timetable for meeting the agency's demands.

Just before markets closed on Tuesday, Wyeth said it received FDA clearance for the drug Pristiq. The main condition for final approval is Wyeth fixing problems at a plant in Puerto Rico.

The other conditions include providing more information about plans to educate doctors and patients and agreeing to conduct several post-marketing studies. No extra clinical trials are required.

The FDA's response "is in line with Wyeth's expectations, and we remain on track with our plans for Pristiq," says Joseph Mahady, a Wyeth executive. "We are working toward resolution of all outstanding issues at our manufacturing site in Guayama, Puerto Rico, and have already made significant progress in meeting previously established commitments."

Until the problems are solved, Wyeth can't make new drugs at the plant.

Analysts say Pristiq, known as DVS-233 while it was in development, could be a $1 billion-a-year treatment for depressed adults. Pristiq is a cousin of Effexor XR, and it is being counted on as the cornerstone of Wyeth's depression franchise when the older drug is hit by generic competition starting in mid-2010.

Pristiq also is being tested for several other indications. In April, Wyeth expects to hear from the FDA on its application for the drug as a treatment for symptoms of menopause.

Wyeth has been telling Wall Street that its Pristiq launch plan would depend on clinical trials involving a lower dose of the drug than were included in tests submitted to the FDA. Wyeth says these lower-dose tests, which weren't ordered by the FDA, should be evaluated early this year.

"Given the importance of Pristiq, we are committed to ensuring the most complete profile and product information is available to physicians and patients at the time of this product's launch," Mahady said.

Wyeth's stock closed up 27 cents at $51.17.