Valeant Pharmaceuticals International ( VRX) said Tuesday that it received conditional approval from the Food and Drug Administration to sell a new treatment for Parkinson's disease.

Put another way, before regulators will allow the drug to be sold, they want some type of further information.

The FDA is seeking "additional clarification on specific issues previously addressed by Valeant," the company said. "Valeant plans to meet with the FDA, promptly as they have requested, to discuss and resolve these matters."

Valeant's stock slipped as the company declined to identify the conditions set by the FDA in order for the agency to approve the drug, Zelapar. Valeant's shares fell 56 cents, or 2.8%, to $19.46.

This is the second time that the FDA has granted conditional approval for Zelapar, which is designed to work with other drugs in treating the progressive neurological disorder. In February 2003, the FDA's conditions included more safety trials when the drug was being developed by a British company called Amarin. Valeant acquired Amarin's U.S. unit last year in a deal that included the rights to Zelapar.

The drug was first submitted to the FDA in April 2002. Valeant completed the safety studies, and it resubmitted the Zelapar application in January 2005. At that time, Valeant predicted that Zelapar could reach the U.S. market by the middle of this year.

Zelapar is a faster-acting version of an existing drug, selegiline. Valeant is using a technology that allows the drug to dissolve in seconds and be absorbed in the mouth. Patients don't need to swallow or use liquid.

The delay in approving Zelapar could be related to the FDA's concerns that taking the drug with certain foods may elevate blood pressure, says Sagient Research Systems of San Diego. The firm, whose BioMedTracker report analyzes biotech issues, says selegiline tablets contain a warning about certain foods. The National Institutes of Health says such foods include liver, salami, sauerkraut, fish, poultry, yogurt, beer, red wine, avocados, bananas, figs and raisins.

"There has been some evidence that Zelapar ... has an even lower risk than selegiline, though this data may not have been enough to satisfy the FDA," a BioMedTracker report says. Sagient doesn't own shares or have a financial relationship with companies it evaluates.

At best, Zelapar could reach the market in a few months, Sagient says. "In the worst-case scenario, an additional clinical trial could be required to support efficacy or safety, which could take years," the firm says.

Zelapar belongs to a class of drugs called selective irreversible monoamine oxidase type B inhibitors, or MAO-B inhibitors.

MAO-B is an enzyme that breaks down dopamine, a chemical produced in the brain to help maintain balance and movement. When dopamine-producing cells die, people develop tremors and other neurological impairments. MAO-B inhibitor drugs try to thwart the damage caused by MAO-B enzymes, but their impact usually doesn't last very long.

Zelapar is the second MAO-B inhibitor to recently receive a conditional approval notice from the FDA. Two months ago, Teva Pharmaceutical Industries ( TEVA) got conditional clearance for Agilect.

Teva wouldn't discuss details. At the time, the company said "there remain a number of issues that Teva believed it had resolved with its submissions, but as to which the FDA continues to have concerns." Sagient Research speculates that the government agency may have raised food-related concerns about the Teva drug, too.