NEW YORK (AP) — Shares of Discovery Laboratories Inc. plunged today after the company said the launch of its respiratory drug Surfaxin will be delayed about six more months, to the fourth quarter of 2013.

Discovery Labs said the Food and Drug Administration asked it to provide more information about the way it documents Surfaxin product specifications and a new analytical chemistry method. The Warrington, Pa., company said it will respond to the FDA within two months, and the agency will have up to four months to review the new submissions. If the review is successful, Discovery Labs said it would start marketing Surfaxin during the fourth quarter.

The company’s stock declined 40 cents, or 16.7 percent, to $1.99 in midday trading.

Surfaxin is intended to prevent a condition called respiratory distress syndrome in premature infants. Respiratory distress syndrome occurs when children are born without enough pulmonary surfactant, a substance produced by the lungs that is essential for breathing. The condition is often treated with mechanical ventilation and animal-derived surfactant replacements.

The FDA approved Surfaxin in March 2012, and at the time, Discovery Labs said it would start marketing the drug during the fourth quarter of the year. But in October, the company said it had to update product specifications and one of the ways it measured the performance of Surfaxin. Discovery Labs said that would delay the launch of Surfaxin to the second quarter of 2013.