Ireland's Jazz Pharmaceuticals PLC said the U.S. Food and Drug Administration's review of its narcolepsy and sleep apnea drug has been extended with a new deadline of March 20, 2019.

The FDA's original deadline to complete the review of Jazz's solriamfetol was Dec. 20. Solriamfetol is designed to improve wakefulness and reduce excessive daytime sleepiness for adults with narcolepsy and sleep apnea.

Jazz submitted new material to the FDA during review discussions, and the regulator determined that the information would require major amendments to the drug's label, resulting in a longer timeline.

The Dublin-based company's top-selling drug, Xyrem, is another treatment for narcolepsy as well as cataplexy, and it brought in sales of $357.3 million in the third quarter.