MATTHEW PERRONEWASHINGTON (AP) ¿ New labels on popular asthma drugs like Merck's Singulair must highlight language about suicidal behavior, depression and anxiety seen in a small number of patients, federal regulators said Friday. After 15 months of investigation, the Food and Drug Administration said Merck & Co. Inc., AstraZeneca and Cornerstone Therapeutics will have to raise label warnings about psychiatric problems reported by a handful of patients taking their drugs. "Patients and healthcare professionals should be aware of the potential for neuropsychiatric events with these medications," the FDA said in a posting to its Web site. A spokeswoman for Merck said the language already appears in Singulair's label, but will be raised to the "precautions" section. It's now listed in a section about various side effects reported by patients. "We've been working with the FDA since Singulair came to market and every time we update the label it's in cooperation with them," said Merck spokeswoman Pamela Eisele. Singulair was Whitehouse Station, N.J.-based Merck's best-selling product last year, with U.S. sales of $3.5 billion.