The U.S. Food and Drug Administration announced it is requiring manufacturers to put a boxed warning on the prescribing information for the smoking cessation drugs Chantix (varenicline) and Zyban (buproprion). The warning will highlight the risk of serious mental health events including changes in behavior, depressed mood, hostility, and suicidal thoughts when taking these drugs.

Similar information on mental health events will be required for buproprion marketed as the antidepressant Wellbutrin and for generic versions of buproprion. (These drugs already carry a boxed warning for suicidal behavior in treating psychiatric disorders.)

FDA analyses revealed that some who have taken Chantix and Zyban have reported experiencing unusual changes in behavior, become depressed, or had their depression worsen, and had thoughts of suicide or dying. In many cases, the problems began shortly after starting the medication and ended when the medication was stopped. However, some people continued to have symptoms after stopping the medication.

Neither Chantix nor Zyban contain nicotine and some of these symptoms may be a response to nicotine withdrawal.