The FDA wants Pfizer (the manufacturer of Chantix) and GlaxoSmithKline, (the maker of another commonly prescribed smoking cessation drug, Zyban), to amplify warnings about the serious reactions users of the drugs may experience. The agency announced today that it would require the drug companies to put boxed warnings on product labeling for Chantix and Zyban. Zyban (bupropion hydrochloride) is also marketed as Wellbutrin when prescribed as an antidepressant.