To the Editor: In the enjoyable JAMA Classics discussion by Dr Evens1 regarding the 1924 article describing roentgenologic examination of the gallbladder, I spotted 1 factual error. Evens mentioned that the contrast agent used by Graham and Cole in the original study, phenolphthalein, is still marketed today under the brand name of ex-lax. Phenolphthalein was formally banned by the Food and Drug Administration as an ingredient in over-the-counter laxatives in 1999 due to concerns of possible carcinogenicity.2 Products containing phenolphthalein, including ex-lax, were reformulated in 1997 in anticipation of the ban; the active ingredient in ex-lax is now senna.
Murphy J. Movement Away From Phenolphthalein in Laxatives. JAMA. 2009;301(17):1770. doi:10.1001/jama.2009.585