Probably not what you would have guessed.
From Gina Kolata’s “Side Effects? These Drugs Have a Few.”, NYT Week in Review for June 5:
In a new paper in the Archives of Internal Medicine, Dr. [Jon] Duke [of Indiana University] and two colleagues report that the average drug label lists 70 possible side effects and some drugs list more than 500. “This was beyond even what I’d expected,” he said.
… In 2006, troubled by the ever-expanding lists of side effects, Dr. Jerry Avorn and Dr. William Shrank of Harvard Medical School wrote a paper in The New England Journal of Medicine calling it “linguistic toxicity.”
Thought these lists were getting longer? Apparently they are.