When Cynthia Fitzgerald started out in pharmaceutical sales 20 years ago, she received ample training on the right and wrong ways to sell medical products. Right was selling on the merits. Wrong was luring customers with perks and freebies. It was O.K. to buy doctors lunch or dinner, for example, but tempting them with lavish gifts was taboo.

"There were pretty stringent rules back then," recalls Ms. Fitzgerald, now 50 and a grandmother living in Dallas. "It was really clinically driven."

But she says those early lessons didn't serve her so well when she went to work on the other side of the table in 1998, in health care purchasing. Going by the book, and expecting her colleagues and employer to do the same, cost her a job, most of her friendships and several years of her life, she says.