Orpax was a 24th century Ferengi doctor, one of the most expensive doctors on Ferenginar. He charged two slips of latinum just to walk into the waiting room.
In 2372, he mistakenly diagnosed Quark with Dorek Syndrome, a fatal and rare disease. Orpax sent a message to Doctor Bashir that stated that Quark did not have Dorek Syndrome. Quark was overjoyed, as it meant he could sue Orpax for malpractice. (DS9: "Body Parts")
Orpax appears in the Worlds of Star Trek: Deep Space Nine third volume story "Satisfaction is not Guaranteed", where he supervises the birth of Grand Nagus Rom and Leeta's first child Bena.