"We feel it is a better use of resources to use fewer speakers more often. This cuts down on training costs as well as lessens the number of contracts needed," she wrote in an email.
Some companies also have replaced some in-person speaking events with teleconferences, webcasts and video conferences.
"It's really unclear how much money is being spent in any one of these areas," said Vincent DeChellis, a principal at NHHS Healthcare Consulting, which has studied the data.
Scrutiny of speaker programs has prompted changes. After ProPublica reported last year that state medical boards had sanctioned some drug-company speakers, the firms pledged to toughen their screening procedures and exclude physicians with disciplinary records.
Separately, ProPublica found that universities were not enforcing their own policies barring physicians from giving promotional speeches. In response, a number of schools said they would begin using the payment rosters to check for rule-breakers.
Pharma's trade group said the focus of most companies right now is ensuring the accuracy of data that will be publicly released in 2013. But this information also must be put into context for patients, said Diane Bieri, executive vice president and general counsel for the Pharmaceutical Research and Manufacturers of America.
Doctors help develop new medicines, advise companies on marketing and help educate their peers about appropriate uses of new drugs, she said.
"If the only information that's available is that company A paid doctor B $75,000 for a consulting arrangement," she said, "that's typically not enough information to really educate the patient about what was involved in that relationship."
Tribune reporters Judith Graham and Brian Boyer contributed.