At night, a drug firm gets the last word: A promo for the heart drug Multaq stood on each doctor’s nightstand Wednesday.

Who arranged this commercial barrage? The society itself, which sold access to its members and their purchasing power.

Last year’s four-day event brought in more than $5 million, including money for exhibit booths the size of mansions and company-sponsored events. This year, there are even more “promotional opportunities,” as the society describes them.

Concerns about the influence of industry money have prompted universities such as Stanford and the University of Colorado-Denver to ban drug sales representatives from the halls of their hospitals and bar doctors from paid promotional speaking.

Yet, one area of medicine still welcomes the largesse: societies that represent specialists. It’s a relationship largely hidden from public view, said David Rothman, who studies conflicts of interest in medicine as director of the Center on Medicine as a Profession at Columbia University.

Professional groups such as the Heart Rhythm Society are a logical target for the makers of drugs and medical devices. They set national guidelines for patient treatments, lobby Congress about Medicare reimbursement issues, research funding and disease awareness, and are important sources of treatment information for the public.

Dozens of such groups nationwide encompass every medical specialty from orthopedics to hypertension.