Sriram Venkataraman of Emory University in Atlanta and Stefan Stremersch of Duke University in Durham, N.C., said that debate is mounting on the role of influencers such as patient requests in physician decision making, both on prescriptions and sample dispensing.

Their study, published in Management Science, found marketing efforts -- operationalized as detailing and symposium meetings of firms to physicians -- and patient requests do affect physician decision making differentially across brands.

However, the study of pharmaceutical companies' marketing to physicians also showed that doctors are most influenced by brand preference and marketing that addresses the problems of drugs with many side effects.

In addition, the researchers found the responsiveness of physicians' decision making to marketing efforts and patient requests depends upon the drug's effectiveness and side effects.