To understand the influence of drug manufacturers on the prescribing patterns of medical oncologists and urologists, we examined the relationship between promotional payments from the manufacturers of abiraterone and enzalutamide and prescriptions for either drug by medical oncologists and urologists.

Promotional payments for abiraterone or enzalutamide made to medical oncologists and urologists between January 2014 and December 2017 reported through the Open Payments Program were categorized as $0, $1$999, and $1000 or more. Prescriptions filled between January 2013 and December 2017 were identified in the Medicare Part D File. Associations between promotional payments and prescribing were assessed using generalized linear models.

From 2013 through 2017, the number of medical oncologists and urologists prescribing abiraterone or enzalutamide increased by 38% – 298%, respectively. The odds of prescribing among medical oncologists receiving $1-–$999 and those receiving $1,000 or more were 1.69 (95%CI:1.59-–1.79) and 2.61 (95% CI: 2.14-–3.18) times that of medical oncologists receiving no payments. Among urologists receiving $1-–$999 and those receiving $1,000 or more, the odds of prescribing were 4.04 (95%CI: 3.59-–4.54) and 13.57 (95%CI: 9.69-–19.0) times that of urologists receiving no payments.

Increasing promotional payments were associated with prescribing among medical oncologists and urologists, with a stronger relationship evident for urologists. Prescribing patterns for abiraterone and enzalutamide, particularly among urologists, may be influenced by payments from drug manufacturers.