Are Physicians ÜEasy MarksÝ? Quantifying the Effects of Detailing and Sampling on New Prescriptions

Much public attention and considerable controversy surround pharmaceutical marketing practices and their impact on physicians. However, views on the matter have largely been shaped by anecdotal evidence or results from analyses with insufficient controls. Making use of a dynamic fixed-effects distributed lag regression model, we empirically assess the role that two central components of pharmaceutical marketing practices (namely, detailing and sampling) have on physician prescribing behavior. Key differentiating features of our model include its ability to (i) capture persistence in the prescribing process and decompose it into own-growth and competitive-stealing effects, (ii) estimate an unrestricted decay structure of the promotional effects over time, and (iii) control for physician-specific effects that, if not taken into account, induce biased coefficient estimates of detailing and sampling effects. Based on pooled time series cross-sectional data involving three drugs, 24 monthly observations, and 74,075 individual physicians (more than 2 million observations in total), we find that detailing and free drug samples have positive and statistically significant effects on the number of new prescriptions issued by a physician. However, we find that the magnitudes of the effects are modest.