Are Physicians "Easy Marks"? Quantifying the Effects of Detailing and Sampling on New Prescriptions

While much public attention and considerable controversy surround pharmaceutical marketing practices and their impact on physicians, 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 competitivestealing effects, (ii) estimate an unrestricted decay structure of the promotional effects over time, and (iii) control for physician-specific effects which, if not taken into account, induce biased coefficient estimates of detailing and sampling effects. Based on pooled time series cross-sectional data involving 3 drugs, 24 monthly observations and 74,075 individual physicians (over 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, contrary to the dominant views in the public policy debate and the results of earlier studies, we find that the magnitudes of the effects range from modest to very small. Rather than being “easy marks,” our findings are consistent with physicians being “tough sells.”