We estimate a sales response model to evaluate the short- and long-term value of a sales representative’s detailing visit to different types of physicians. By understanding the dynamic effect of sales calls across heterogeneous physicians, we provide guidance on the design of optimal call patterns in route sales. Our analyses reveal that the long-term persistence effect of detailing is more pronounced for specialist physicians, whereas the contemporaneous marginal effect is higher for generalists. We also provide a key methodological insight to the marketing and economics literature. We show that in the Nerlove-Arrow framework, moment conditions typically used in conventional dynamic panel data methods become vulnerable to serial correlation in the error structure. We discuss the associated biases and present a robust set of moment conditions for both lagged dependent and predetermined explanatory variables in estimation. Furthermore, we show that conventional tests to detect serial correlation have weak power and can be misleading, resulting in a misuse of moment conditions, which leads to incorrect inference. We provide theoretical illustrations and Monte Carlo simulations to validate our claims.