Converging prescription brand shares as evidence of physician learning

Within a drug category, there is an optimal brand the physician could choose to prescribe based on the patient's particular condition and characteristics. Physicians desire to prescribe the best brand for each patient for professional, moral, and legal reasons. Ideally, detailing provides information that supports this effort. This study finds that, over time, the proportion of prescriptions written for each brand moves toward a stable distribution--a convergence in which each brand's share in the category appears to match the proportion of prescription writing opportunities where the brand is the best choice for the patient. Detailing supports this convergence.