Determinants of generic vs. brand drug choice: evidence from population-wide Danish data.

We investigate if demand for branded prescription medications in post-patent markets is patient- or doctor driven. When drugs go off-patent the brand medication often maintains non-negligible market shares. We use population-wide Danish data including all prescriptions for seven blockbuster drugs from 1998 to 2008, which amounts to 13,415,012 prescriptions. At the outset, descriptive statistics suggest large variation in drug choice over doctors. Nonetheless, using a two-way fixed effects model we find that the primary determinants of brand drug use are unobserved patient characteristics and price effects.