This paper examines the effect of direct-to-consumer advertising (DTCA) on doctor
choice of prescription drugs. Using antihistamines as an example, we show that DTCA
has a small and insignificant effect on the choice of brand despite the massive DTCA ex-
penditure incurred in this class. In contrast, direct-to-physician advertising (i.e., detailing
and medical journal advertising) has a larger and long-lasting effect on prescription choice.
These results, together with the market expanding results shown in Iizuka and Jin (2005),
support the view that DTCA is effective in increasing the number of outpatient visits per
therapeutic class but has little impact on the choice of prescription once the patient arrives
at the physician office. As a result, DTCA may be viewed as a public good for all drugs in
the same class.
