It is well known that beliefs about the quality of a drug
can enhance its physiological effect, but little is known of the impact of
advertising of a branded drug. Kamenica et al (PNAS August 2013) conducted a clinical
trial to measure the physiological impact of direct-to-consumer advertising of the
antihistamine Claritin. The authors exposed subjects with or without allergies to
a skin test of common allergens, and then subjects received Claritin, and viewed
advertisements for Claritin or Zyrtec. Regardless
of allergy, all subjects experienced a wheal reaction to the skin test. In the
allergy subpopulation, there was no significant change in beliefs associated
with exposure to Claritin advertisements; however, in the subpopulation without
allergies, exposure to Claritin advertisements increased the efficacy of
Claritin (16% at 120 minutes). This
result suggests that advertising can have strong psychologically mediated
physiological effects to a drug.
It is unclear if the
results were due to the positive effect of Claritin ads or a negative effect of
Zyrtec ads. A small pilot test included
a group that did not receive advertisements, but the authors did not replicate
this arm in the larger study. A follow
–up trial should be conducted to determine if positive or negative
advertisements have a greater effect as well as a no advertisement control
group.
