Promotion Spillovers: Drug Detailing in Combination Therapy

Hongju Liu

University of Connecticut

Qiang Liu

Purdue University - Krannert School of Management

Pradeep K. Chintagunta

University of Chicago


Marketing Science, Forthcoming

This paper examines the spillover effects of promotions when products from different firms are consumed in a bundle. Using data from the HIV/AIDS category, a canonical example of combination therapy, we estimate a hierarchical Bayesian logit model across treatment regimens and show that detailing for one drug can increase demand for other drugs that are often combined with the focal drug. Such spillover effects could lead to free riding by the drugs benefitting from the spillover. We investigate the managerial and policy implications of detailing spillover effects via counterfactual policy simulations based on a dynamic oligopoly game of detailing. For managers, we show how firms can internalize the spillover effects and reduce the incentive for free riding. For policy makers, the implications of our findings relate to detailing restrictions that are often proposed on branded drugs. These restrictions aim to increase social welfare by encouraging the use of generic drugs. However, in combination therapies generic drugs may actually benefit from the detailing of complementary branded products. If detailing was curtailed, this may adversely affect prescriptions of the generic drugs as well which runs counter to policy makers’ objectives of encouraging usage of generic drugs.

Number of Pages in PDF File: 58

Keywords: pharmaceutical marketing; combination therapy; spillover; free riding; dynamic oligopoly game

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Date posted: March 8, 2014 ; Last revised: July 29, 2016

Suggested Citation

Liu, Hongju and Liu, Qiang and Chintagunta, Pradeep K., Promotion Spillovers: Drug Detailing in Combination Therapy (2016). Marketing Science, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2406363 or http://dx.doi.org/10.2139/ssrn.2406363

Contact Information

Hongju Liu (Contact Author)
University of Connecticut ( email )
2100 Hillside Rd, U-1041
Storrs, CT 06269-1063
United States
Qiang Liu
Purdue University - Krannert School of Management ( email )
1310 Krannert Building
West Lafayette, IN 47907-1310
United States
Pradeep K. Chintagunta
University of Chicago ( email )
5807 S. Woodlawn Avenue
Chicago, IL 60637
United States
773-702-8015 (Phone)
773-702-0458 (Fax)

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