Impact of Maine's Medicaid drug formulary change on non-Medicaid markets: spillover effects of a restrictive drug formulary.
BACKGROUND
Market penetration of HMOs affect physician practice styles for non-HMO patients.


OBJECTIVE
To study the impact of a restrictive Medicaid drug formulary on prescribing patterns for other patients, ie, so-called spillover effects.


METHODS
A before-and-after, 3-state comparison study.
On January 1, 2001, Maine's Medicaid program implemented a restrictive drug formulary for the proton pump inhibitor class, with pantoprazole as the only preferred drug.


METHODS
The Medicaid and non-Medicaid market shares of pantoprazole in Maine (vs New Hampshire and Vermont and among Maine physicians with different Medicaid share of practice.


RESULTS
After 3 months, the market share of pantoprazole in Maine (vs 2 control states) increased 79% among Medicaid prescriptions (vs 1%-2%), 10% among cash prescriptions (vs 3%), and 7% among other third-party payer prescriptions (vs 1%). The market shares increased more among Maine physicians with a higher Medicaid share of practice (high vs middle vs low [market]: 16% vs 8% vs 5% [cash]; 11% vs 5% vs 4% [other third-party payers]). Linear regression results indicate that practicing medicine in Maine leads to a 72% increase in pantoprazole share among Medicaid prescriptions (P < .001). In addition, for each 10% Medicaid share of practice in Maine, the share of pantoprazole increases 1.8% among cash prescriptions (P = .01) and 1.4% among other third-party payer prescriptions (P < .001).


CONCLUSIONS
Maine's Medicaid drug formulary generated spillover effects in cash and other third-party payer markets, with somewhat stronger effects in the cash market.
Wang
Y Richard
YR
Public Policy Department AstraZeneca Pharmaceuticals, FOC 3 CE 317, 1800 Concord Pike, Wilmington, DE 19850-5437, USA. y.richard.wang@astrazeneca.com
Pauly
Mark V
MV
Lin
Y Aileen
YA
D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D001562:Benzimidazoles / Q000191:economics / Q000627:therapeutic use*; D004363:Drug Utilization / Q000191:economics* / Q000639:trends; D004791:Enzyme Inhibitors / Q000191:economics / Q000627:therapeutic use*; D005569:Formularies as Topic; D005764:Gastroesophageal Reflux / Q000188:drug therapy*; D019981:Health Care Sector / Q000706:statistics & numerical data / Q000639:trends*; D006279:Health Maintenance Organizations / Q000191:economics*; D006801:Humans; D007356:Insurance, Pharmaceutical Services; D008281:Maine; D008484:Medicaid; D009853:Omeprazole / Q000031:analogs & derivatives; D000077402:Pantoprazole; D010818:Practice Patterns, Physicians' / Q000191:economics / Q000639:trends; D054328:Proton Pump Inhibitors; D017494:Proton Pumps / Q000145:classification / Q000191:economics; D013221:State Health Plans; D013454:Sulfoxides / Q000191:economics / Q000627:therapeutic use*; D014481:United States
D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D054328:Proton Pump Inhibitors; D017494:Proton Pumps; D013454:Sulfoxides; D000077402:Pantoprazole; D009853:Omeprazole