The impact of generic-only drug benefits on patients' use of inhaled corticosteroids in a Medicare population with asthma.
BACKGROUND
Patients face increasing insurance restrictions on prescription drugs, including generic-only coverage. There are no generic inhaled corticosteroids (ICS), which are a mainstay of asthma therapy, and patients pay the full price for these drugs under generic-only policies. We examined changes in ICS use following the introduction of generic-only coverage in a Medicare Advantage population from 2003-2004.


METHODS
Subjects were age 65+, with asthma, prior ICS use, and no chronic obstructive pulmonary disorder (n = 1,802). In 2004, 74.0% switched from having a $30 brand-copayment plan to a generic-only coverage plan (restricted coverage); 26% had $15-25 brand copayments in 2003-2004 (unrestricted coverage). Using linear difference-in-difference models, we examined annual changes in ICS use (measured by days-of-supply dispensed). There was a lower-cost ICS available within the study setting and we also examined changes in drug choice (higher- vs. lower-cost ICS). In multivariable models we adjusted for socio-demographic, clinical, and asthma characteristics.


RESULTS
In 2003 subjects had an average of 188 days of ICS supply. Restricted compared with unrestricted coverage was associated with reductions in ICS use from 2003-2004 (-15.5 days-of-supply, 95% confidence interval (CI): -25.0 to -6.0). Among patients using higher-cost ICS drugs in 2003 (n = 662), more restricted versus unrestricted coverage subjects switched to the lower-cost ICS in 2004 (39.8% vs. 10.3%). Restricted coverage was not associated with decreased ICS use (2003-2004) among patients who switched to the lower-cost ICS (18.7 days-of-supply, CI: -27.5 to 65.0), but was among patients who did not switch (-38.6 days-of-supply, CI: -57.0 to -20.3). In addition, restricted coverage was associated with decreases in ICS use among patients with both higher- and lower-risk asthma (-15.0 days-of-supply, CI: -41.4 to 11.44; and -15.6 days-of-supply, CI: -25.8 to -5.3, respectively).


CONCLUSIONS
In this elderly population, patients reduced their already low ICS use in response to losing drug coverage. Switching to the lower-cost ICS mitigated reductions in use among patients who previously used higher-cost drugs. Additional work is needed to assess barriers to switching ICS drugs and the clinical effects of these drug use changes.
Fung
Vicki
V
Center for Health Policy Studies, Kaiser Permanente Division of Research, Oakland, California, USA. Vicki.Fung@kp.org
Tager
Ira B
IB
Brand
Richard
R
Newhouse
Joseph P
JP
Hsu
John
J
D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage* / Q000191:economics; D000368:Aged; D018927:Anti-Asthmatic Agents / Q000008:administration & dosage* / Q000191:economics; D001249:Asthma / Q000188:drug therapy / Q000191:economics*; D002986:Clinical Trials as Topic / Q000191:economics*; D017281:Cost of Illness; D003362:Cost-Benefit Analysis; D016568:Drugs, Generic / Q000191:economics / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D054524:Medicare Part D / Q000706:statistics & numerical data*; D014481:United States
D000305:Adrenal Cortex Hormones; D018927:Anti-Asthmatic Agents; D016568:Drugs, Generic