Impact of medicare part D plan features on use of generic drugs.
BACKGROUND
Little is known about how Medicare Part D plan features influence choice of generic versus brand drugs.


OBJECTIVE
To examine the association between Part D plan features and generic medication use.


METHODS
Data from a 2009 random sample of 1.6 million fee-for-service, Part D enrollees aged 65 years and above, who were not dually eligible or receiving low-income subsidies, were used to examine the association between plan features (generic cost-sharing, difference in brand and generic copay, prior authorization, step therapy) and choice of generic antidepressants, antidiabetics, and statins. Logistic regression models accounting for plan-level clustering were adjusted for sociodemographic and health status.


RESULTS
Generic cost-sharing ranged from $0 to $9 for antidepressants and statins, and from $0 to $8 for antidiabetics (across 5th-95th percentiles). Brand-generic cost-sharing differences were smallest for statins (5th-95th percentiles: $16-$37) and largest for antidepressants ($16-$64) across plans. Beneficiaries with higher generic cost-sharing had lower generic use [adjusted odds ratio (OR)=0.97, 95% confidence interval (CI), 0.95-0.98 for antidepressants; OR=0.97, 95% CI, 0.96-0.98 for antidiabetics; OR=0.94, 95% CI, 0.92-0.95 for statins]. Larger brand-generic cost-sharing differences and prior authorization were significantly associated with greater generic use in all categories. Plans could increase generic use by 5-12 percentage points by reducing generic cost-sharing from the 75th ($7) to 25th percentiles ($4-$5), increasing brand-generic cost-sharing differences from the 25th ($25-$26) to 75th ($32-$33) percentiles, and using prior authorization and step therapy.


CONCLUSIONS
Cost-sharing features and utilization management tools were significantly associated with generic use in 3 commonly used medication categories.
*Department of Health Policy and Management, Graduate School of Public Health, University of Pittsburgh †VA Pittsburgh Healthcare System ‡Division of General Medicine and Center for Pharmaceutical Policy and Prescribing, University of Pittsburgh §RAND Health, Pittsburgh PA.
Yan
Y
Tang
Walid F
WF
Gellad
Aiju
A
Men
Julie M
JM
Donohue
D000368:Aged; D000928:Antidepressive Agents / Q000191:economics / Q000627:therapeutic use; D017046:Cost Savings; D017047:Cost Sharing / Q000191:economics; D004363:Drug Utilization / Q000191:economics / Q000706:statistics & numerical data; D016568:Drugs, Generic / Q000191:economics* / Q000627:therapeutic use*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000191:economics / Q000627:therapeutic use; D007004:Hypoglycemic Agents / Q000191:economics / Q000627:therapeutic use; D054524:Medicare Part D / Q000191:economics*; D054539:Medication Therapy Management / Q000191:economics; D014481:United States
D000928:Antidepressive Agents; D016568:Drugs, Generic; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007004:Hypoglycemic Agents