The implications of choice: prescribing generic or preferred pharmaceuticals improves medication adherence for chronic conditions.
BACKGROUND
A large proportion of Americans are enrolled in 3-tier pharmacy benefit plans. We studied whether patients enrolled in such plans who receive generic or preferred brand-name agents when initiating chronic therapy were more adherent to treatment than those who received nonpreferred brand-name medications.


METHODS
We analyzed pharmacy claims filled between October 1, 2001, and October 1, 2003, from a large health plan for 6 classes of chronic medications: 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, calcium channel blockers, oral contraceptives, orally inhaled corticosteroids, angiotensin receptor blockers, and angiotensin-converting enzyme inhibitors. We measured adherence as the proportion of days covered (PDC) in each drug class during the first year of therapy. We evaluated how the formulary status of the initial prescription (generic, preferred, or nonpreferred) influenced PDC and adequate adherence, defined as PDC greater than 80%, over the subsequent year.


RESULTS
A total of 7532 new prescriptions were filled in 1 of the classes evaluated: 1747 (23.2%) for nonpreferred medications, 4376 (58.1%) for preferred drugs, and 1409 (18.7%) for generic drugs. After controlling for patient sociodemographic characteristics and drug class, PDC was 12.6% greater for patients initiated on generic medications vs nonpreferred medications (58.8% vs 52.2%; P<.001). The PDC was 8.8% greater for patients initiated on preferred vs nonpreferred medications (56.8% vs 52.2%; P<.001). Patients initiated on generic and preferred medications had 62% and 30% greater odds, respectively, of achieving adequate adherence compared with those who received nonpreferred medications.


CONCLUSIONS
In 3-tier pharmacy benefit plans, prescribing generic or preferred medications within a therapeutic class is associated with improvements in adherence to therapy.
Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital and Harvard Medical School, Boston, Mass, USA. wshrank@partners.org
William H
WH
Shrank
Tuyen
T
Hoang
Susan L
SL
Ettner
Peter A
PA
Glassman
Kavita
K
Nair
Dee
D
DeLapp
June
J
Dirstine
Jerry
J
Avorn
Steven M
SM
Asch
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D000367:Age Factors; D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D002121:Calcium Channel Blockers / Q000627:therapeutic use; D002908:Chronic Disease / Q000188:drug therapy*; D003276:Contraceptives, Oral / Q000627:therapeutic use; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D016568:Drugs, Generic; D005260:Female; D005569:Formularies as Topic; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D007356:Insurance, Pharmaceutical Services; D008297:Male; D010349:Patient Compliance; D012737:Sex Factors; D014481:United States
D000305:Adrenal Cortex Hormones; D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D002121:Calcium Channel Blockers; D003276:Contraceptives, Oral; D016568:Drugs, Generic; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors