A bitter pill: formulary variability and the challenge to prescribing physicians.
BACKGROUND
Multitiered, incentive-based formularies have been increasingly used as a mechanism to control prescription drug expenditures. Prescribing physicians who manage patients from multiple insurers must be familiar with the variability in their patients' formulary incentives to help patients choose therapy wisely. However, the degree of formulary variability among and within health plans over time is unclear.


METHODS
In 6 major health plans in California, we evaluated formulary incentive variability in 4 of the 5 drug classes with the highest expenditures in California: proton pump inhibitors, hydroxymethylglutaryl coenzyme A reductase inhibitors ("statins"), calcium channel blockers, and angiotensin-converting enzyme inhibitors. We categorized 20 branded members of these classes into either "preferred" or nonpreferred/uncovered categories. We calculated the consistency that brands were preferred across health plans and the frequency of changes in formulary status for each drug within plans between 2000 and 2002.


RESULTS
None of the branded drugs evaluated were preferred on all formularies in 2002, and 10% were not available on any of the formularies. Formulary status varied greatly across plans, and more than 60% of drugs were preferred on 2 to 4 of the 6 formularies studied. Formulary status within health plans varied between 2000 and 2002 in more than half of the plans in the drug classes evaluated.


CONCLUSIONS
In the drug classes evaluated, over a 2-year period, considerable variability was seen among and within formularies over time. This variability poses a challenge to physicians who wish to reduce patients' expenditures by prescribing the least expensive among similarly effective drugs within a drug class. This variability is especially relevant because recent legislation increases the likelihood that more Medicare beneficiaries will receive their medications from private health plans.
Shrank
William H
WH
Division of General Internal Medicine, VA Greater Los Angeles Health Care System, Los Angeles, CA 90073, USA. william.shrank@med.va.gov
Ettner
Susan L
SL
Glassman
Peter
P
Asch
Steven M
SM
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000191:economics; D002121:Calcium Channel Blockers / Q000191:economics; D002140:California; D017047:Cost Sharing; D016527:Drug Costs; D017723:Drug Utilization Review; D005569:Formularies as Topic; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000191:economics; D008329:Managed Care Programs / Q000191:economics* / Q000639:trends; D010593:Pharmaceutical Services / Q000191:economics / Q000706:statistics & numerical data*; D011306:Prescription Fees; D054328:Proton Pump Inhibitors; D017494:Proton Pumps / Q000191:economics; D012189:Retrospective Studies
D000806:Angiotensin-Converting Enzyme Inhibitors; D002121:Calcium Channel Blockers; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D054328:Proton Pump Inhibitors; D017494:Proton Pumps