Monitoring Trends after Adoption of California’s Drug Formulary

By Vennela Thumula, Te-Chun Liu

March 30, 2023 Related Topics: Drug Formularies, Physician Dispensing, Rx Drugs and Opioids

This report is a part of a series of studies that examine the impact of drug formularies in five states (Arkansas, California, Indiana, Kentucky, and New York) that implemented formularies in 2018 and 2019. As of January 1, 2023, 17 states have adopted drug formularies, with several other states considering implementation. Findings of this study should therefore be of interest to stakeholders in California as well as those in other states considering implementation of drug formularies in their jurisdictions. 

In this study, we examine the impact of California’s workers’ compensation drug formulary on prescription drug utilization and costs using detailed transaction data for prescriptions filled between January 1, 2016, and March 31, 2021, by workers within 12 months of injury. California’s Medical Treatment Utilization Schedule (MTUS) drug formulary went into effect on January 1, 2018. 

Monitoring Trends after Adoption of California’s Drug Formulary. Vennela Thumula and Te-Chun Liu. March 2023. WC-23-22.

Copyright: WCRI

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Research Questions:

  • Did the formulary reduce overall prescription utilization?
  • What was the impact on drugs with different status under the California MTUS formulary—non-exempt drugs, exempt drugs, and unlisted drugs?
  • Was there a differential effect on physician- and pharmacy-dispensed prescriptions?
  • What was the impact on various drug groups—opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), dermatological agents, musculoskeletal therapy agents, anticonvulsants, compounds, and others? 
  • How did generic utilization change after the drug formulary? 
  • Did the formulary reduce prescription payments per claim?

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