California Workers’ Compensation Institute (CWCI)

Study Examines Prescription Drug UR/IMR Outcomes Under the New California Workers’ Comp Formulary

The results of a study conducted by the California Workers’ Compensation Institute (CWCI) of preliminary results of Utilization Review (UR) and Independent Medical Review (IMR) outcomes have been released. The study measured, among other key issues, changes in UR and IMR decisions after the January 1, 2018, adoption of legislation mandating an evidence-based formulary for medications prescribed to California injured workers.

Key findings of the study included:

  • The proportion of UR decisions involving prescription drug requests fell from 44.5 percent in the pre-formulary period to 40.7 percent in the first five months of 2018, a relative decline of 8.5 percent.
  • The percentage of UR decisions in which a prescription drug request was denied was unchanged at 14.6 percent.
  • UR decisions involving opioid requests showed little change, edging down from 30.6 percent in the pre-formulary period to 30.0 percent after the formulary took effect.
  • The UR approval rate for opioids fell from 72.3 percent to 68.8 percent

CWCI says that more time is needed to identify changes in prescribing patterns and other aspects of the formulary regulations that could impact UR and IMR disputes, so it will continue to monitor the results and take an expanded look at first-year formulary outcomes in a study scheduled for 2019.

Several states have implemented formularies over the past few years, and several more are currently considering or developing formularies. California’s drug formulary is unique in that the California Division of Workers’ Compensation chose to develop a custom drug list based on medical treatment guidelines produced by American College of Occupational and Environmental Medicine.

The full report, “Initial UR and IMR Prescription Drug Outcomes Under the California Workers’ Comp Formulary,” is available at