On July 18, 2017, the DWC released a draft of its proposed regulations governing the California Workers’ Compensation Prescription Drug Formulary, including modifications made following a public hearing on May 1, 2017. These regulations included a number of modifications and distinct changes from the draft regulations that DWC released on August 26, 2016, including revisions to the Formulary’s Exempt and Non-Exempt Drug Lists, an expanded list of Special-Fill Drugs, and a new category of 14 Perioperative drugs that may be dispensed under specified conditions. This report uses data from 650,000 California workers’ comp prescriptions with 2016 fill dates to assess the impact of the proposed Formulary and Drug Lists on California workers’ compensation prescribing patterns and uses 2016 Utilization Review and Independent Medical Review data to measure the Formulary’s potential impact on the volume of medical disputes involving pharmaceutical requests.