Some states are seeing a significant decrease in the amount of opioids received by injured workers, according to a new study. Reductions between 20 percent and 31 percent were seen in Maryland, Massachusetts, Michigan, Oklahoma, North Carolina, and Texas.

The study, by the Workers Compensation Research Institute, looked at 337,000 workers’ compensation claims in 25 states, and the 1.9 million prescriptions linked to those claims. The study compared the amount of opioids prescribed per claim over two 24-month periods. One period ended in March 2012, and the other in March 2014.

The reductions in opioid claims coincided with reforms directed at opioid use, HealthDay reports.

Workers who were off work for more than seven days were most likely to be prescribed opioids. Between 65 percent and 80 percent of these injured workers who were given pain medications received opioids in most states. Injured workers in Louisiana, New York and Pennsylvania were prescribed the highest average amounts of opioids.

Between 1 percent and 9 percent of injured workers were simultaneously prescribed opioids and benzodiazepines, while between 30 percent and 45 percent simultaneously received prescriptions for opioids and muscle relaxants.

“This information should be useful for state officials who wonder if the use of opioids is unusual in their state, payors and managed care companies looking to set priorities for targeting opioid management programs, injured workers and worker advocates looking to understand the extent of the problem in their state, and providers who wonder what the prescribing norms in their state may be and if the state norms are unusual,” Dr. Vennela Thumula, an author of the study, said in a news release.