The State Compensation Insurance Fund, one of the largest providers of workers’ compensation insurance in California, has cut its spending on prescription opioids by 74 percent amid a broader push by insurers and doctors to reduce the long-term use of addictive prescription painkillers.

State Fund, as it is often called, slashed spending on opioids from $21.7 million in 2014 to $5.6 million in 2017, the agency announced Thursday. It also reduced the number of opioid prescriptions it covered by 60 percent during the same period, from 140,300 prescriptions to 56,200.

The agency’s spending on opioids, as a proportion of its overall spending on prescription drugs, shrank from 25 percent to 17 percent.

The reductions are part of a broader effort in the health care industry to decrease the use of prescription opioids, or reduce the amount of time that patients take them. In 2016, a record 42,000 Americans died from opioid overdoses, many of them from prescriptions.

State Fund insures about 110,000 employers in California for workplace injuries and collects roughly 10 percent of all workers’ comp insurance premiums in the state — more than any other workers’ comp insurer except Berkshire Hathaway.

State Fund was created by the California Legislature in 1914 and is a quasi-public agency. Most of its employees are state employees, but it operates more like a private insurer, collecting revenue from insurance premiums paid by employers.

In 2014, State Fund began a concerted effort to reduce opioid prescriptions. It focused on preventing newly injured workers from getting on prescription opioids in the first place, and on reducing opioid use among injured workers who had been taking the drugs, in some cases, for many years.

One change imposed new restrictions on how long patients could take opioids — from 90 days to 30 days — before the case gets reviewed by an outside group of medical experts. Soon, the 30-day period will be shortened even more, to just four days.

Patients are encouraged to seek other treatments like acupuncture and physical therapy and, for those coping with addiction, cognitive behavioral therapy and treatment programs for opioid dependence.

“Through this effort, we have helped to improve — and potentially save — the lives of many injured workers, while also reducing expenses in the workers’ compensation system for California businesses,” State Fund President and CEO Vern Steiner said in a statement.

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat_Ho