One in four Sonoma County residents had an opioid prescription in 2014, a figure that troubles health care officials battling a national epidemic of prescription drug abuse.

Hydrocodone, by far the most widely prescribed opioid in Sonoma County, comprised 57 percent of the 459,000 opioid prescriptions filled at local pharmacies, according to a new report by the county Department of Health Services. Oxycodone made up 18 percent of local prescriptions.

“Twenty five percent of our residents are taking an opioid at some point in time during the year; that’s a very high number,” said county health officer Karen Milman.

Some of the data used in the county report comes from the Controlled Substance Utilization Review and Evaluation System, the state’s prescription drug monitoring program. Milman said 2014 represented the first full year of data available to the county.

Milman said the information offers a “baseline” of data that allows local health officials and health care professionals to examine ways of preventing prescription drug abuse.

“This is not unique to Sonoma County. This is happening nationwide,” Milman said.

Part of the data from the report uses three-year “rolling averages” that span the period between 2009 and 2014. County health officials found that nonfatal emergency department visits for opioid use increased 73 percent during that time. The three-year average grew to 17.3 visits per 100,000 people between 2012 and 2014, up from 10 visits for every 100,000 residents between 2009 and 2011.

About 126,000 people in Sonoma County were prescribed opioids in 2014. Of those, 58 percent were women. Just over half of the patients, or 53 percent, had only one opioid prescription, while 25 percent had four or more opioid prescriptions.

The median age for these opioid users was 53.

The report found 71 percent of received their prescriptions from only one prescriber. There were 524 “doctor shoppers,” patients who obtain opioid prescriptions from four or more prescribers and four or more pharmacies.

But Milman said there are signs that the local opioid epidemic is improving, thanks to an initiative by Partnership HealthPlan of California, the nonprofit managed-care giant that administers the county’s Medi-Cal program.

That initiative was created to fight the overuse of opioid pain medications such as OxyContin and Vicodin, ensuring that they are used only when medically necessary. It has led to a 23 percent reduction in the prescribing of opioid-based pain medications for patients on Medi-Cal, health officials said.

The reduction occurred between the fourth quarter of 2013 and the fourth quarter of 2014. Overall, Partnership HealthPlan, which serves 14 Northern California counties, has seen a 40 percent drop in the use of long-acting opioid pain medication among its members.

Milman said the data used by Partnership HealthPlan is newer than that cited in the county report published Friday.

“Their whole initiative was launched toward the end of this data,” Milman said. “The decreases that they have seen, we don’t yet have the data for. ... I’m confident our numbers are going down because of their initiative.”

You can reach Staff Writer Martin Espinoza at 521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @renofish.