By Carla K. Johnson, AP Medical Writer

CHICAGO (AP) — Nearly 12 million Medicare beneficiaries received at least one prescription for an opioid painkiller last year at a cost of $4.1 billion, according to a federal report (pdf) that shows how common the addictive drugs are in many older Americans' medicine cabinets.

With an overdose epidemic worsening, nearly one-third of Medicare beneficiaries received at least one prescription for commonly abused opioids such as OxyContin and fentanyl in 2015. Those who did received an average of five such prescriptions or refills, according to the report from the Office of Inspector General for the U.S. Department of Health and Human Services.

"We are concerned about the high spending and the number of people receiving opioids," said Miriam Anderson, who led the study, which was released Wednesday. "This raises concerns about abuse. This is a serious problem facing our country."

Among all ages, there were nearly 19,000 fatal overdoses on prescription opioids in 2014, which was the most on record and the last year for which that data set was available.

The magnitude of opioid use among seniors is "astounding," said Frederic Blow, who directs addiction research at the University of Michigan's medical school and was not involved in the study.

"It's not just a young person's problem," Blow said. Overdose risk for older Americans is heightened by medication interactions and alcohol. Addiction is also a risk and doctors should help patients consider alternatives for chronic pain, such as meditation, yoga, walking and weight loss, which allow patients to minimize opioid use.

The leading opioids taken by Medicare patients were OxyContin, Percocet, Vicodin, fentanyl or their generic equivalents, Anderson said. "In fact, there were about 40 million prescriptions for these drugs last year," she said. "That's enough to give one to every Medicare beneficiary in the country."

In February testimony on opioid use among seniors to Congress, Centers for Medicare and Medicaid Services Deputy Administrator Sean Cavanaugh said the agency "is aware of potential fraud at the prescriber and pharmacy levels through 'pill mill' schemes."

Medicare is reviewing the report closely, spokesman Aaron Albright said. The agency has had a monitoring system since 2013 that provides quarterly reports to Part D plan sponsors on high-risk beneficiaries who may be overusing commonly abused drugs. The system flagged 15,651 beneficiaries last year as potential problem drug users. In 2017, the federal government will bar payment for prescriptions written by doctors who are not enrolled in Medicare.

"Medicare Part D spending on opioids, in general, is decreasing as a percent of total Part D spending, from 3.2 percent in 2014 to 3.0 percent in 2015," Albright said. The agency "takes seriously our responsibility to ensure that beneficiaries have access to the drugs they need with appropriate safeguards to prevent abuse."

To Learn More:

High Part D Spending on Opioids and Substantial Growth in Compounded Drugs Raise Concerns (Office of Inspector, Department of Health and Human Services) (pdf)

Heart-Related Deaths, Not Only Overdoses, Tied to Opioid Painkiller Use (by Lindsey Tanner, Associated Press)

CDC Urges Doctors to Render Prescription Painkillers a Last Resort (by Matthew Perrone, Associated Press)

U.S.: 5% of World Population; 80% of Opioid Consumption (by Steve Straehley, AllGov)

U.S. Doctors Prescribe Opiate Painkillers at Twice the Rate of any other Country…and 500,000 Veterans are Dependent (by Steve Straehley, AllGov)