The findings of a new Stanford-led study suggest that illicit drugs are beginning to replace prescription opioids as the source of the national drug epidemic.

Hospital discharges related to prescription opioids have declined slightly in recent years, but heroin-related discharges have surged, according to a new study led by researchers at the Stanford University School of Medicine.

“This suggests that the expanded availability of lethal illicit drugs are being used to replace prescription opioids in some cases,” said Tina Hernandez-Boussard, PhD, associate professor of medicine, of biomedical data sciences and of surgery at Stanford. The decrease in hospital discharges due to prescribed opioids could be an indication that initiatives to curtail their over-prescription are beginning to work, she said.

The study was published online October 2 in the journal Health Affairs.

Hernandez-Boussard is the senior author. Former Stanford postdoctoral scholar Dario Tedesco, PhD, is the lead author.

The study showed that discharge rates for prescription opioid poisonings declined annually by about 5 percent from 2010 to 2014 while discharge rates for heroin poisoning increased at an annual rate of 31.4 percent from 2008 to 2014.

The findings add evidence to recent public health concerns that individuals misusing or addicted to prescription opioids are switching to heroin and synthetic opioids, such as fentanyl, because they are cheaper and easier to get, Hernandez-Boussard said. Preliminary statistics from the Centers for Disease Control and Prevention also support this trend, showing that both heroin and synthetic drugs overtook deaths due to prescription opioids in 2016.

Figures remain frighteningly high for all types of opioid use, contributing to what many are calling the worst drug epidemic in United States history, she said. Opioid deaths in the United States now surpass those due to automobile accidents, the study said.

“In the last decade, opioid-related death rates have nearly tripled, opioid-related hospital visits have dramatically increased and misuse of prescription opioids is reaching alarming levels,” the study said.

Researchers analyzed national trends in hospital inpatient and emergency department discharges for opioid abuse, dependence and poisoning from 1997 to 2014, using data from the Healthcare Cost and Utilization Project, a hospital care database.

From 2010 to 2014 — the last year that data were available — researchers found a significant decrease in hospital admissions for prescription opioid overdoses, which coincided with national public health efforts to reduce the availability of these drugs, Hernandez-Boussard said.

“While there has been a significant increase in opioid-related admissions over the past two decades, in 2010 admissions for prescription opioid misuse began to decline,” she said.

In 2010, following President Barack Obama’s release of the first National Drug Control Strategy, which emphasized the need for action to battle opioid misuse, addiction and overdose deaths, there were a lot of federal, national and societal initiatives targeting reductions in opioid prescriptions, she said.

“That’s the good news. The bad news is that although prescription opioid use decreased, heroin and methadone greatly increased,” Hernandez-Boussard said.

She added, “I’m cautiously optimistic that prescribing clinicians are positively reacting to the opioid crisis and therefore prescription opioids are contributing less to the overall drug epidemic.”

Anna Lembke, MD, associate professor of psychiatry at Stanford and author of Drug Dealer, MD: How Doctors Were Duped, Patients Got Hooked, and Why It’s So Hard to Stop, said she has no doubt many of those addicted to prescription opioids have switched to using heroin or synthetic opioids like fentanyl.

“My patients have told me that