Dealers are turning to fentanyl because it's made in a lab, it's cheap to make and profit margins are high. The local DEA suspects the synthetic drugs are coming from China.
Users like fentanyl - considered 50 to 100 more potent than heroin - because it produces a stronger high, officials say.
But because the synthetics are more lethal than heroin, overdose deaths are increasing.
In Butler County, 72 percent of the 153 heroin deaths last year involved a form of fentanyl. The scariest part: many users don't know what they're buying.
"They'd only find out once they end up in our facility that what they got was not heroin,” said Martin Schneider of the Butler County Coroner’s Office.
The spread of synthetic opiates is also forcing emergency crews and law enforcement to change life-saving tactics.
Officers carry more narcan and in stronger doses, Synan said.
"It's changed how we've done law enforcement. When we first started putting narcan out, it was 2-milligram kits. And we started noticing that officers on the streets and paramedics were using two or three kits at one time and the person still wasn't being revived.
“Now we give out 4-milligram kits of narcan and usually you'll use two or three of those just to revive somebody," he said.
From his standpoint, Synan says the war on drugs has gotten a lot harder.
"It was already complicated. It was already difficult. Now it's a 1,000 times more difficult with the introduction of synthetics," he said.
"It's cheaper for the drug traffickers to use, it's easier for them to get. They don't have to go through the processing of plants ... whether it's in Butler County, Warren County or Northern Kentucky -- it impacts us all."