The drugs driving overdose deaths vary depending on where you live in the U.S., a government report published Friday found.

When researchers from the Centers for Disease Control and Prevention's National Center for Health Statistics analyzed death certificates from 2017 and searched for names of specific drugs involved in overdoses, they found distinct differences on each side of the Mississippi River.

Drug overdoses in the eastern part of the U.S. were much more likely to involve the synthetic opioid fentanyl, while methamphetamine dominated in the West.

Nationwide, fentanyl was the most common drug implicated in 2017, reported in 38.9 percent of the more than 70,000 drug overdose deaths that occurred that year.

Heroin and cocaine were used in 22.8 percent and 21.3 percent of drug overdose deaths, respectively. Methamphetamine was the fourth drug most frequently involved, found in 13.3 percent of overdose deaths. Many times, drug overdose deaths involved more than one substance.

"Knowing what's going on in different parts of the country helps inform prevention efforts," said Dr. Holly Hedegaard, the lead author of the report and a medical epidemiologist with the National Center for Health Statistics.

Hedegaard gave the example of naloxone, which is used to reverse opioid overdoses. Naloxone, sold as Narcan, is particularly effective in areas of the country with higher rates of opioid addiction, such as the Northeast.

The medication is so important in reducing opioid-related deaths that emergency departments within the University of Pittsburgh Medical Center (UPMC) have given away more than 1,000 naloxone kits to people considered at high risk for an overdose.

"Our system just pays for it. We hand them a Narcan nasal spray kit to walk out the door with," said Dr. Mike Lynch, medical director for the Pittsburgh Poison Center at UPMC. He was not involved in the new research.

But bystanders or first responders don't have any comparable tools to treat people who have taken too much methamphetamine. What's more, these individuals present a particular risk to bystanders and first responders, Lynch said.

"That person is going to be agitated, delirious, potentially hallucinating or violent," he said. For meth overdoses, doctors must use a combination of sedatives and antipsychotics to calm the individual.

But even then, Lynch said, "it isn't truly an antidote, or a reversal."

While the 2017 data implicated fentanyl in the majority of overdoses in the East, and methamphetamine in the West, newer data from the CDC suggests trends may be shifting.

That set of data includes drug overdose deaths from 2018 to March of this year. During that time, fatal overdoses dropped in the Midwest and eastern portion of the U.S., where naloxone has been widely implemented.

But the more recent data also shows overdose deaths in the West are rising overall — a possible sign deadly fentanyl is migrating, according to experts.

Conversely, Lynch said that over the past year or two, the Pittsburgh Poison Center has witnessed a growing number of patients addicted to methamphetamine.

"As both the West adjusts to fentanyl and the Midwest and Northeast respond to methamphetamine increases, we can learn from each other," Lynch said.

The new study from the NCHS also identified other drugs commonly seen in overdose deaths nationwide.

Those include sedatives such as aplrazolam (sold as Xanax), clonazepam (sold as Klonopin) and diazepam (sold as Valium), as well as the antihistamine diphenhydramine (sold as Benadryl), and a number of other powerful narcotics and opioids.

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