Methamphetamine and cocaine overdose deaths are on the rise across the United States, according to new data from the Centers for Disease Control and Prevention (CDC).

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The CDC said 63,632 drug overdose deaths were reported in 2016.

While 66 percent of those deaths involved an opioid, deadly overdoses from cocaine and other stimulants saw the largest increase, with a 52.4 percent rise in deaths between 2015 and 2017, according to the CDC.

Opioid overdoses rose about 27 percent in the same time period, the government data shows.

The reason for this increase in stimulant overdoses is unknown, but opioid users report difficulty staying awake. Experts said they often turn to stimulants to function.

"If you talk to heroin users, they totally use meth to keep them up," Dr. Karen Randall, an emergency room doctor in Pueblo, Colorado, told WebMD. "They use heroin, but then they have to take the kids to school, they have to get up and do stuff, (so) they use methamphetamines."

A new report from NPR's Morning Edition finds that the combination of meth and heroin might be due in part to the drug Vivitrol.

Vivitrol blocks receptors in the brain related to opioid addiction, but it does not block the receptors triggered by methamphetamine, WLS reports.

Paramedics in rural Ohio told NPR that local people in recovery were using the drug Vivitrol to wean off heroin, but switched to stimulants to get high.

Listen to the report from NPR: