A pharmacy technician counts hydrocodone and acetaminophen tablets, also known as Vicodin, at the Oklahoma Hospital Discount Pharmacy in Edmond, Okla. (Sue Ogrocki/AP)

Current and former executives with the pharmaceutical distributors that are accused of flooding communities with powerful prescription painkillers have been summoned to testify before Congress about their role in the U.S. opioid epidemic.

The hearing, scheduled for May 8 before a House Energy and Commerce Committee oversight panel, has the potential to be a defining moment for the pharmaceutical industry, much like when tobacco executives were called to testify before Congress in 1994. The pharmaceutical executives are expected to face tough questions under oath about why their companies pumped so many highly addictive pain pills into West Virginia and other states, fueling what has become the deadliest drug crisis in U.S. history.

Since 2000, the epidemic has killed 200,000 people — more than three times the number of U.S. military deaths in the Vietnam War.

“It’s time to directly question the leadership of national and regional drug distributors whom we have probed for critical information,” Energy and Commerce Committee Chairman Greg Walden (R-Ore.) said in a statement.

Executives from distributors McKesson Corp., Cardinal Health, AmerisourceBergen, Miami-Luken and H.D. Smith wholesale drug company are scheduled to testify at the hearing next month.

The Energy and Commerce Committee has spent the past year investigating the sale of pills in West Virginia by wholesale drug distributors, which are required by law to monitor and report suspicious opioid orders to the Drug Enforcement Administration (DEA). If orders and sales are not correctly reported for oversight, countless doses of potent drugs can be diverted to a booming illegal market and ultimately to drug abusers — many of whom became hopelessly addicted to the powerful painkillers.

Committee members aggressively questioned Robert W. Patterson, the acting head of the DEA, last month, asking how so many pills flowed freely and why, they said, the agency wasn’t forthcoming with information about how it handled opioids.

The panel has sent letters to all of the distributors asking for information about steps they took to keep drugs off the black market and to report suspicious orders of pills.

“This investigation is taking a hard look at troubling issues behind the surge in opioid deaths in America,” Walden said. “We expect to get answers next month from these officials about the companies they represent.”

Cardinal Health, AmerisourceBergen and McKesson Corp. are the nation’s three biggest pharmaceutical distributors, responsible for shipping nearly 85 percent of all prescription drugs in the United States. McKesson is the fifth-largest company in the country, with revenue of more than $192 billion, according to the Fortune 500 list. Cardinal ranked 15th, with $121 billion in revenue.

McKesson said in a statement that it will “cooperate with the committee’s request,” and AmerisourceBergen said in a statement that it welcomes the opportunity to speak with the committee about the drug supply chain and the role of distributors: “We are committed to collaborating with all stakeholders on ways to combat opioid abuse, and look forward to a productive dialogue.”

John E. Parker, senior vice president of communications for the Healthcare Distribution Alliance, a national organization that represents primary pharmaceutical distributors, said in an email: “As an industry, we recognize the seriousness of the crisis and have advanced a comprehensive set of policy proposals to reduce overprescribing and address addiction as well as efforts to improve prevention and education. Further, distributors have invested substantially in the use of state-of-the-art tools to detect and prevent potential diversion. We will continue to work with policymakers to advance meaningful solutions to effectively address this epidemic.

The panel hearing could provide more of a road map for how the powerful narcotics made their way to individual communities, some of which received massive amounts of drugs per capita. Committee members hope the hearing will shed light on specific data the companies reported to the DEA about how many pills they sent and where the pills went. That information is kept on a confidential DEA database known as the Automation of Reports and Consolidated Orders System. The database tracks the flow of prescription painkillers from manufacturers to distributors to pharmacies.

The committee and news reports have disclosed some of the data, and it is staggering: Millions of pills were shipped to small communities in West Virginia, which has the nation’s highest rate of drug overdose deaths.

In February, the panel revealed in letters sent to the firms that McKesson and Cardinal Health shipped 12.3 million doses of powerful prescription opioids to the Family Discount Pharmacy in Mount Gay-Shamrock, W.Va., from 2006 to 2014. The town in southern West Virginia had 1,779 residents, according to the 2010 Census.

An analysis by the committee found that Cardinal Health sent the pharmacy more than 6.5 million hydrocodone and oxycodone pills between 2008 and 2012. McKesson sent 5.8 million pills from 2006 to 2014. Other distributors also sold painkillers to the pharmacy, bringing the total to nearly 16.6 million by 2016.

In letters sent to the smaller distributors in January, the committee cited data showing that wholesalers shipped nearly 21 million doses of painkillers to two pharmacies just blocks apart from each other in Williamson, W.Va., a town of 3,191 on the Kentucky border about 30 miles from Mount Gay-Shamrock. The letter said that Miami-Luken sent about half of the pills.

The town received “approximately 1,565 hydrocodone and oxydocone pills for every man, woman and child” from Miami-Luken in 2007 and 2008, according to a letter sent by the panel.

In total, Miami-Luken shipped 20 million doses of hydrocodone and oxycodone to West Virginia pharmacies from 2007 to 2012. The company was being investigated by the DEA’s Detroit office, but a program officer said his entreaties to close down the company were ignored by superiors in Washington.

“We are continuing to cooperate with the committee,” said Richard Blake, an attorney representing Miami-Luken.

The DEA data also is being sought as part of a mammoth court case in Cleveland. Hundreds of lawsuits filed by municipalities against opioid manufacturers, distributors and pharmacies have been consolidated in a federal court there.

The judge in the case, Dan Aaron Polster of the Northern District of Ohio, ruled Wednesday that the DEA must turn over transactional business data and suspicious order reports the companies filed for their activity in Alabama, Florida, Illinois, Michigan, Ohio and West Virginia between Jan. 1, 2006, and Dec. 31, 2014. The DEA must provide the data to Polster by April 20. Alhough lawyers for the defendants and plaintiffs in the case will have access to the data, it will be sealed from public view under a court-imposed protective order.

Lawmakers and lawyers think the data could show a correlation between shipments of opioids and deaths in those communities. The DEA initially fought the release of the data, but Polster rejected the agency’s arguments.

“The vast oversupply of opioid drugs in the United States has caused a plague on its citizens and local governments,” Polster wrote in his ruling. The request for the data is “a reasonable step toward defeating the disease.”

Paul Farrell Jr., a West Virginia lawyer who represents plaintiffs in the case, praised Polster for ordering the release. He said the order could be a “tipping point” in the case, revealing patterns of drug shipments and deaths and how the flood of prescription pain pills fueled a national epidemic.

The information “has the potential to serve as a Rosetta Stone to decipher and understand how prescription opiate abuse evolved into a national epidemic,” Farrell said.