In a one-page investigative summary, Inspector General Michael Horowitz said the unnamed official "misused" his or her official position by giving preferential treatment to the pharmaceutical company and pressured subordinates to approve the quota increase.
The increase was requested by a second unnamed former DEA official who worked for the company, the report said.
The former DEA official at the heart of the watchdog's internal probe also apparently planned to work for the pharmaceutical company upon retirement and "lacked candor" with the DEA's Office of Chief Counsel in disclosing those plans, Horowitz's report said.
"The senior DEA official misused the senior official's position at DEA by giving preferential treatment to a request by the pharmaceutical company that employed the former DEA official," the report says. "The senior DEA official pressured and directed subordinates to approve the request."
A spokesperson for the DEA did not have any immediate comment on the findings.
The inspector general's report does not identify the company at issue, or whether the former senior official ultimately went to work there.
Because the Justice Department's inspector general only has the legal authority to compel testimony from current employees, the official was able to retire and declined to voluntarily appear for questioning.
The department also declined to prosecute the official who gave preferential treatment to the drugmaker.
The DEA has come under scrutiny in recent years for its role in helping to exacerbate the ongoing U.S. opioid crisis.
The agency uses a quota system that is designed to ensure that drug manufacturers are able to produce enough drugs for medical, scientific, research and industrial needs.
The quotas apply to drugs that are deemed to be addictive, and fall into schedules I and II.
Critics have accused the DEA of failing to proactively cut the supply of painkillers manufactured in the United States by simply limiting the annual quota.
(Reporting by Sarah N. Lynch, Editing by Rosalba O'Brien)
By Sarah N. Lynch