When the U.S. Department of Justice announced on Aug. 6 that MWI Veterinary Supply Inc. had agreed to pay $100,000 to resolve allegations that it failed to identify suspicious opioid orders from a West Virginia veterinarian, the settlement appeared to close the book on a federal enforcement action.
In reality, it closed the final chapter of an investigation that began nearly three years earlier with a DEA inspection of a rural veterinary practice and ultimately expanded beyond one veterinarian to examine the responsibilities of one of the nation’s largest veterinary pharmaceutical distributors.
MWI Animal Health, owned by healthcare distributor Cencora (formerly AmerisourceBergen), agreed to resolve allegations that it failed to recognize unusually large oxycodone orders as suspicious and notify the Drug Enforcement Administration, as required under the Controlled Substances Act. Federal investigators alleged the company continued filling opioid orders after its own internal monitoring system identified one of the purchases for additional review.
To understand how the investigation reached MWI, however, requires rewinding to October 2023.
A Routine Inspection Becomes a Federal Investigation
On Oct. 11, 2023, DEA investigators executed an Administrative Inspection Warrant at the home and veterinary practice of Dr. Clara Ann Mason, a mixed-animal veterinarian in Putnam County, W.Va.
According to later court filings, investigators identified at least 51 alleged violations of the Controlled Substances Act during the inspection.
Rather than immediately filing suit, the government spent months attempting to resolve the matter. Mason and her attorney met with investigators in March 2024, and prosecutors considered a reduced settlement based on her claimed inability to pay. Court records indicate those negotiations ultimately stalled after requested financial information was never provided.
When negotiations failed, the United States filed a civil complaint in March 2025 alleging Mason had failed to maintain records required of DEA registrants who handle controlled substances.
The case centered on recordkeeping requirements rather than allegations of criminal diversion.
A federal judge ultimately entered a default judgment totaling $956,709, including penalties for:
- 44 violations involving missing DEA Form 222 order forms;
- six violations for failing to maintain dispensing records; and
- one violation for failing to maintain the required biennial inventory of controlled substances.
Thousands of Doses Raise Red Flags
Federal investigators alleged that even after reviewing Mason’s dispensing records, approximately 9,796 dosage units of controlled substances remained unaccounted for, including hydrocodone, oxycodone, tramadol, ketamine and Vetorphic.
The government also stated that although investigators identified at least 51 violations during the inspection, prosecutors initially pursued only a limited number of counts because Mason had represented that she possessed few financial assets. Prosecutors later told the court they had discovered substantial real estate holdings and indicated they would seek permission to amend the complaint with additional violations if the judgment were set aside.
Throughout the litigation, Mason attempted to overturn the default judgment, arguing that severe health problems had prevented her from adequately responding to the lawsuit.
In later court filings, she acknowledged a negligent failure to maintain required purchasing, dispensing and inventory records for controlled substances. She also stated that years of debilitating medical conditions led her to self-medicate for chronic pain, which ultimately developed into addiction. Mason voluntarily surrendered both her veterinary license and her DEA registration in November 2025.
Her attorney argued that while Mason accepted responsibility for negligent recordkeeping, she disputed the government’s characterization of other allegations and believed those issues should have been decided by a jury.
The judge ultimately denied Mason’s requests to reopen the case, concluding that although her medical condition was serious, it did not constitute a legal defense to the underlying recordkeeping violations. The court also found Mason had failed to present evidence challenging the majority of the violations, particularly the 44 missing DEA Form 222 order forms that accounted for most of the civil penalties.
The Investigation Reaches MWI
While investigators were examining Mason’s controlled-substance records, they also scrutinized how those medications had been supplied.
According to the DOJ settlement with MWI, federal investigators found that between March 2018 and July 2023 the distributor filled orders for 14,200 dosage units of hydrocodone/acetaminophen, 800 dosage units of 10 mg oxycodone and 600 dosage units of 5 mg oxycodone for Mason.
Investigators concluded those purchases were highly unusual.
According to DOJ, Mason’s controlled-substance purchases were more than 16 times the national average for medical practitioners. During 2021 through 2023, she ordered more hydrocodone from MWI than any other individual customer, and in 2022 and 2023 accounted for all oxycodone dispensed by MWI to West Virginia veterinarians.
Those purchasing patterns shifted the focus of the investigation from the veterinary practice to the distributor.
The Order That Changed the Investigation
The settlement identifies one order in particular.
On Sept. 13, 2022, Mason ordered 300 tablets of 10 mg oxycodone.
According to federal investigators, MWI’s Suspicious Order Monitoring System flagged the purchase for review.
The company’s own Diversion Control Program requires suspicious orders to be investigated and specifically identifies oxycodone as a drug “especially susceptible to diversion” requiring heightened scrutiny. Internal policy also warns that the monitoring system “will fail if individuals clear orders without adequate investigation.”
Investigators alleged that an MWI representative opened the flagged order for review but released it the following day without substantial investigation. According to the settlement, MWI subsequently filled nine additional oxycodone orders, including one totaling approximately 1,300 pills, without questioning Mason or conducting additional due diligence.
The public settlement documents do not explain why the order was approved or what review occurred before it was released.
That unanswered question sits at the center of the case.
Investigators contend the company failed to act on information that its own system had already identified as warranting closer scrutiny.
A Warning for the Veterinary Supply Chain
Although the financial settlement itself was relatively modest, the case underscores the DEA’s expectations for every company that distributes controlled substances.
Under the Controlled Substances Act, distributors are required not only to ship medications but also to maintain systems capable of identifying suspicious orders and notifying DEA when appropriate.
The Mason investigation illustrates how enforcement can expand beyond an individual veterinary practice.
What began as a DEA inspection into one veterinarian’s recordkeeping ultimately became a broader examination of how controlled substances move through the veterinary supply chain — and whether distributors are fulfilling their own independent responsibilities to detect unusual purchasing patterns before medications reach the clinic.
The case also serves as a reminder that controlled-substance compliance extends well beyond prescribing decisions. Accurate inventories, dispensing logs, DEA Form 222 records and biennial inventories remain fundamental regulatory requirements, and deficiencies in those records can become the catalyst for investigations that reach far beyond a single practice.
