A Louisville pain doctor is among 53 physicians, pharmacists and other medical professionals charged Wednesday with health care fraud in the biggest sweep of its kind in U.S. history.

Dr. Christopher Nelson, with Louisville's Bluegrass Pain Consultants, has been indicted on federal charges of teaming with a pharmacy to defraud Medicare and Tricare, a health care program for military veterans, by inflating drug costs. Nelson is accused in a kickback and bribe scheme to funnel customers to Assured Rx for drugs used for pain, including controlled substances, according to the indictment unsealed this week.

Bluegrass clinics in Louisville and La Grange closed amid the investigation.

Nelson was arraigned Wednesday afternoon in federal court and entered a plea of not guilty.

His attorney, Scott C. Cox, declined to discuss the case. "We look forward to receiving discovery from the government, reviewing it and going forward from there," he said referring to any evidence prosecutors have in the case.

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Several defendants are charged with teaming with Nelson in the alleged scheme, including Assured Rx — a home delivery pharmacy based in Clearwater, Florida.

Assured Rx's attorney, Lee Bentley, could not be reached Wednesday at his office in Tampa, Florida. Calls Wednesday to a supervisor with the company were not been returned.

Indictments represent only the side of prosecutors, and defendants are presumed innocent unless convicted.

The pharmacy giant is accused of paying bribes to the Louisville doctor and, in turn, most of the Bluegrass clinics' patients were referred to the pharmacy for drug products — with reimbursements from Medicare and Tricare, prosecutors allege in the indictment.

"What we're charging today, what we will continue to investigate and charge, are examples of criminal medical conduct that places patients at risk," said Russell Coleman, U.S. attorney for the Western District of Kentucky.

Nelson controlled ETN, LLC, a company set up in his relative's name, which pocketed more than $225,700 during a five-month period in 2015, the indictment alleges. Nelson is accused of accepting another $282,000 in kickbacks from July 2015 to Jan. 4, 2016, through a company set up by one of his employees who is a close friend.

Another one of the doctor's relatives and his employee-friend became paid marketing representatives for the special medication. Prosecutors say insurance companies were billed for medication covered by government insurance programs.

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Nelson also is accused of paying bonuses to Bluegrass Pain Consultants nurse practitioners and physician assistants based on the number of drug products they prescribed to patients that were filled by Assured Rx.

The clinic's doctors would sign these prescriptions or a clinic employee would sign or stamp one of the doctors' names on the Assured Rx order form, the indictment alleges.

Federal agents were seen raiding Bluegrass Pain Consultants clinics in June but remained mum on the investigation.

While local police and agents with the FBI and Drug Enforcement Administration were sorting through medical records at the Worthington clinic on Champion Farms Drive, next to the Montessori School of Louisville, a chronic pain patient leaned on a cane and asked what was going on.

She told a reporter the doctors are nice and have provided needed medication for seven years.

Coleman and Rob Duncan, Kentucky's two U.S. attorneys, announced the indictments against the Bluegrass doctor and others Wednesday in Cincinnati as part of the Appalachian Regional Prescription Opioid Strike Force initiative. It unites prosecutors and data analysts trained in these types of cases with several federal agencies — including the FBI, DEA, postal service officials, the IRS and others.

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A special strike force from the U.S. Department of Justice, which led the investigation, began making arrests in five states early Wednesday, while others were issued citations, according to a joint news conference Wednesday morning in Cincinnati.

Most of the defendants face charges of unlawful distribution of controlled substances involving prescription opioids.

Dr. Ijaz Mahmood, who operates a clinic in Elizabethtown, also was indicted on controlled substance and health care fraud charges. He is accused of authorizing prescriptions for drugs — including controlled substances — at times when he wasn't even in the country. Prosecutors allege he provided presigned, blank prescriptions to office staff so they could approve narcotics when he wasn't around. He also directed employees, including some who weren't licensed to practice medicine, to perform medical services on patients, according to allegations in the indictment.

Mahmood told a reporter he didn't want to discuss the charges.

Five people were indicted in the Eastern District of Kentucky, including three doctors and a dentist who were charged in connection with several health care fraud or controlled substance schemes or both. They include: Dr. Mohammed A.H. Mazumder, with offices in Franklin and Floyd counties; Dr. Scotty R. Akers, from the Pikeville area; Dr. Denver D. Tackett, a McDowell dentist; and Dr. Sai P. Gutti, who has offices in Pikeville, Harold, Paintsville, Whitesburg and Belfry.

Coleman, based in Louisville, said more health care fraud investigations are underway in his district and to expect charges in late spring or early summer.

Reporter Beth Warren: bwarren@courier-journal.com; 502-582-7164; Twitter @BethWarrenCJ. Support strong local journalism by subscribing today: courier-journal.com/bethw.