A critical-care doctor in Ohio accused of ordering overdoses of the opioid painkiller fentanyl in the deaths of 25 hospital patients has sued his former employer for defamation, according to a report.

Dr. William Husel, who was indicted in June on 25 counts of murder and has pleaded not guilty, argued that he did nothing wrong and did not deviate from hospital policy on end-of-life care.

The doctor, whose license to practice was suspended in January by the State Medical Board of Ohio, filed the lawsuit Thursday in Franklin County against the Columbus-area Mount Carmel Health System and its parent organization, Trinity Health Corp.

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Mount Carmel Health System said in an email statement to Fox News Monday afternoon: "Allegations such as these are unfounded. We completed an extensive review of patient care provided by Dr. William Husel and stand by our decisions. Mount Carmel’s focus continues to be on caring for our patients."

Trinity Health Corp. added in an email statement to Fox News Monday afternoon: "Allegations such as these are unfounded. We completed an extensive review of patient care provided by Dr. William Husel and stand by our decisions. Trinity Health's and Mount Carmel’s focus continues to be on caring for our patients."

In the lawsuit, Husel claims that patients died from their illnesses, not the administration of the powerful painkiller fentanyl ordered by him.

Husel also claims he received no formal training on hospital procedures from Mount Carmel when he was hired in 2013 as a critical-care physician and that he received a doctor of the year award in 2014.

Husel’s lawsuit seeks more than $50,000 in damages, along with attorney fees.

William Nusel, facing 25 counts of murder for his role in the deaths of hospital patients said in a defamation lawsuit filed against the hospital system he worked for that he did nothing wrong and did not deviate from hospital policy in providing end-of-life care. (AP Photo/Kantele Franko, File)

The Franklin County Prosecution’s Office said in a statement that Husel ordered that patients receive doses of fentanyl "in various amounts between 500 and 2,000 micrograms ... that shortened their life and hastened or caused their death."

The suspicious deaths occurred at Mount Carmel and St. Ann’s Hospitals in Columbus between Feb. 11, 2015, and Nov. 20, 2018, according to the statement.

Husel was fired from the Columbus-area Mount Carmel Health System in December 2018 and stripped of his medical license when allegations against him began to surface and an internal investigation by the hospital uncovered his fatal prescriptions.

More than two dozen wrongful-death lawsuits have been filed against Husel and the hospital system, some of which have been settled by the hospital for hundreds of thousands of dollars, according to the Associated Press.

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Mount Carmel has admitted that Husel wasn't removed from patient care until four weeks after concerns about him were raised last fall and that three patients died during that gap after receiving the excessive doses he ordered.

The Associated Press contributed to this report.