OKLAHOMA CITY, OK (WCMH) – An Oklahoma doctor is facing murder charges after several of her patients overdosed and died from multi-drug toxicity.

Dr. Regan Nichols is charged with five counts of second-degree murder in connection with the deaths of five of her patients. Court documents say Nichols knowingly prescribed controlled dangerous substances to the patients in dangerous quantities when there was no legitimate need.

“Our investigation has revealed that during a period of approximately five years, Dr. Nicholas prescribed extremely large quantities of controlled substances in suspect combinations, including the most abused and sought after prescription drugs on the street,” the probable cause affidavit reads. “During this same time period, ten (10) patients have died from overdoses of the very same drugs she was prescribing in massive doses.”

According to KFOR, investigators found five people dead after they were prescribed more than 1,800 opioid pills in the same month that they died. Three of them were prescribed an anti-anxiety drug, a muscle relaxer and an opioid pain reliever – a deadly combination.

Nichols lost her prescribing ability for controlled dangerous substances in 2015. According to data from the Oklahoma Bureau of Narcotics, Nichols prescribed in excess of 3 million dosage units of controlled dangerous substances between January 2010 and October 2014.

“The dangers associated with opioid drugs have been well documented, and most doctors follow strict guidelines when prescribing opioids to their patients,” said Oklahoma Attorney General Mike Hunter. “Nichols prescribed patients, who entrusted their well-being to her, a horrifyingly excessive amount of opioid medications. Nichols’ blatant disregard for the lives of her patients is unconscionable.”