 -- The Oklahoma attorney general has charged a 67-year-old doctor with five counts of second-degree murder, accusing her of prescribing excessive amounts of "dangerous" medications to patients "without legitimate medical need" and causing the deaths of at least five patients.

The charges were filed in the District Court of Oklahoma County against Regan Nichols, an osteopathic physician in Midwest City, Oklahoma, on Friday morning. Oklahoma Attorney General Mike Hunter has accused Nichols of being involved in five deaths, all of which occurred between 2010 and 2013, according to the probable cause affidavit. The patients who died ranged in age from 21 to 55.

Reports from the Oklahoma Medical Examiner's office stated that all five of the deaths were the result of multi-drug toxicity, according to a press release from the attorney general's office.

Three of the individuals were allegedly prescribed "deadly" and "addictive" combination "cocktails," which included Hydrocodone, Oxycodone, Alprazolam and Carisoprodol, according to the affidavit, which stated that all of the prescriptions were signed by Nichols.

Nichols also allegedly prescribed more than 3 million dosage units of controlled dangerous substances between Jan. 1, 2010 and Oct. 7, 2014, based on data gathered by agents with the Oklahoma Bureau of Narcotics and Dangerous Drugs Control's Prescription Monitoring Program, according to the affidavit.

The attorney general also alleged that 10 of Nichols' patients died from overdoses during that time period. Nichols is being charged with five counts of second-degree murder.

After the September 2015 hearing, the Oklahoma State Board of Osteopathic Examiners stripped Nichols of her ability to prescribe controlled dangerous substance for five years, according to court documents. She then voluntarily surrendered her credentials.

During the 2015 hearing, when asked if she thought she overprescribed, Nichols responded that she believed the patients had developed a tolerance to their medications.

Earlier that year, in a March 2015 interview with the Oklahoma Bureau of Narcotics and Dangerous Drugs Control, Nichols told investigators that she would "fire" or dismiss patients who did not comply with the office's drug screen policies, but she would "unfire" them or give them second and third chances if the abused drug was marijuana, according to the affidavit.

An Oklahoma County judge issued a warrant for Nichols' arrest on Friday. She will be held on $50,000 bond.

"Dr. Nichols prescribed extremely large quantities of controlled substances in suspect combinations, including the most abused and sought after drugs on the street, to numerous patients with very little medical examination or the establishment of a valid doctor-patient relationship and for no legitimate medical need," the probable cause affidavit states.

In a statement, Hunter said that "Nichols' blatant disregard for the lives of her patients is unconscionable."

"The dangers associated with opioid drugs have been well documented and most doctors follow strict guidelines when prescribing opioids to their patients," Hunter said. "Nichols prescribed patients, who entrusted their well-being to her, a horrifyingly excessive amount of opioid medications."

Nichols was not on law enforcement's radar until May 2014, when a concerned former patient reported her to authorities, according to the affidavit. The Oklahoma Bureau of Narcotics and Dangerous Drugs Control said it began investigating her in October 2014.

Nichols was booked into the Oklahoma County Jail Friday afternoon on $50,000 bond. As of Friday afternoon, Nichols had not yet been arraigned, according to the Oklahoma County Court Clerk.

ABC News could not immediately reach Nichols for comment, and it is unclear if she retained an attorney. Calls to her medical office were not returned and the phone there appeared to be disconnected.