Bartels' lifeless body was found later that day,court documents say. A medical examiner concluded that she died of multiple drug toxicity, another victim of the America's opioid epidemic.
But investigators say the 55-year-old Bartels was also a victim of Nichols, a pain management doctor who investigators concluded "either didn't know or didn't care what she was doing."
Nichols is charged with second-degree murder in the death of Bartels and four other patients, some of whom died just days after receiving large prescriptions from the doctor.
She was arrested Friday and released from Oklahoma County Jail on $50,000 bail.
She couldn't be reached for comment on Saturday. A number listed for Sunshine Medical Center was disconnected. Jail officials didn't know whether she had hired an attorney.
The doctor's arrest is part of a new and growing offensive in America's battle against the abusive use of opioids, which kill an average of 91 people a day, according to the Centers for Disease Control and Prevention.
Law enforcement agents aren't just going after drug dealers and Mexican cartels - they're also targeting pharmaceutical companies and doctors, who they say are irresponsibly flooding the nation with potent painkillers, and holding them responsible for overdose deaths.
"Nichols prescribed patients, who entrusted their well-being to her, a horrifyingly excessive amount of opioid medications," Oklahoma Attorney General Mike Hunter told the Associated Press on Friday as his office announced the doctor's arrest. "Nichols' blatant disregard for the lives of her patients is unconscionable."
Opioids killed more than 33,000 Americans in 2015, according to the CDC. Since 1991, the number of opioid overdose deaths has quadrupled. In 2014, according to the Agency for Healthcare Research and Quality, 1.3 million Americans were hospitalized for opioid-related issues.
And prescription opioids are a primary driver, and prosecutors increasingly have gone to the source to stop abuse. InFebruary 2016, another doctor, Hsiu-Ying "Lisa" Tseng, was sentenced to 30 years to life in prison after three of her patients fatally overdosed, according to the Los Angeles Times.
Prosecutors said Tseng made millions from overprescribing opioids to drug-addicted patients.
And lawyers for the Cherokee Nation in Oklahoma have sued the nation's top six drug distributors, according to The Washington Post's Scott Higham and Lenny Bernstein. The suit says the pharmaceutical companies are profiting from the epidemic and "decimating communities across the nation's 14 counties in the state."
Last month, seven counties in West Virginia, a state that has the highest prescription drug overdose rate in the nation, filed suits against many of the same corporations, according to Higham and Bernstein.
A lawsuit by the state of Missouri against pharmaceutical giants strikes a similar tone.
Missouri Attorney General Josh Hawley said the companies have used bogus science to mislead patients about just how addictive opioids are, according to The Washington Post's Katie Mettler. As a result, the companies have "profited from the suffering of Missourians."
The lawsuits have different aims, although attorneys in the Missouri case say they want state legislatures to more closely monitor prescription drug use.
Oklahoma's attorney general has been trying to paint Nichols in the same light.
Nichols prescribed more than 3 million doses of controlled dangerous drugs from 2010 through 2014, according to court documents, including "irrational" and dangerous combinations of drugs that led to five deaths.
On March 24, 2010, for example, Debra Messner received a prescription for 450 pills - the same cocktail of Hydrocodone, Xanax and Soma and died six days later of acute drug toxicity, according to court documents. A doctor contracted by the Drug Enforcement Administration to review her case file found that there was "no need for the quantity or combination" of those drugs.
Lynette Nelson was evaluated by Nichols once, a few days before Christmas in 2008. Still, over the next four years, Nelson was prescribed so many potent drugs from Nichols's clinic that investigators were baffled that she didn't die sooner.
She was found dead on March 1, 2012, five days after getting her final prescription of Xanax filled.
In the probable cause affidavit, the doctor contracted by the DEA to examine the dead patients' files concluded that because of Nichols's "lack of the use of the basic fundamental safeguards, patients suffer and very well may end up paying the ultimate price as all ten of these patients did."
