Joanna Bertrand, Donna Bertrand's sister, said Dr. Alan Redekopp should have heeded warnings from police that her sister was likely selling drugs. ((CBC))

A Brockville, Ont., doctor admits he kept increasing a patient's dosage of an addictive narcotic despite warnings that she was likely selling the drugs.

Donna Bertrand, 41, died of a drug overdose in November 2008, just days after 19-year-old Dustin King also died of a prescription drug overdose in the same Brockville apartment.

An inquest is being held into both deaths in an attempt to stop similar incidents.

Dr. Alan Redekopp began treating Bertrand 13 months before her death, prescribing what he called a high dose of OxyContin to treat her chronic back pain. Bertrand kept requesting more and, by the time she died, Redekopp had increased her daily amount by more than 10 times — up to 1,440 mg a day.

He also wrote new prescriptions for her on several occasions when she said her pills had been stolen.

Redekopp was warned by police, a pharmacy and another doctor that she was likely selling the drug. At the inquest, he said he had concerns but believed her when she said she wasn't dealing.

Joanna Bertrand, Donna's sister, said Redekopp should have done more research.

"He should have gotten the police reports, in my opinion, to see exactly what it did entail — so that he could see himself. He just immediately wrote out another script," she said. 

Brenda Wiles, King's mother, told CBC News she believes Redekopp was neglectful. King died of an overdose despite having no prescription.

"The should'ves, and could'ves, and 'in retrospect,' it doesn't do anybody justice right now," she said. "There may be two people still living if there had been better caretaking."

As a result of Bertrand's death, Redekopp faces a disciplinary hearing before the College of Physicians and Surgeons of Ontario this fall. In the meantime, he has been prohibited from prescribing opiates such as OxyContin.