TORONTO -- An Ontario mother is made by pharmacies after her son died from what she called a devastating "careless mistake."

Melissa Sheldrick's eight-year-old son Andrew was diagnosed with a sleep disorder called parasomnia and began taking medication for the problem in October 2013.

For a year and a half, Sheldrick refilled her son's prescriptions every two weeks at Floradale Medical Pharmacy, a compounding pharmacy in Mississauga, Ont., that dispensed the medication in liquid form.

On March 12, Sheldrick gave her son a dose from a new refill of his prescription before he went to bed. The next morning, she said her boy was found dead.

It was only four and a half months later that police told Sheldrick a coroner's report found Andrew died as a result of an overdose of a muscle relaxant, which was in his prescription drugs container instead of the sleep medication he typically took, she said.

"Not only now were we traumatized and grief-stricken, but we were angry. Really, really angry. To know that this was preventable, that it was a mistake. Somebody wasn't paying attention," Sheldrick said. "It's horrific."

Sheldrick has since filed a lawsuit against the pharmacy but is now also petitioning the Ontario government to pass legislation to mandate the use of error-tracking tools for dispensaries.

Ontario Health Minister Eric Hoskins said he's aware of the "tragic circumstances" of Andrew's death and said he's prepared to look at the issue.

"I will be looking specifically, in light of this tragic situation, to see if there's more that can be done in a transparent and accountable way," he said. "I will be working with the Ontario College of Pharmacists to see if there's more that can and should be done."

Hoskins added that he knew of only one province so far -- Nova Scotia -- that requires the reporting and public notification of pharmacy errors and said he would examine its experience with the issue.

The Ontario College of Pharmacists said it does not currently mandate the reporting of medication errors to an external body. But, a spokeswoman noted, such reporting of errors has always been recommended as a best practice.

"We take the dispensing of medications very seriously," said Lori DeCou. "There are safeguards in place to try to be as diligent as we can to minimize any risk of error from happening and we have procedures in place in the unfortunate event that incidents to happen for us to be able to learn from them.

The college is currently conducting its own investigation into Andrew's death, DeCou said, adding that the error in the case had been "self-reported" by the pharmacy practitioner.

DeCou pointed out that members of the public could also report incidents of errors directly to the college.

In Andrew's case, Sheldrick said her family is in the process of making a formal complaint to the college. She also plans on making a formal request to Ontario's coroner for an inquest into her son's death.

Police conducted an investigation into the matter but found no evidence of criminal negligence and no charges were laid, Sheldrick said.

The Institute For Safe Medication Practices then conducted their own investigation and is in the process of putting together a report on the procedures the pharmacy followed to prepare Andrew's medication.

For Sheldrick, pushing for change in the way pharmacies deal with errors is helping her deal with her devastating loss.

"I can't let this go, I don't want his death to be in vain. Something good has to come out of it," she said. "He was lost because of a careless mistake...pharmacies are not being held accountable."