Mr Stewart does not know which is more controversial these days, OxyContin or pot.
He guesses the average person would give “a bigger negative” to the powerful and controversial painkiller that has been linked to the opioid overdose and addiction epidemic in the US and Canada.
“There is a lot of anti-opioid sentiment,” he says, delicately. “And certainly based on the social disruption that we’ve seen it’s understandable.”
In the US, an estimated 1.9 million Americans were addicted to prescription opioid painkillers in 2014. Accidental overdoses from prescription painkillers quadrupled between 1999 and 2012. In 2014, drug overdoses were the leading accidental cause of death south of the border, driven by prescription opioids.
North of the border, some 15% of Canadians have an opioid painkiller prescription and 2% of those report abusing the drug.
But Mr Stewart has turned his attention elsewhere. He left Purdue Pharma in 2013 and is now a co-founder of Emblem, a medical marijuana company based in Paris, Ontario.