Liver specialists and drug safety experts are “disappointed” with Health Canada for not going further to address safety concerns around acetaminophen, the ubiquitous painkiller found in Tylenol and hundreds of other products.

On Thursday, Health Canada announced new labelling rules for acetaminophen, stemming from a safety review published last year.

The changes include clearer instructions that emphasize the importance of using the lowest effective dose and heeding the maximum daily dose — defined by Health Canada as 4 grams per day, or eight tablets of extra-strength acetaminophen.

Packages will now have to include the words “contains acetaminophen” in bold, red text, as well as warnings not to take acetaminophen products for more than five days to treat pain, or three days for fever.

They will further warn Canadians not to mix acetaminophen with alcohol if they consume three or more drinks per day. Children’s liquid products will also now be required to include calibrated dosing devices.

The changes are effective immediately for any new acetaminophen products that come onto market. Drug companies that already have acetaminophen products on store shelves have 18 months to update their labels.

Health Canada’s announcement comes two-and-a-half years after the Star started investigating acetaminophen’s safety profile in Canada.

Acetaminophen is extremely safe when taken as directed, and more than four billion doses are sold to Canadians every year.

But larger amounts — especially when combined with alcohol — can be dangerous and acetaminophen is currently Canada’s leading cause of serious liver injuries.

Drug safety experts have long called for tighter rules around acetaminophen — but Thursday’s changes, some say, don’t go far enough.

“It’s underwhelming,” said Dr. David Juurlink, a drug safety researcher with Sunnybrook Health Sciences Centre. “It’s difficult to argue that any of the measures that they are implementing are bad; they’re all good ideas. But they’re not going to accomplish very much.”

Acetaminophen is one of Canada’s oldest and most popular painkillers, found in 445 products currently sold to Canadians — everything from Tylenol (the brand that popularized the drug) to NyQuil, NeoCitran and prescription drugs like Percocet. The drug can be easily purchased at any corner store or gas station, sometimes in 100 or 200-pill quantities.

But drug safety experts say the painkiller, if introduced today, probably wouldn’t be approved as an over-the-counter drug by modern-day regulators.

This is because acetaminophen has an alarmingly “narrow therapeutic window” — meaning the dose that hurts is dangerously close to the daily dose recommended on pill bottles.

While doctors have an effective antidote for treating overdoses, patients who don’t realize they’ve overdosed — or wait too long before seeking help — can suffer serious or fatal liver damage.

In September 2015, the Star obtained an internal report from drug manufacturer Johnson & Johnson, the makers of Tylenol, which found that between 2000 and 2011, an average of 68 Canadians died every year because of acetaminophen.

The Star also obtained internal Health Canada reports, in which experts urged the regulator to lower the drug’s daily recommended dose from four grams to 2.6 grams.

Other recommendations included restricting bottle sizes, removing acetaminophen from opioid combination products, and requiring a prescription for “high dose” products like Extra Strength Tylenol.

None of these measures were a part of Health Canada’s announcement on Thursday.

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According to senior medical advisor, Supriya Sharma, this is partly because new research has since emerged, casting doubt over the effectiveness of reducing acetaminophen package sizes to prevent suicide attempts.

Three technical discussions were also held following the 2015 acetaminophen safety review, which included mostly industry groups and drug manufacturers, as well as patient groups.

Health Canada “heard very strongly” from patient groups like the Arthritis Society, which opposed limiting the daily maximum dose or restricting access to extra-strength formulations of acetaminophen, Sharma said.

Industry groups were also opposed to such changes.

“This was the most extensive consultation on the safety of an over-the-counter drug I’ve seen in 30 years,” said Gerry Harrington, vice president of policy with Consumer Health Products Canada, which represents over-the-counter drug makers. “And the outcome, I think, reflects exactly the feedback (Health Canada) got. I think it’s the right outcome for consumers.”

But Dr. Constantine Karvellas disagrees. At the University of Alberta Hospital, the critical care physician is tracking acute liver failure cases and roughly 75 per cent are caused by acetaminophen.

He considers acetaminophen-related liver injuries a series public health problem and questions what kind of impact the labeling changes will have.

“I’m a little bit disappointed,” Karvellas said. “I would have liked to have seen a lowering of the maximum daily dose, as well as more inquiry into the possibility of limited packaging or limited sales.”

For Dr. Joel Lexchin, a drug safety researcher and professor emeritus with York University, he believes these latest changes are a good start.

But the drug safety researcher is “disappointed” not to see stricter rules around how acetaminophen is advertised. He would also like to see reductions in packet sizes and daily dosages.

Lexchin voiced these opinions during Health Canada’s technical discussions, which he participated in last year. But he’s not overly surprised to see that Health Canada chose not to adopt the more drastic proposals.

“I’m not discounting what they’ve done but I think they could have done a lot more,” he said. “Overall, when it comes to drug safety, Health Canada has a culture of slow incremental change. They’ve never taken any serious dramatic steps in improving drug safety.”