One of the most commonly used pain relievers on the market is also the leading cause of all serious liver injury, Health Canada says, prompting the department to roll out updated labelling standards for acetaminophen on Thursday.

The changes include instructions on packages to encourage the use of the lowest possible dose and warnings not to use the products for more than five straight days for pain or three days for a fever.

The department also recommends that adults not exceed the recommended daily dose of 4,000 mg for adults — the equivalent of 12 regular Tylenol tablets or eight extra-strength pills.

Label changes apply immediately for companies seeking to introduce new products, but companies already on the Canadian market will have 18 months to comply.

Acetaminophen presents a unique challenge for health care providers because it is so commonly used, Health Canada chief medical adviser Dr. Supriya Sharma said Thursday.

“It can be safely used if people are following the labels and the directions for use,” she said.

“However, at the same time, is a product that is responsible for the most number of cases of acute liver failure in Canada … I can’t think of another product that is in this category.”

The challenge for the department, practitioners and patients is to balance benefits with the risks, Sharma added.