The long awaited approval of tirzepatide for weight management (Zepbound) in Canada has finally happened! Tirzepatide, which has been approved in Canada as a diabetes medication (Mounjaro) since 2022, received Health Canada approval for weight management this week. (Note that in some countries, tirzepatide is under the brand name Mounjaro whether it’s for diabetes or for obesity. In countries like USA and Canada, it’s called Mounjaro for diabetes, and Zepbound for obesity.)
Tirzepatide, which is a dual GIP/GLP1 receptor agonist, is now approved for weight loss and weight maintenance, in addition to healthy lifestyles, in people with a BMI of 30 or greater, or BMI of 27 or greater with at least one weight-related health issue. This approval is based on a robust program of clinical trials, showing an average weight loss of up to 20.9% (almost 50lb) in the largest trial at 72 weeks, sustained weight loss at 3 years, and benefits to many weight-related health issues, including blood sugar and blood pressure improvements, prevention of diabetes, and improvements in sleep apnea, MASH (formerly ‘fatty liver disease’), and heart failure with preserved ejection fraction.
The dosing of tirzepatide for weight loss or type 2 diabetes is identical. It is escalated gradually, starting at 2.5mg weekly, increasing by 2.5mg no faster than every 4 weeks, towards treatment doses of 5mg, 10mg, or 15mg weekly. Note that it is a-ok to slow the dose increase to a pace that fits you/your patient. While it is off-label, some people may find that an interim dose (eg 2.5mg, 7.5mg, 12.5mg) work best for them, and that’s ok too. Remember that weight management medication should be titrated as needed, as tolerated, and as appropriate to each individual. With highly effective weight loss medication, it’s important to ensure you/your patient is getting adequate nutrition (see here and here), and not losing excessive weight (see here and here). Zepbound is approved in a KwikPen in Canada, and will not be available in the vial and syringe format.
The most common side effects of tirzepatide are gastrointestinal, including nausea, diarrhea, and vomiting, which are mostly mild to moderate in nature, and mostly during dose escalation. Injection site reactions were seen in 8% of people taking Zepbound, vs 1.8% with placebo. As for other GLP1 receptor agonists, there is a low risk of gallbladder inflammation and gallstones. There was no increased risk of pancreatitis in the weight management trials, though there was a slightly increased risk in the diabetes studies.
As blogged previously, remember that other medications may need to be adjusted at the start and/or as you increase the dose and/or with weight loss, for example medications for blood pressure, blood sugar (diabetes), thyroid hormone, and others. Absorption of the birth control pill is reduced by tirzepatide likely due to slowing of the gastrointestinal tract, which is most prominent during dose escalation. As such, the product monograph recommends an alternative form of contraception, or adding a barrier method of contraception for 4 weeks after initiation and for 4 weeks after each dose escalation.
BOTTOM LINE: Tirzepatide (Zepbound) is now approved for weight management in Canada. It is a highly effective medication for weight loss, and can improve a number of weight-related health issues. We now have 6 medications approved for weight management in Canada, with more sure to be added to that list in coming years!
Disclaimer: I am/have been an investigator in clinical trials of tirzepatide. I receive honoraria as a continuing medical education speaker and consultant from the makers of tirzepatide (Eli Lilly).
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