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It’s finally here! Approved in November 2022, tirzepatide (trade name Mounjaro) is now available at pharmacies in Canada. We have been waiting a year due to the global shortage, in the context of unprecendented demand. As blogged previously, tirzepatide is a GIP/GLP1 receptor agonist that is approved as a treatment of type 2 diabetes. It is very effective for improvement in glucose control, and also very powerful to help people with type 2 diabetes and obesity lose weight. Across the SURPASS type 2 diabetes clinical trial program, A1C (diabetes report card) reduction ranged from -2.1 to -2.6% with the 15mg weekly dose, a reduction of a magnitude that has not been seen in clinical trials of other approved diabetes medications, and superior to both semaglutide 1mg (Ozempic) and insulin comparators. Weight reduction ranged from -9.5% to -12.5% weight loss across the trials with tirzepatide 15mg weekly, again a magnitude not seen in clinical trials of any other approved diabetes medication. Notably, weight loss with tirzepatide 15mg was double that seen in head-to-head comparison with semaglutide 1mg (-12.4% and -6.2%, respectively).
While initially approved in a pen device for very simple injection, due to a global shortage of the pen devices, tirzepatide is available in Canada in a vial-and-syringe format. This means that, just like in the old days of insulin, tirzepatide will need to be drawn up from a vial and then injected subcutaneously (under the skin). As the dose of tirzepatide is escalated gradually (starting at 2.5mg weekly, increasing by 2.5mg every 4 weeks towards treatment doses of 5mg, 10mg, or 15mg weekly), each dose level will have its own vial. You draw up 0.5mL, which is almost the entire vial, for each injection (one vial per injection). Do not split a dose of tirzepatide from a vial into smaller doses, because the vial does not contain a preservative, and thus the contents must be used as soon as the needle is pushed through the rubber stopper the first (and only) time. The needle required (28-31 gauge) is just a tiny bit thicker than the Ozempic needle (32 gauge) , because the needle has to be strong enough to penetrate the rubber stopper on the vial without bending the needle. As per the Canadian FIT guidelines for injectable medications for diabetes, the needle length should be 6-8mm (a little longer than the 4mm Ozempic needle). But it’s still very small!
The makers of tirzepatide have a website to support the tirzepatide journey, for patients and health care providers. There are also patient instructions on page 44-49 of the product monograph. There is a small discount offered by the manufacturers for people with type 2 diabetes, which your pharmacist can help you out with.
Potential side effects of tirzepatide are in keeping with the GLP1 class. The most common side effects include nausea, diarrhea, and vomiting, are mostly mild to moderate in nature, and mostly during dose escalation. As for other GLP1 receptor agonists, there is a low risk of gallstones, and a very low risk of pancreatitis. Also, a note that 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.
Tirzepatide has demostrated impressive efficacy as a weight management medication as blogged previously, with an average -20.9% weight loss seen with the 15mg dose in people with obesity without type 2 diabetes in the SURMOUNT1 trial. Tirzepatide is not (yet) approved as a weight management medication.
BOTTOM LINE: Tirzepatide is an important new treatment option for people with type 2 diabetes, with impressive efficacy to improve blood sugars and lower weight. While the vial-and-syringe administration requires a few extra steps to inject, it is not complex, and can be easily adopted by most people with a little support and teaching from pharmacists, diabetes educators, or physicians. It is always in the hands of the patient to decide if they are comfortable with the vial and syringe administration, but I predict that given the impressive efficacy of Mounjaro, most will be more than willing.
Disclaimer: I am/have been an investigator in clinical trials of tirzepatide and semaglutide. I receive honoraria as a continuing medical education speaker and consultant from the makers of tirzepatide (Eli Lilly) and semaglutide (Novo Nordisk).
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