Tirzepatide (Zepbound) weekly injection will be a new option for obesity...now that it’s available in Canada to promote weight loss.
Tirzepatide is the same ingredient in Mounjaro for type 2 diabetes. It works similarly to semaglutide (Wegovy), but it’s a dual agonist...working at two receptor types instead of just one.
These meds increase satiety and slow gastric emptying...which may lead to weight loss in people with or without diabetes.
When compared head-to-head, tirzepatide leads to an average of about 23 kg of weight loss compared to about 17 kg with semaglutide over about a year in patients without diabetes.
Think of these meds as more effective than other weight loss meds. For instance, liraglutide leads to roughly 5 kg of weight loss.
Also, data suggest that adding semaglutide 2.4 mg weekly for patients with overweight or obesity AND CV disease prevents 1 CV event for every 67 patients treated over about 3 years.
Results from a similar study with tirzepatide are due in 2027.
But it’s not all smooth sailing with these meds.
Tirzepatide or semaglutide commonly causes GI upset, especially during dose escalation. And both carry warnings for rare pancreatitis or gallbladder disease...and are linked to bowel obstruction.
Tirzepatide costs up to $820/month and semaglutide around $430. Many payers don’t cover these or require a prior auth...and high demand can cause shortages.
Plus patients may need to use these meds long term...since weight gain is common after stopping.
Expect your pharmacist to emphasize lifestyle changes (increased exercise, etc) first for weight loss.
Weight loss meds might be an option for patients with a BMI of 30 or more...or 27 or more plus a weight-related condition (diabetes, etc).
But the selection of which weight-loss med will be based on weight loss goals, comorbidities, cost and access, etc.
For instance, tirzepatide may be considered for patients with severe obesity, since it may lead to more weight loss...or semaglutide for patients with CV disease based on CV benefit.
Check sigs and Rx notes for titration instructions...since these meds are usually titrated slowly to minimize GI effects.
For example, expect tirzepatide to start at 2.5 mg subcut weekly and increase by 2.5 mg every 4 weeks...up to 15 mg/week as tolerated.
Pull in your pharmacist if you hear a patient complain of GI upset on these meds. Modest GI upset is expected...but severe pain can be a red flag for gallbladder issues or pancreatitis.
Refer to our resource, Weight Loss Products, for other considerations such as dosing, monitoring, and more.
- Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. N Engl J Med. 2025 Jul 3;393(1):26-36.
- Grunvald E, Shah R, Hernaez R, et al; AGA Clinical Guidelines Committee. AGA Clinical Practice Guideline on Pharmacological Interventions for Adults With Obesity. Gastroenterology. 2022 Nov;163(5):1198-1225.
- American Diabetes Association Professional Practice Committee. 8. Obesity and Weight Management for the Prevention and Treatment of Type 2 Diabetes: Standards of Care in Diabetes-2024. Diabetes Care. 2024 Jan 1;47(Suppl 1):S145-S157.
- Jastreboff AM, Aronne LJ, Ahmad NN, et al; SURMOUNT-1 Investigators. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022 Jul 21;387(3):205-216.
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021 Mar 18;384(11):989-1002.
- Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med. 2023 Dec 14;389(24):2221-2232.