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Writer's pictureEmily Lawson

Mounjaro and Metformin: A Head-to-Head Comparison

A box of Mounjaro (tirzepatide) injection sits beside a blister pack of Metformin 500 mg tablets on a table. The Mounjaro box is labeled for subcutaneous use and includes four single-dose prefilled pens.

Mounjaro (tirzepatide) and metformin are two prominent diabetes medications used to manage blood glucose levels in people with type 2 diabetes. Let's dive into their efficacy, mechanism of action, side effects, NHS availability, cost differences, and clinical trial results that compare both medications for diabetes and weight management.


Efficacy


In clinical trials, Mounjaro has demonstrated superior efficacy in reducing blood glucose levels. Participants taking Mounjaro experienced an average A1C reduction of 2%, with many achieving A1C levels below 7%. Comparatively, metformin typically provides an average A1C reduction of 1% to 1.5%.


Additionally, Mounjaro has shown significant results in weight management. Participants in clinical trials experienced up to 15% body weight reduction, whereas metformin is considered weight-neutral.


Mechanism of Action


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Mounjaro is a dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) agonist. It mimics the action of these gut hormones to enhance insulin secretion, reduce glucagon levels, and slow gastric emptying, thereby controlling blood sugar levels and promoting weight loss.


On the other hand, metformin belongs to the biguanide class of drugs. It decreases hepatic glucose production and enhances insulin sensitivity. This makes your body more efficient at utilizing insulin and lowers the amount of glucose absorbed in the intestines.


Side Effects


Both medications are associated with gastrointestinal (GI) issues. Mounjaro's common side effects include nausea, diarrhea, loss of appetite, vomiting, and constipation. More serious side effects might include pancreatitis and gallbladder disease.

Metformin also leads to GI problems such as diarrhea, nausea and vomiting, and occasionally causes low B12 levels and weight loss. Rare but severe risks include lactic acidosis, which necessitates immediate medical attention.


NHS Availability


Mounjaro (tirzepatide) is approved for use in the NHS as of October 2023, following final guidance by NICE. This followed clinical trials demonstrating its efficacy and cost-effectiveness for adults with poorly controlled type 2 diabetes. Metformin, being a longstanding and cost-effective treatment, is widely available and remains a go-to choice for many healthcare providers.


Cost Differences


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Mounjaro, currently available only as a brand-name medication, tends to be more expensive compared to metformin, which is available as a lower-cost generic. This makes metformin a more economical option for many patients, although Mounjaro may offer better efficacy and weight management benefits in certain cases.


Clinical Trial Results


Clinical trials have shown that Mounjaro significantly reduces blood glucose and body weight compared to other treatments like semaglutide, insulin therapy, or a placebo. 81% to 97% of participants reached better glucose control, and 54% to 88% achieved a 5% or greater reduction in body weight.


In contrast, while metformin effectively lowers A1C and potentially modestly reduces weight, its impact on body weight is not as pronounced as Mounjaro's.


Overall, Mounjaro provides notable advantages in blood glucose control and weight reduction but at a higher cost. Metformin continues to be a reliable and cost-effective first-line option, particularly for patients where cost and simple oral administration are significant considerations.


Conclusion


Both Mounjaro and metformin offer substantial benefits for managing type 2 diabetes, albeit through differing mechanisms and with varying side effects. Mounjaro stands out for its dual action on GLP-1 and GIP and significant weight loss benefits, making it a potent option for those struggling with both diabetes and obesity. Metformin, tried and true, remains economically accessible and effective at controlling glucose levels for a broad patient demographic.


The choice between Mounjaro and metformin should be individualized, taking into account the specific needs, side effects, and economic considerations of each patient. Consulting with healthcare providers will ensure that the chosen medication aligns well with lifestyle and therapeutic goals.

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