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Understanding Mounjaro: The UK's New Weight Loss Injection

Pharmacy2U Team | minute read
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In recent months, weight loss medications have been a talking point around the world as more medications are approved for sale and prescription. Mounjaro is one of these medications and following its licensing by the Medicine and Healthcare products Regulatory Agency (MHRA) in November of 2023, more and more people are now being prescribed it for support with their weight loss journey. 

Here we’ll take a look at the history of Mounjaro and discuss the science behind the drug as well as the clinical data on its biological effects on the body, from weight loss to side effects. We’ll also share some diet and lifestyle advice to improve the medication’s efficacy.

What is Mounjaro?

First approved for use in treating type-2 diabetes in 2022, Mounjaro is the brand name for tirzepatide; a long-acting GIP-analogue that activates the GLP-1 and GIP receptors, improving blood sugar control and slowing the movement of food through the stomach. 

While other well-known brands of weight loss medication such as Wegovy and Saxenda target just the GLP-1 receptors, Mounjaro is the first medication of its kind to combine this type of medication with the GIP agonist. 

This combination has been shown to boost the weight loss potential in users of Mounjaro, with tirzepatide showing an average weight loss of 17.8% compared to 12.4% for semaglutide users in clinical studies. 

The history of Mounjaro

While semaglutide has been around since the 1980s, Mounjaro is a much newer drug. First patented by Eli Lilly in late 2016, tirzepatide offered some improvement in the treatment of type-2 diabetes compared to semaglutide. However, the impact of tirzepatide on chronic weight management showed significant improvement compared to these older medication types.

Tirzepatide trails

As with any drug made available for human use, Mounjaro has been trialled and tested for safety and efficacy. In two randomised trials, tirzepatide was tested for weight reduction in 2,519 receiving the drug in once-weekly doses ranging from five to 15mg with a control group of 958 participants receiving a once-weekly placebo injection. 

After 72 weeks, all participants taking doses of tirzepatide experienced a significant reduction in weight compared to those receiving the placebo. The larger of the two trials saw those receiving the highest dose of Mounjaro lose 18% of their body weight on average. 

Tirzepatide trails

As with any drug made available for human use, Mounjaro has been trialled and tested for safety and efficacy. In two randomised trials, tirzepatide was tested for weight reduction in 2,519 receiving the drug in once-weekly doses ranging from five to 15mg with a control group of 958 participants receiving a once-weekly placebo injection. 

After 72 weeks, all participants taking doses of tirzepatide experienced a significant reduction in weight compared to those receiving the placebo. The larger of the two trials saw those receiving the highest dose of Mounjaro lose 18% of their body weight on average. 

Mounjaro side effects

While the results from Mounjaro's use for weight loss in clinical trials speak for themselves, studies have shown that there is a moderate risk of side effects with the use of the drug. Gastrointestinal adverse effects can be seen in many participants, such as diarrhoea, nausea, and vomiting, however, these side effects often subside quickly and can be easily managed.

How to take Mounjaro

A healthcare professional will prescribe users a specific dosage of Mounjaro. You should not take more than this recommended amount. This medication is taken as an injection once a week. 

Mounjaro is administered via injection into the upper arm, thigh or stomach. It can be administered by the user into the thigh or stomach area, however help from an additional person is needed to inject Mounjaro into the upper arm safely. 

When administering a Mounjaro injection, you must not inject directly into muscle or veins, and make sure you avoid using the same injection point as in previous weeks. 

It is common to experience minor irritation at the injection site. This might present as redness and itching however these symptoms often go away quickly with proper aftercare. If you find that the irritation is escalating, causing you severe discomfort, or looks to be infected, you should speak to your health care professional.

What is the best diet for Mounjaro?

With all weight loss aides like Mounjaro, these drugs are designed to be used in conjunction with a healthy diet and regular exercise to achieve the best results. A balanced diet is a great way to optimise the effects of the drug. 

A healthcare provider will be able to offer dietary advice based on each case, however, generally a good place to start with diet changes is to cut down on high-fat foods and increase intake of fresh fruits and vegetables as well as protein and whole grains. 

Because Mounjaro makes users feel fuller for longer by slowing down the rate at which meals move through the stomach, eating balanced meals that are around half the size of meals users would previously eat will help to get the most from this process. Smaller meals help to avoid gastrointestinal side effects and can help to reduce the size of the user’s stomachs which increases the longevity of the drug’s effects.

What exercise should I do on Mounjaro?

Regular exercise remains a key element of any weight loss journey, even if medication such as Mounjaro is used. It is recommended to do between 30-60 minutes of exercise each day for a healthy lifestyle, however, those who are looking to lose weight should consider increasing their time spent exercising to achieve the best results. This might look like:

  • Aerobic exercise such as walking, running, swimming and cycling

  • Weight training to build resting metabolic rate

  • Flexibility and balance training with yoga and stretches

Because Mounjaro is a prescription-only medication for those with a BMI indicating being overweight or obese, it might be easiest for users to start with low-impact exercise for shorter times and more often. For example, taking regular brisk walks might be a better way to get impactful exercise than trying to do long or fast runs straight away. 

Communicate with your healthcare professional

Starting the weight loss journey with Mounjaro is a personal process. Should you have any questions regarding the drug or about any effects you are experiencing from taking Mounjaro, talking to your healthcare professional is always advised. Your GP can offer you advice on dosage as well as lifestyle changes like diet and exercise. 

If you find yourself experiencing serious side effects when taking Mounjaro, contact your healthcare provider, call 111 or in serious cases call 999. 

How to get Mounjaro

Mounjaro is a prescription-only medication. You must meet set criteria to be prescribed Mounjaro by a registered healthcare professional. If you are interested in starting your weightloss journey and think you might meet the criteria for a tailored weight loss treatment, Pharmacy2U offer online consultations in which our GPs and pharmacists will assess your case and communicate with your NHS provider should you meet the requirements for a weight loss treatment such as Mounjaro.