Mounjaro

About Mounjaro

Mounjaro is a prescription-only weight management injection made by Eli Lilly. Its active ingredient, tirzepatide, is what is known as a dual agonist, it activates two different gut hormone receptors rather than one, which is what sets it apart from every other treatment in the category.

It is supplied as a KwikPen, a pre-filled multi-dose pen that delivers four weekly doses. The pen has a hidden needle and a simple dial, so there is no drawing up or measuring involved.

How much weight can you expect to lose?

In the SURMOUNT-1 trial, adults without diabetes taking the highest dose alongside lifestyle changes lost an average of around 21% of their starting body weight over 72 weeks. On the lowest maintenance dose the average was around 15%.

Individual results vary considerably. Weight loss is fastest in the first six months and tends to plateau as you approach your body's new set point.

Who is Mounjaro for?

Mounjaro may be prescribed for weight management if you are an adult with a BMI of 30 or above, or a BMI of 27 or above alongside a weight-related condition such as high blood pressure, type 2 diabetes, obstructive sleep apnoea or raised cholesterol. Lower BMI thresholds apply if you are of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background.

How Mounjaro works

Tirzepatide mimics two hormones your gut releases after eating: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Every other GLP-1 medicine on the market targets only the second of those.

The GLP-1 effect

Activating the GLP-1 receptor slows how quickly your stomach empties, prompts insulin release when glucose is high, and acts directly on the appetite centres in the hypothalamus to reduce hunger.

The added GIP effect

GIP receptor activation appears to improve how efficiently the body handles fat and to enhance the appetite-suppressing signal from GLP-1. The working theory is that the two pathways together produce a stronger effect than either alone, which matches what the trial data shows.

What it feels like day to day

Most people notice that they feel full much earlier in a meal, that they think about food far less between meals, and that highly palatable foods lose some of their pull. The effect builds over the first few weeks and steps up again with each dose increase.

How to use Mounjaro

When to inject

Inject once a week, on the same day each week. You can inject at any time of day, with or without food. If you need to change your injection day, make sure there are at least three days between doses.

Where to inject

Into the fatty tissue just under the skin of your stomach (avoiding a 5cm circle around the navel), your thigh, or the back of your upper arm. Rotate the site each week to avoid irritation.

Step by step

• Take the pen out of the fridge, injecting at room temperature is more comfortable
• Check the liquid is clear and colourless
• Clean the skin and let it dry
• Unlock the pen, press the base flat against the skin, hold the injection button
• Keep holding until the second click and the grey plunger is visible, around 10 seconds
• Lift away and dispose of the pen in a sharps bin when all four doses are used

Dose schedule

You start on 2.5mg for four weeks. This starting dose is for tolerance only. It is not expected to produce meaningful weight loss. You then step up to 5mg, and continue increasing in 2.5mg steps every four weeks until you reach a dose that works for you, up to a maximum of 15mg.

Missed dose

Inject as soon as you remember, as long as it is within four days of the missed dose. If more than four days have passed, skip it and take the next one at the usual time. Never double up.

Side effects

Most side effects are digestive, appear during the first few weeks or after a dose increase, and settle as your body adjusts.

Very common (more than 1 in 10 people)

• Nausea
• Diarrhoea
• Constipation
• Vomiting

Common (up to 1 in 10 people)

• Abdominal pain, bloating or indigestion
• Reduced appetite and burping
• Tiredness
• Injection site reactions
• Hair loss
• Low blood sugar, particularly if you also take insulin or a sulfonylurea

Seek medical advice urgently

• Severe, persistent abdominal pain that may radiate to your back, with or without vomiting, this can indicate pancreatitis
• Signs of an allergic reaction such as swelling of the face, lips or throat, or difficulty breathing
• Severe pain in the upper right abdomen, fever or yellowing of the skin or eyes, possible gallbladder problems
• Symptoms of dehydration from persistent vomiting or diarrhoea

Reducing nausea

Eat smaller portions, stop as soon as you feel full, avoid fatty and fried food, stay upright after eating and sip fluids steadily through the day.

Ingredients

Active ingredient: tirzepatide.

Other ingredients: sodium phosphate dibasic heptahydrate, sodium chloride, water for injections, and hydrochloric acid or sodium hydroxide for pH adjustment.

Each pre-filled KwikPen delivers four weekly doses. Available strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg per dose.

Important safety information

Do not use Mounjaro if you:

• Are pregnant, trying to conceive or breastfeeding
• Have a personal or family history of medullary thyroid carcinoma, or multiple endocrine neoplasia syndrome type 2
• Have had pancreatitis
• Have type 1 diabetes or diabetic ketoacidosis
• Are allergic to tirzepatide or any other ingredient

Speak to your prescriber first if you have kidney or liver disease, gallstones, diabetic retinopathy, a history of eating disorders, or take insulin or a sulfonylurea.

Contraception: Mounjaro can reduce the effectiveness of oral contraceptives, particularly around dose increases. Use an additional barrier method for four weeks after starting and for four weeks after each dose increase, or switch to a non-oral method.

Mounjaro is a prescription-only medicine and must be prescribed following a consultation with a qualified prescriber. Always read the patient information leaflet supplied with your medicine.