Mounjaro

Mounjaro is a prescription-only, once-weekly injection containing tirzepatide. It belongs to a class of medicines that act on two hormone receptors, GIP and GLP-1, which play a role in regulating appetite and blood sugar levels.

Mounjaro is licensed in the UK for weight management in eligible adults and is used alongside a reduced-calorie diet and increased physical activity. It is supplied as a pre-filled KwikPen containing four weekly doses.

Mounjaro contains tirzepatide, which mimics the action of two naturally occurring hormones, GIP and GLP-1. These hormones help regulate appetite and how the body responds to food.

By acting on both hormone pathways, Mounjaro helps reduce hunger, increase feelings of fullness and slow the rate at which food leaves the stomach. This can help you feel satisfied with smaller portions and reduce your overall calorie intake.

When combined with a balanced, reduced-calorie diet and regular physical activity, these effects can support gradual, sustained weight loss.

Mounjaro is injected once a week, on the same day each week, using a pre-filled KwikPen. It can be taken at any time of day, with or without food.

The injection is given just under the skin of your stomach, thigh or upper arm. You should rotate injection sites each week to help prevent irritation.

Treatment starts at 2.5 mg once weekly for four weeks, before increasing to 5 mg. Your prescriber may recommend further dose increases depending on your progress and how well you tolerate treatment.

If you miss a dose, take it as soon as possible within four days (96 hours). If more than four days have passed, skip the missed dose and take your next injection on your usual scheduled day. Never take two doses within three days (72 hours) of each other.

The SURMOUNT-1 clinical trial found that adults taking tirzepatide 15 mg once weekly achieved an average 20.9% reduction in body weight after 72 weeks, compared with 3.1% in the placebo group. Participants also received guidance on diet and physical activity.

Results varied depending on the dose, and individual weight loss is not guaranteed. Your progress will depend on several factors, including your response to treatment and lifestyle habits.

Like all medicines, Mounjaro can cause side effects, although not everyone experiences them. These are often more noticeable when starting treatment or increasing your dose and may improve as your body adjusts.

Common side effects include:

• Nausea, vomiting, diarrhoea and constipation.
• Stomach pain, bloating, indigestion and burping.
• Reduced appetite and feeling unusually tired.

How can I manage side effects?

Eating smaller meals, avoiding rich or fatty foods and drinking plenty of fluids may help. If side effects become troublesome or do not improve, contact your prescriber for advice before increasing your dose.

When should I seek medical help?

Stop taking Mounjaro and seek urgent medical attention if you experience severe, persistent stomach pain, particularly if it spreads to your back, as this could indicate pancreatitis.

Seek emergency help if you develop difficulty breathing or swelling of your face, lips or throat, which may indicate a serious allergic reaction.

Persistent vomiting or diarrhoea can cause dehydration. Seek medical advice promptly if you are unable to keep fluids down.

For further information, refer to the Patient Information Leaflet supplied with your Mounjaro pen.

Mounjaro may be prescribed for weight management in adults who meet either of the following criteria:

• BMI of 30 or above, indicating obesity.
• BMI of 27 or above, with at least one weight-related health condition, such as high blood pressure, type 2 diabetes or high cholesterol.

Lower BMI thresholds may be considered for people from certain ethnic backgrounds, in line with relevant clinical guidance.

Before prescribing Mounjaro, your prescriber will review your medical history, current medications and overall health to determine whether treatment is appropriate for you.

Mounjaro is not suitable if you are allergic to tirzepatide or any of its ingredients. It should not be used during pregnancy.

Mounjaro should also not be used if you:

• Are planning a pregnancy.
• Are taking another tirzepatide or GLP-1 medicine, unless switching under medical supervision.

Tell your prescriber if you:

• Have a history of pancreatitis.
• Have severe digestive problems, including delayed stomach emptying.
• Have diabetic eye disease or kidney problems.
• Take insulin or other diabetes medicines.

Mounjaro should be stopped at least one month before a planned pregnancy.

Contraception: Mounjaro may reduce the effectiveness of oral contraceptive pills. Use additional barrier contraception or switch to a non-oral method for four weeks after starting treatment and after each dose increase.

Mounjaro can be used as a long-term treatment for weight management, with no fixed maximum duration. How long you continue will depend on your progress, how well you tolerate the medicine and whether it remains suitable for you.

Your prescriber will regularly review your weight, treatment response and any side effects to ensure Mounjaro continues to meet your needs.

Stopping treatment may lead to weight regain, so maintaining a balanced diet, regular physical activity and sustainable lifestyle habits is important for keeping weight off in the long term.