Common questions about weight loss medicines

Weight loss medicines are best used as part of an overall weight-loss plan that includes a calorie controlled healthy diet and regular exercise.

Weight loss medicines available in New Zealand are orlistat (Xenical), phentermine (Duromine), liraglutide (Saxenda) and naltrexone/buproprion (Contrave).

On this page, you can find the following information:

What are weight loss medicines?

Weight loss medicines are used to help you lose weight when lifestyle changes, such as healthy diet and exercise, have not been successful on their own. If you are overweight or obese, weight loss can improve your health and help treat or prevent health problems related to being overweight or obese.

A routine of healthy eating and regular exercise can provide lasting weight loss. However, for some people this is not enough and weight loss medicines may help. Weight loss medicines are not a ‘quick fix’, but a long-term option for managing obesity when combined with healthy eating and exercise. 

The weight loss medicines available in New Zealand are:

  • naltrexone/buproprion (Contrave)
  • liraglutide (Saxenda)
  • orlistat (Xenical)
  • phentermine (Duromine).

When are weight loss medicines considered for use?

The use of weight loss medicines depends on your body mass index (BMI). BMI is calculated using your height and weight. Learn more about BMI.

  • A weight loss medicine may be considered for people with a BMI of 30 or greater if they have tried lifestyle modifications for at least 6 months without successful weight loss.
  • Saxenda, Contrave and Duromine may be used for people with a BMI ≥ 27 if they have at least 1 weight related health problem, eg, high glucose levels, high blood pressure, high cholesterol or obstructive sleep apnoea.

Are there other medicines that can be used for weight loss?

If you have diabetes, then the best glucose lowering therapies to help with weight loss are metformin, empagliflozin and dulaglutide. Talk to your health care professional about whether these medications are appropriate for you.

Are all weight loss medicines the same?

No, all weight loss medicines are not the same. Each works in different ways, has different side effects and the cost may differ too. Your healthcare provider will discuss the various options with you.

Note: These medicines are not subsidised, which means you'll have to pay for them. They vary in price, costing between $100 and $500 per month. Ask your healthcare provider how much they will cost before you start your course. The prices mentioned below give you an idea of the estimated cost as at September 2022.

Weight loss medicines available in New Zealand


  • Xenical prevents some of the fat you eat from being absorbed by your body.
  • It's available as a capsule.
  • Xenical can be purchased from pharmacies without a prescription. A pharmacist needs to make sure it's the best option for you and needs to record your name and address.
  • Estimated cost: $150/month.  
  • Read more about Xenical.

Phentermine (also called Duromine) 

  • Phentermine is a stimulant that acts on areas of your brain involved with appetite.
  • It can help weight loss by decreasing your hunger, making you feel full for longer and increasing the amount of energy used by your body.
  • It's available as capsules.
  • Phentermine is available on prescription only.
  • Estimated cost: $100/month.  
  • Read more about phentermine.


  • Saxenda suppresses your appetite by increasing feelings of fullness and reducing feelings of hunger.
  • It comes as an injection given under the skin in your tummy area, upper arm or thigh.
  • It's only available on prescription.
  • Estimated cost: $500/month.  
  • Read more about Saxenda.


  • Contrave contains 2 medicines in each tablet – naltrexone and bupropion.
  • It works on areas of your brain involved in appetite and food craving and increases the amount of energy used by your body.
  • If you haven't managed to lose at least 5% of your initial body weight after 16 weeks, treatment should be discontinued.
  • It's only available on prescription.
  • Estimated cost: $250/month.  
  • Read more about Contrave.

Why is it important to make lifestyle changes when you use weight loss medicines?

The effects of weight-loss medicines are not permanent. When they stop taking them, most people will regain weight over time. However, adopting healthy lifestyle habits may help limit weight gain.

Calorie-controlled eating

  • It's important to adopt a healthy eating plan, eg, a balanced and nutritious diet that meets your daily energy requirements.
  • It's also important that you can maintain the diet long-term, rather than a choosing a fad, or quick fix diet.

Regular exercise

  • At least 2.5 hours of moderate intensity physical activity per week should be included in all weight loss plans.
  • Exercise also leads to increased muscle mass and fitness, and improved heart health and mental health.
  • Perform muscle strengthening activities 2 days of each week.
  • Some physical activity is better than none – increasing physical activity of any kind is beneficial.

Image: Canva

Are weight loss medicines a long-term treatment?

Different people respond differently to weight loss medicines and your healthcare provider can help you decide whether using weight-loss treatment long-term is suitable for you.

  • Once you have started treatment with a weight loss medicine, your healthcare provider will monitor you on a regular basis for side effects and your response to treatment.
  • Usually, people who lose weight after 12–16 weeks of treatment continue to lose weight at 1 year and beyond.
  • For people who are overweight or obese, a lasting weight loss of 5–10% can have important health benefits, eg, lowering blood pressure, blood glucose and triglyceride levels. If you are not managing to lose enough weight (eg, weight loss <5% at 3–4 months), the medication should be stopped, as the long-term benefits are likely to be outweighed by the risks and costs.

Are there medicines that should NOT be used for weight loss?

Yes, there are medicines that shouldn't be used for weight loss. These include:

  • Laxatives: Laxatives should not be used for weight loss. Any weight lost by using laxatives is short term, due to fluid or water loss. This is harmful as it can lead to serious problems such as dehydration and salt (electrolyte) disturbances, and in some cases dependence.
  • Thyroid hormones: Thyroid hormones such as Eltroxin are not appropriate for losing weight unless the weight gain was caused by an underactive thyroid (hypothyroidism). 
  • The use of diuretics, chorionic gonadotrophin, or amphetamines is not appropriate for weight reduction.


  1. Obesity and weight-loss management Research Review, NZ, 2020
  2. Weight loss – the options and the evidence BPAC, NZ, 2019
  3. Clinical guidelines for weight management of New Zealand adults Ministry of Health, NZ, 2017
  4. Contrave Medsafe, NZ
Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr Ryan Paul, Endocrinologist, Hamilton and Angela Lambie, Pharmacist, Auckland Last reviewed: 14 Sep 2022