Weight loss medicines

Weight loss medicines are medications that can be used to help you lose weight when lifestyle changes – such as healthy diet and exercise – have not been successful on their own.

Weight loss medicines must be used together with diet and exercise to help you lose weight and get healthy. So while they are not a quick-fix, they can help you achieve weight loss when other methods have failed.

There are several prescription and non-prescription medicines and products available for weight loss in Australia. Your doctor and pharmacist can discuss with you the risks and benefits of these medicines.

When can weight loss medicines be used?

Unfortunately, weight loss medicines are not the answer for everyone trying to lose weight. Weight loss medicines are generally only recommended for people who have had repeated, unsuccessful attempts at losing weight and are:

  • obese (body mass index – BMI – of 30kg/m2 or greater); or
  • overweight (BMI of 27-30kg/m2) and have additional weight-related health problems.

Calculate your body mass index with our BMI calculator.

Weight loss medicines may also be suitable for:

  • helping to kick-start weight loss;
  • maintaining weight loss; or
  • treating or preventing weight regain after weight loss.

It’s important to remember that making healthy food choices, reducing your intake of calories and increasing the amount of physical activity that you do must be a part of your weight loss plan. Taking weight loss medications won’t result in healthy weight loss without making other changes to your lifestyle.

Weight loss medicines that are available in Australia include orlistat, phentermine and liraglutide. These medicines have been shown to help achieve and maintain weight loss when used in combination with lifestyle change.


Orlistat (brand names Xenical and Prolistat) is a medicine that has been shown to be effective in assisting and maintaining weight loss. It is available from pharmacists without a prescription.

How does orlistat work?

Orlistat works by interfering with digestive enzymes that are needed to break down and absorb fats. It limits fat breakdown in the gut so that one-third less fat is absorbed. The undigested fat passes through the gut and is excreted in the faeces.

A low-fat diet is essential when taking orlistat.

Side effects of orlistat

If too much fat is eaten, the side effects of orlistat are an oily rectal leakage and oily, fatty bowel motions, often accompanied by increased urgency to empty the bowels. These adverse effects usually provide an incentive for people to keep the fat content of their diet low, which helps change eating habits.

When taken long term, there is a risk of becoming deficient in fat-soluble vitamins (vitamins A, D, E and K). Your doctor may recommend a vitamin supplement to prevent vitamin deficiencies.

Long-term use of orlistat may also increase your risk of developing kidney stones.


Phentermine (brand names Duromine or Metermine) is an appetite suppressant. This means that when taking phentermine you will feel less hungry. These medicines require very close monitoring so your doctor should reassess your condition frequently. It is generally recommended that phentermine be taken for 3 months or less, together with a reduced calorie diet.

Who can take phentermine?

Phentermine is only available on prescription.

Phentermine should not be used in people with uncontrolled high blood pressure, certain heart conditions, glaucoma, an overactive thyroid gland, a history of a certain psychiatric disorders, or a history of drug or alcohol abuse or dependency. This medicine is also not suitable for pregnant women.

Side effects of phentermine

Side effects of phentermine include dry mouth, headaches, insomnia, restlessness, nervousness, agitation, fast heartbeat, high blood pressure and, rarely, psychosis and hallucinations.


Liraglutide (brand name Saxenda) is a medicine that suppresses appetite (an appetite suppressant). This medicine also lowers blood glucose (sugar) levels. Liraglutide is given by a daily injection under the skin using a special pen injector device.

Liraglutide is only available on prescription. It is not recommended for people with some types of heart disease, kidney failure or liver disease. It is also not recommended in people who have had major depression and some other psychiatric disorders.

Liraglutide should not be taken during pregnancy or breast feeding.

Side effects of liraglutide

Common side effects of liraglutide include nausea, vomiting, diarrhoea and constipation. Liraglutide can also increase your risk of developing gallstones or gallbladder inflammation.

Liraglutide also increases your heart rate, which may cause palpitations (an awareness of your heart beating rapidly).

The risk of pancreatitis (inflammation of the pancreas) may also be increased in people taking liraglutide.

Weight loss medicines that are no longer available


Sibutramine, brand named Reductil, was withdrawn from use in Australia in October 2010 following results of a major study which showed a higher rate of cardiovascular events (e.g. heart attack or stroke) in obese and overweight patients taking sibutramine, than in those managing their weight through exercise and diet alone.

Sibutramine is a serotonin and noradrenaline reuptake inhibitor, which works by affecting brain chemistry.


Fenfluramine was previously used as a weight loss medicine, both on its own and in combination with phentermine. The combination medication, known as fen-phen, was especially popular in the United States. Medicines containing fenfluramine were withdrawn from the market in 1997 because of concerns that they caused heart valve damage.

Diethylpropion hydrochloride

Diethylpropion hydrochloride, brand named Tenuate or Tenuate Dospan, is another prescription medicine that was previously used in conjunction with calorie restriction, on a short-term basis only, in obese people. It has been withdrawn from the market.

Side effects included an irregular heartbeat, high blood pressure, dry mouth, nausea, abdominal discomfort, seizures and nervousness, and there were some reports of people becoming psychologically dependent on this medicine.

Herbal and alternative treatments

There are many non-prescription medicines and herbal remedies available that reportedly help with weight loss. Ask your doctor before trying these treatments, because most have not been tested in the same way as prescription medications, and their safety and effectiveness are often unproven.

Remember, weight loss medicines only work when they are used in combination with lifestyle modifications, such as increased exercise and decreased food intake.

Author: myDr


1. Overweight and obesity (published November 2012). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2016 Jul. http://online.tg.org.au/complete/ (accessed Nov 2016).
2. Australian Diabetes Society, the Australian and New Zealand Obesity Society (ANZOS) and the Obesity Surgery Society of Australian and New Zealand. Australian obesity management algorithm (Oct 2016). https://www.anzos.com/australian-obesity-management-algorithm (accessed Nov 2016).


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