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Slimming Pills


Slimming pills (or diet pills) and weight loss products can be sold as over-the-counter (OTC) medicines or available as prescription medicines. Most of the OTC diet pills or weight loss products make claims that they are effective but their claims are not backed-up by scientific evidence. In fact, these weight loss products need to be taken in conjunction with other measures such as exercise and diet. Some of these products are based on herbs.

There are only three types of prescription medicines that can help obese or overweight patients to loose weight.

Over The Counter Products (OTC)

Slimming products that can be bought without a prescription often come with recommendations that you follow a calorie-controlled diet and take more exercise. Most of these pills or products do not have enough information about their ingredients and how they help you lose weight. They can also be very expensive.

When Taking OTC Diet Pills/Weight Loss Products

  • Check that the product you are going to buy is registered with the regulatory authority (check www.bpfk.gov.my for this information).
  • Some of the products (including herbal products) may also cause adverse effects. Make sure you do not have other medical conditions if you want to try these products.
  • Read the label carefully and do not take more than the listed dose.
  • These products are licensed as either OTC, traditional or cosmetics product; therefore they are not allowed to make certain claims such as “stops fat from being absorbed” or “speeds up metabolism”. If you find these claims being made on the packaging or product insert, report it to the regulating authority.
  • Ephedra is a herb that was commonly incorporated in slimming products but has now been banned because of its adverse effects. It is a myth that herbal slimming products are safe. Beware of anything that you take even if recommended by your friends as being safe and effective.
  • Avoid slimming products which:
    • Promote rapid weight loss and promise quick results
    • Suggest that you do not need to change your diet or exercise.
    • Fail to recommend a dietary advice; and worse still encourage you to eat anything.

Prescription Medicines

Prescription medicines are licensed as treatment of obesity. Two types of licensed medicines are:

What is it for?

Orlistat is used in combination with diet to help you loose weight and maintain weight after weight loss. It is also used in patients with a certain weight who may also have other medical conditions such as diabetes and hypertension.

How does it work?

Orlistat is a lipase inhibitors, which works in the intestines by blocking some of the fat you eat from being digested and absorbed. This undigested fat is then removed in your bowel movements.

“How to use this medicine?

Orlistat comes as a capsule. It is usually taken three times a day with each main meal that contains fat. Each time you take orlistat, your meal should contain no more than about 30% of calories from fat. Take orlistat during or up to 1 hour after a meal. If a meal is missed or does not have fat, you may skip your dose.

Special dietary instructions

Orlistat blocks your body’s uptake of some fat-soluble vitamins and beta carotene. Therefore, when you use orlistat you should take a daily multivitamin supplement that contains vitamins A, E, K, and beta-carotene. Take the vitamin once a day, 2 hours before or 2 hours after taking orlistat, or take the vitamin at bedtime.


The most common side effect of orlistat is changes in bowel movement (BM) habits which generally occurs during the first weeks of treatment. However, it may continue throughout use of orlistat.

Ask your doctor or pharmacist what the symptoms of BM changes are. Refer to your doctor if any of the symptoms are serious or do not go away.

What is it for?

Sibutramine is used in combination with a reduced calorie diet and exercise to help people who are overweight lose weight and maintain their weight loss.

How does it work?

Sibutramine is in a class of medications called appetite suppressants. It works by acting on appetite control centers in the brain to decrease appetite.

How to use this medicine?

It is in the form of capsule, usually taken with or without food once a day. To help you remember to take sibutramine, take it around the same time every day. Sibutramine can be habit forming. Do not take more or less of it or take it more often or for a longer time than prescribed by your doctor.

Special dietary instructions

Follow the diet and exercise program your doctor has given you.


Sibutramine may cause side effects such as headache, constipation, heartburn, dry mouth, weakness, back pain, nervousness, change in apetite, flushing, flu-like symptoms and painful menstrual periods.

Tell your doctor if any of these symptoms are severe or do not go away.

And, centrally acting appetite suppressants, namely

What is it for?

Phentermine is used in combination with diet and exercise to help people who are overweight lose weight.

How does it work?

It is in a class of medications called appetite suppressants which acts on appetite control centers in the brain to decrease appetite.

How to use this medicine?

Phentermine comes in tablets and extended-release capsules. It is usually taken as a single daily dose in the morning or three times a day 30 minutes before meals.

The length of treatment depends on the individuals’s response to the medication, although most people take the drug for 3-6 weeks. Phentermine can be habit-forming. Do not take a larger dose, take it more often, or for a longer period than your doctor tells you to.
To prevent side effects, phentermine should be taken with meals. If you are taking an extended-release (long-acting) product, do not chew or crush the tablet.

Special dietary instructions

Follow the diet and exercise program your doctor has given you. It is effective when used in combination with a diet programme.


Phentermine may cause side effects such as dry mouth, unpleasant taste, diarrhoea, constipation and vomiting. Tell your doctor if any of these symptoms are severe or do not go away.

If you experience more severe side effects such as increased blood pressure, heart palpitations, restlessness, dizziness, tremor, sleep disturbance, shortness of breath or chest pain, call your doctor immediately.

  • Anti-obesity medicines (AOM) that act on the gastrointestinal tract (GIT), namely:
    • Orlistat
  • And, centrally acting appetite suppressants, namely
    • Sibutramine
    • Phentermine

Obesity is associated with many medical and health problems. These include diabetes mellitus, osteoarthritis and cardiovascular diseases. The main treatment for obesity is a suitable diet, which should be explained carefully, with full support and encouragement; and increase in physical activity.

Antiobesity medicines are being considered only for individuals with a body mass index (BMI) of 30 kg/m2 or more. A BMI of 27 kg/m2 or more is appropriate if an individual also has other risk factors such as diabetes, hypertension or heart disease; which depends on consultation with a doctor.

Medicines should never be used alone; and monitoring of the individual’s weight on a regular basis should be conducted. Treatment with medicine should be discontinued if weight loss is less than 5% after the first 12 weeks or if the individual gain weight at any time, whilst on treatment. Combination therapy is contraindicated.

General Information

Take your medicines exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Follow the directions on your medication label carefully, and ask your doctor or pharmacist to explain any part you do not understand.

Storage Conditions

Keep your medicine in its original container tightly closed. Store at room temperature and keep away from children, excess healt or moisture. Throw away medicines which have expired or are spoiled. Ask your pharmacist the correct way to dispose your medicine.


Last reviewed : 25 May 2007
Writer : Dr. Nour Hanah Othman
Accreditor : Yam Chiew Fong