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Xenical: what you should know

Xenical: what you should know

What is Xenical (Orlistat)?

Xenical capsules contain the active ingredient Orlistat, which is a type of medicine called a lipase inhibitor. It is used to aid weight loss in people who are obese.

How does Xenical (Orlistat) work?

Xenical is taken at meal times and works in your digestive system to prevent about one third of the fat in the food you eat from being digested. Xenical attaches to the enzymes in your digestive system (lipases) and blocks them from breaking down some of the fat you have eaten during your meal. This undigested fat is not absorbed into your body and is passed out with your faeces (stools).

This will help you avoid gaining weight, but will not necessarily cause you to lose weight. Therefore, it's still important to stick to your recommended diet and exercise plan.

Is Xenical an alternative to dieting?

No. Xenical will only work alongside a low calorie, low fat healthy diet combined with regular exercise. You must limit the calories you eat which come from fat to under 30% of your diet and distribute your daily intake of fat, carbohydrate and protein over three main meals. Find out what you should be eating when taking Xenical

Who can use Xenical?

Xenical is prescribed to aid weight loss in overweight people who have a body mass index (BMI) of 30kg/m² or more. It can also be prescribed to overweight people who have a BMI of 28kg/m² or more, if they also have additional risk factors for obesity-related diseases.

Xenical is NOT safe to use if you have certain medical conditions or are taking certain medications and therefore you must check with your doctor first to ensure it is safe to use and ensure you complete any online assessment honestly. If you are pregnant or breast feeding it is not safe to take Xenical.

How do you take Xenical?

  • One capsule should be taken immediately before, during, or up to one hour after each of the three main meals per day. If a meal is missed, or contains no fat, you should leave out the dose. This is because the medicine will have no effect if no fat has been consumed.
  • Each capsule should be swallowed whole with a glass of water.
  • Do not take more than one capsule with each meal, or more than three capsules per day. Higher doses have NOT been shown to be more effective and only put you at an increased risk of side effects.

Full instructions are contained in the patient information leaflet that comes with the medication.

How effective is Xenical?

Treatment with Xenical should only continue beyond three months if you have lost 5% of your body weight. It usually starts to affect how you digest fat within one to two days. If Xenical has not worked after three months, it is unlikely to be an effective treatment for you.

Xenical will not work if you do not combine it with a weight reducing diet and regular exercise.

Are there any side effects with Xenical?

Like all medicines, Xenical can cause side effects, although not everybody gets them. Side effects are more likely after eating meals containing high levels of fat.

Common side effects of Xenical include

  • Fatty or oily stools
  • Needing the toilet urgently
  • Passing stools more frequently
  • Oily discharge from your rectum (you may have oily spots on your underwear)
  • Flatulence (wind)

These side effects are much less likely to occur if you stick to a low-fat diet. If you get any side effects please speak to your doctor.

Xenical and vitamins

Xenical may reduce your body's ability to absorb Vitamins D, A, E and K from your food so you need to make sure you get enough of these from your diet and ensure you have a diet rich in fruit and vegetables, otherwise please see your doctor who may advise you to take a multivitamin supplement. (If a multivitamin supplement is recommended, it should be taken at least two hours after taking the Xenical).

Xenical and contraception

Women taking the oral contraceptive pill are advised to use an additional method of contraception, such as a condom, if they experience diarrhoea while taking Xenical. This is because the contraceptive pill may not be absorbed by your body if you have diarrhoea, so it may not be effective.

Please read the patient information leaflet that comes with the medication for a full list of side effects and warnings.

You can take an assessment online and if it is safe and appropriate our doctors will send a paper prescription to you in the post.

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Authors and editors

Reviewed and updated by: Our clinical team Date reviewed: 21-01-2023