Reviewed by Virginia Chachati MPharm
(2013, University College London)
GPhC Registration number: 2087654
Information last reviewed 07/04/21
Xenical is a prescription only medicine that helps adults lose weight and treats obesity. Xenical is a brand of generic medicine orlistat. When used in combination with a healthy diet and regular exercise, Xenical can greatly improve your chances of losing weight effectively and safely.
Xenical works in the stomach and small intestine by blocking lipase, an enzyme, from digesting fat. Around a third of the fat you eat will be removed from your body in your stools rather than being absorbed. While this will help you avoid gaining weight, it will not necessarily make you lose weight, so treatment with Xenical must be accompanied by a healthy diet and regular exercise to be effective.
Weight loss with Xenical usually starts within two weeks. If you have not lost at least 5 % of your body weight within three months of starting Xenical, it may not be the right treatment for you. Otherwise, you can continue to take Xenical for up to 12 months or longer, under the guidance of your doctor.
Xenical should start working within two weeks. You should lose at least 5 % of your body weight after using Xenical for three months. However, Xenical only works when you eat fat, so it is important to make sure your diet is balanced rather than cutting our fat altogether. Whilst taking Xenical, you will follow a low fat diet and exercise regularly. A doctor will be able to advise you on a suitable weight loss programme to help you lose weight effectively and safely.
Xenical is effective after two weeks and you should lose at least 5 % of your body weight after three months. Xenical is the only prescription weight-loss medicine that is safe and effective in the UK. However, the effectiveness of Xenical differs from patient to patient, and it only works when accompanied by a low fat diet and regular exercise programme.
Dose |
One tablet, taken 3 times per day with meals |
Type of Medicine |
Lipase inhibitor (fat-binder) |
Mechanism |
Prevents the body from absorbing fats from food by blocking lipase activity |
Available Size |
42, 84, 168 or 252 capsules |
Available Strengths |
120mg |
Active Ingredient |
Orlistat |
Price |
From 57p per tablet |
Side Effects |
Can include oily, fatty or liquid stools, oily discharge, low blood sugar levels, rectal pain, incontinence, irregularity of menstrual cycle |
The active ingredient in Xenical is orlistat (120 mg).
The inactive ingredients in Xenical are microcrystalline cellulose (E460), sodium starch glycolate (type A), povidone (E1201), sodium laurilsulfate, talc, gelatine, indigo carmine (E132), titanium dioxide (E171) and edible printing ink.
Always take Xenical as instructed by a doctor or pharmacist. Xenical should be taken in combination with a low-fat and calorie-controlled diet. Try to eat plenty of fruits and vegetables. Limit your fat intake to 30 % of your total daily calories. You should distribute your daily intake of fat, carbohydrate and protein evenly across your three daily meals. Swallow one capsule with water immediately before, during or within an hour of each meal. For best results, avoid eating fat-containing foods between meals, such as biscuits, chocolates and crisps.
If you miss a meal, or eat a meal that does not contain fat, you do not need to take a Xenical capsule. If you forget to take a capsule, try and remember to take it within an hour of your last meal. If an hour has already passed, just skip the dose and take your next one as planned with your next meal. Never take a double dose to make up for a missed one.
Always take Xenical as your doctor has prescribed. The usual dose is one Xenical 120 mg capsule taken with each of your three main meals per day.
After you complete your treatment with Xenical, you should stick to a healthy, balanced diet and exercise regularly to avoid putting weight back on. If you have not lost at least 5 % of your body fat within three months, your doctor may discontinue the treatment course with Xenical.
Usually, you can stop taking Xenical if you have not lost at least 5 % of your body weight after three months. If you feel you need to stop taking Xenical due to side effects then let your doctor know so you can discuss an alternative treatment plan.
You will need to follow a calorie-reduced low-fat diet plan and regular exercise programme before starting Xenical, during your treatment course and after your prescription has ended.
Xenical can cause side effects in some patients. If you feel unwell while taking Xenical, tell your doctor or pharmacist as soon as possible.
The following side effects can occur in more than 1 in every 10 patients:
Common side effects (affecting 1 to 10 in 100 patients) include:
The following side effects have been reported, although it is not known how often they occur:
Xenical is not absorbed by the body and works locally in the stomach and small intestine to block a third of the fat you eat from being digested. The best way to minimise side effects is to maintain a low-fat diet. Taking Xenical with a high-fat meal can lead to abdominal cramps with oily stools or diarrhoea, as your body will get rid of a third of the fat you are eating. Plan your meals to include wholegrains, fruits, vegetables and lean cuts of meat.
You should NOT take Xenical if:
Take extra care whilst taking Xenical if:
Before taking Xenical, let your doctor or pharmacist know if you are taking any other medicines, including those purchased over the counter at a pharmacy without a prescription. Remember that weight loss may lead to the dose of your other medicines being changed. Important medicines you should let them know about include:
Whilst taking Xenical, you should drink no more than the recommended number of alcohol units as stated on the NHS website. Xenical reduces how quickly alcohol is broken down by your body, so avoid drinking alcohol immediately after taking a Xenical capsule.
Xenical can disrupt menstruation because it affects how much fat your body can absorb. If your period is irregular, delayed, or stops altogether, it may be that your body is not absorbing enough fat and treatment with Xenical may need to be discontinued or your diet may need to be adjusted. Speak to your doctor for advice if you are worried that your menstrual cycle has changed whilst taking Xenical.
Xenical is the only prescription weight loss treatment that is proven to be effective and safe. Remember that Xenical only works if dietary fats are present in the body. You can use meal replacement products to help lower your overall calorie intake each day. You may want to discuss your weight loss goals with your doctor before using additional weight loss treatments.
Xenical is a brand name of the generic medicine orlistat. They work in the same way and the active ingredient in both is orlistat 120 mg. Orlistat is slightly cheaper to buy than Xenical.
Xenical (orlistat 120 mg) is the only prescription weight-loss medicine that is proven to be safe and effective. A lower dose of Xenical under the brand name Alli, which contains 60 mg orlistat, is available to buy over the counter under the supervision of a pharmacist. However, no weight-loss product will help you lose weight if you maintain a high-calorie diet. Try to lose weight by making sustainable long-term changes to your dietary and exercise habits.
Xenical is not an appetite suppressant. It blocks a third of the fat you eat from being absorbed by your body, to help maintain a calorie deficit, which will help you lose weight.
In order to lose weight effectively, you should exercise regularly while taking Xenical. A doctor can provide you with an effective weight loss programme that is right for you.
Xenical is only prescribed for the treatment of obesity where other weight-loss methods have previously failed. If you suspect that someone you know is using Xenical to lose weight because they have an eating disorder, you can let them know you are worried about them and suggest they talk to a healthcare professional. This can be difficult, as people suffering from eating disorders are often very secretive about it and may not want to accept help from others. The NHS website offers advice on how to help if someone you know has an eating disorder.
Xenical can be taken in preparation for weight-loss surgery if advised by a doctor. Surgery is often the last resort and should only be offered where other weight-loss methods have failed. Often, surgeons will not operate unless a patient is below a certain weight, so Xenical may be incorporated into a weight-loss programme prior to surgery.
Xenical should only be taken following surgery under the advice of a doctor. You are unlikely to need Xenical if you have a gastric band fitted, but it may be prescribed following liposuction to help you keep off the weight you have lost.
The amount of weight you can lose on Xenical depends on the diet and exercise programme you follow while taking it. Xenical should help you lose weight within two weeks and reduce your body weight by at least 5 % after three months.
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