Xenical, Alli and Orlistat are essentially three different names for the same drug. Orlistat is the active ingredient in each of these medications and is also the generic name for the drug. The generic name is the name given to the medication based on its active ingredient. Xenical and Alli are both brand names of orlistat. Xenical contains 120mg of orlistat and Alli contains 60mg of orlistat, so Xenical contains twice as much of the active drug as Alli. For this reason, Xenical is only available on prescription, but Alli can be purchased over the counter.
How do these medications work?
When you eat a meal, the fat is usually digested by an enzyme called lipase. If you eat more fat than you need, it is stored by the body causing you to put on weight.
Orlistat works by blocking the lipase. This reduces the amount of fat you digest. So the fat passes out in your stools instead.
How long do they take to work?
Orlistat usually starts to interfere with your fat digestion within 1-2 days. This should help to stop you putting on weight. However, weight loss takes much longer. You may not achieve any noticeable weight loss until you have been taking orlistat for several weeks.
It is important to be aware that orlistat works best when combined with a healthy low-calorie diet and exercise. Usually, we hope that you would be able to lose about 5% of your initial body weight after taking orlistat for 3 months. You may experience more or less weight loss than this. If you do not experience this much weight loss, orlistat may not be the most suitable treatment option for you.
How effective are they?
The effectiveness of orlistat can vary from person to person and also depends upon what dose you are taking. If you are taking a 120mg dose of orlistat, such as Xenical, the amount of fat you digest should be reduced by ⅓. If you are taking a 60mg dose, such as Alli, the amount of fat digestion should be reduced by ¼.
What are the side effects?
As with all medications, orlistat can cause some side effects. You are more likely to experience side effects at higher doses, meaning you may experience less with Alli or 60mg generic orlistat. The most common side effects you will experience are gastrointestinal – your body is no longer processing as much fat from your food, meaning you may experience upset stomachs, diarrhoea and oily stools. In some cases, patients may experience oily discharge after high-fat meals. Please read the Xenical and Alli Patient Information Leaflets for a full list of possible side effects of each dose.
How safe are they?
Xenical, Alli and generic orlistat are all considered safe to help lose excess weight. They should not be used by people who are a healthy weight.
However, there are some situations in which orlistat (including Xenical or Alli) may not be suitable for you. Orlistat must not be taken by anyone suffering from cholestasis or chronic malabsorption syndrome. You should not take orlistat during pregnancy or whilst breastfeeding as this could have harmful effects on your child.
Some medical conditions can increase the risk of orlistat. Therefore, you may need additional monitoring if you have chronic kidney disease or if you are taking certain vitamin supplements.
Orlistat can also interact with some medications including epilepsy and HIV treatments. For this reason, you should always inform the doctor or pharmacist of any medications or pre-existing health conditions before taking orlistat in any form.
Xenical vs Alli vs orlistat: which are available over the counter?
You can buy orlistat, Alli and Xenical in the UK. Orlistat is available both over the counter and on prescription depending upon the dose. Treatments containing 60mg of orlistat, such as Alli and Orlos, tend to be available over the counter, whereas 120mg treatments like Xenical are prescription only. Generic orlistat is not available over the counter in the UK.
Can you take Xenical and Alli together?
No, Xenical and Alli must not be taken together. This is because they both contain the active ingredient, orlistat. Taking Xenical and Alli together could cause an overdose of orlistat which could be dangerous. Never use two medications containing orlistat together unless instructed to do so by a medical professional.