Search "weight loss tablets" in Ireland and you will find a muddle of brand names, pharmacy shelves, prescription rules and very little plain explanation. Two of the names that come up most are orlistat (sold as Xenical and Alli) and Mysimba. They are very different medicines, licensed for slightly different people, and neither works the way the newer injections do. Here is what the official product information says.
Quick answer (checked 3 October 2026): orlistat blocks some of the fat you eat from being absorbed. Alli is the 60 mg version, sold in pharmacies without a prescription; Xenical is the 120 mg version, prescription-only. Mysimba is a different tablet that acts on appetite signals in the brain and is prescription-only. Prices vary by pharmacy, so check the current price with your pharmacist.
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The three names, and what each one is
The first source of confusion is that "orlistat" is a medicine name, not a brand. The same active ingredient is sold at two strengths, under two different sets of rules in Ireland:
- Alli (orlistat 60 mg) — authorised for adults with a BMI of 28 or above, used with a mildly reduced-calorie, lower-fat diet. In Ireland it is not subject to prescription and is supplied through pharmacies only.
- Xenical (orlistat 120 mg) — a prescription medicine, supplied through pharmacies only.
- Mysimba (naltrexone/bupropion) — a prescription medicine containing two different active ingredients, not orlistat at all.
All three are authorised across the EU by the European Medicines Agency. The Irish Health Products Regulatory Authority (HPRA) lists the supply status of each one on its public register, which is where the pharmacy-only and prescription details above come from.
How orlistat works, in plain English
When you eat a meal, enzymes in your gut called lipases break fat down into pieces small enough to absorb. Orlistat blocks those enzymes. The European Medicines Agency describes the result as about a quarter of the fat in a meal passing through undigested, in the case of the 60 mg Alli capsule.
The medicine itself is barely absorbed into the body; it does its work inside the gut. That is why the side effects are mostly digestive, and why the instructions are tied to meals. You take a capsule with water just before, during or up to an hour after each main meal, and you skip the dose if you skip the meal or the meal contains no fat.
How Mysimba works, in plain English
Mysimba combines naltrexone and bupropion in one slow-release tablet. The product information is honest that the exact mechanism is not fully understood. The two ingredients are thought to act on two parts of the brain: an area of the hypothalamus involved in appetite, and the "reward" system linked to cravings.
So orlistat changes what your gut absorbs, while Mysimba is aimed at appetite and food reward. Because bupropion and naltrexone are active in the brain, the list of people who cannot take Mysimba is considerably longer than for orlistat, as the next sections show.
Who each one is licensed for
| Medicine | Licensed for | Supply in Ireland |
|---|---|---|
| Alli 60 mg | Adults with BMI 28 or above, with a mildly reduced-calorie, lower-fat diet | Pharmacy only, no prescription |
| Xenical 120 mg | BMI 30 or above, or overweight (above 28) with associated risk factors | Prescription, pharmacy only |
| Mysimba | Adults with BMI 30 or above, or 27 to under 30 with a weight-related condition | Prescription, pharmacy only |
All three are meant to be used alongside diet and activity changes, not instead of them. Each has a built-in checkpoint too: Xenical should be stopped after 12 weeks if at least 5% of starting body weight has not been lost, and Mysimba after 16 weeks. Alli's product information says treatment should not exceed 6 months and to speak to a doctor or pharmacist if no weight is lost after 12 weeks.
One practical note on Mysimba: it is authorised in Ireland, but the HPRA register lists its marketing availability as unknown. That means a licence does not guarantee a pharmacy stocks it, so ask your pharmacist or prescriber before assuming you can get it.
Side effects, at the frequency the product information gives
The European product information ranks side effects by how often they occur: "very common" means more than 1 in 10 people. These are not the only effects, so read the leaflet that comes with the medicine.
- Alli (orlistat 60 mg), very common: oily spotting, wind with discharge, urgent need to open the bowels, fatty or oily stools, oily evacuation, flatulence and soft stools.
- Xenical (orlistat 120 mg), very common: the same digestive effects, plus headache, abdominal pain or discomfort and upper respiratory infections.
- Mysimba, very common: nausea, constipation, vomiting and headache. Common effects include dizziness, dry mouth, trouble sleeping and anxiety.
For orlistat, the digestive effects are linked to the fat in the meal. The Alli leaflet says they typically occur in the first few weeks, before people learn how much fat to limit. Orlistat can also reduce absorption of fat-soluble vitamins (A, D, E and K), so Xenical's product information suggests considering a multivitamin.
Mysimba carries extra cautions. Its product information describes reports of suicidal thoughts and behaviour in people taking bupropion, advises measuring blood pressure and pulse before and during treatment, and warns that serious reactions have been seen when it is combined with opioids.
Who should not take them
The contraindications listed in the product information are firm. For orlistat (both strengths), they include chronic malabsorption syndrome, cholestasis and a known allergy to the ingredients. Xenical is also contraindicated while breast-feeding. Alli is contraindicated in pregnancy and breast-feeding, and must not be combined with ciclosporin, warfarin or other oral anticoagulants. Orlistat can also interact with levothyroxine, so tell your pharmacist what else you take.
Mysimba has a longer list. It must not be used by people with uncontrolled high blood pressure, a seizure disorder or history of seizures, a history of bipolar disorder, bulimia or anorexia nervosa, or opioid dependence. It is also contraindicated with other bupropion or naltrexone products, MAOIs and in severe liver impairment or end-stage kidney failure. It should not be used in pregnancy.
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We have not published price bands here because pharmacy prices for Alli, Xenical and Mysimba vary from shop to shop and change over time, and a figure we could not confirm at source today would be misleading. The most reliable approach is to ask two or three pharmacies for the current price per pack and per month.
Alli is bought over the counter at full price. Xenical and Mysimba need a prescription; whether either is covered by a HSE scheme is a question for your prescriber or pharmacist rather than something to assume.
How they differ from GLP-1 injections
The newer weight-management injections belong to a different class. GLP-1 based medicines act on appetite hormone signalling and are given by injection. Orlistat works in the gut and Mysimba on brain pathways, and both are tablets. They are not the same kind of treatment, and the evidence behind each is different.
The injections are prescription-only medicines with their own licence criteria, side effects and cautions, and a doctor decides whether one is appropriate. We cover what the treatment involves in our complete Mounjaro Ireland guide. Whichever route you consider, the medically sensible order is the same: licence criteria first, then a clinician who reviews your history.
When to talk to a GP or pharmacist
Speak to a pharmacist before buying Alli if you take any regular medicines, especially ciclosporin, warfarin, levothyroxine, amiodarone, diabetes or blood pressure medication, or antiepileptics. Speak to a GP or pharmacist if you have not lost weight after 12 weeks on Alli, if you see rectal bleeding, or if you have kidney disease.
Speak to a doctor first about Xenical or Mysimba, and before any weight-loss medicine if you are pregnant, breast-feeding, planning a pregnancy, under 18, or living with a mental health condition, high blood pressure or seizures. A doctor can also tell you honestly if a tablet is not the right fit.
If you would rather have a doctor look at the whole picture than choose a tablet from a shelf, the starting point is a proper medical assessment.
Frequently asked questions
What is orlistat used for?
Orlistat is licensed for weight loss in adults, used with a mildly reduced-calorie, lower-fat diet. It blocks the digestion of some dietary fat in the gut rather than acting on appetite.
Is Alli the same as Xenical?
Both contain orlistat. Alli is the 60 mg capsule, available from pharmacies without a prescription for adults with a BMI of 28 or above. Xenical is the 120 mg capsule and needs a prescription.
Do I need a prescription for orlistat in Ireland?
Not for Alli 60 mg, which is pharmacy-only but not prescription-only. Xenical 120 mg requires a prescription.
Is Mysimba available in Ireland?
Mysimba is authorised in Ireland as a prescription medicine, but the HPRA register lists its marketing availability as unknown, so ask a pharmacist or prescriber whether it can be supplied.
What are the main side effects of orlistat?
Mostly digestive: oily spotting, urgent bowel movements, oily stools and flatulence are listed as very common, meaning more than 1 in 10 people. They are linked to the fat content of meals.
Are these the same as weight-loss injections?
No. Orlistat acts in the gut and Mysimba in the brain, and both are tablets. The injections are a separate class of prescription-only medicine with their own criteria.
Further reading
- Weight loss pills in Ireland — what is licensed and what is available now
- Every weight-loss medication licensed in Ireland — injections, tablets and pharmacy options compared
- Mounjaro in Ireland: the complete guide — how the treatment works and follow-up
Sources: European Medicines Agency product information (SmPC) for Xenical, Alli and Mysimba (sections 4.1, 4.3, 4.4, 4.6, 4.8, 5.1).
HPRA register entries for Xenical, Alli and Mysimba, checked 3 October 2026. This article is general information, not medical advice; ask a doctor or pharmacist about your own situation.
