Orlistat vs Ozempic in Australia

No randomised trial has compared orlistat with semaglutide at any dose; a Europe PMC search run on 6 October 2026 found none. The network meta-analyses that rank weight-loss drugs pool semaglutide across doses in their headline estimates; the BMJ 2026 analysis reports that its dose subgroup analyses found no credible differences, and none of them gives a headline estimate for Ozempic's 0.5 mg to 2 mg.

Orlistat. The largest trial is XENDOS: 3,305 adults in Sweden with a BMI of 30 or more, randomised to orlistat 120 mg or placebo three times a day with lifestyle changes for four years. Average loss at one year was 10.6 kg on orlistat and 6.2 kg on placebo; by year four, 5.8 kg against 3.0 kg. Type 2 diabetes developed in 6.2% against 9.0%, a difference confined to the 21% who started with impaired glucose tolerance. Only 52% of the orlistat group and 34% of the placebo group completed the four years. The 2007 Cochrane update pooled 16 orlistat trials (10,631 participants, one to four years): 2.9 kg (95% confidence interval 2.5 to 3.2 kg), or 2.9% of body weight, more than placebo; 54% lost at least 5% against 33%; dropout averaged 30 to 40%.

Ozempic. The Australian Product Information reports weight as a secondary outcome of the SUSTAIN diabetes trials. SUSTAIN 1 (388 adults with type 2 diabetes on no other diabetes medicine, 30 weeks): 3.7 kg at 0.5 mg, 4.5 kg at 1 mg, 1.0 kg on placebo. SUSTAIN 2 (1,231 adults, 56 weeks): 4.3 kg, 6.1 kg and 1.9 kg on sitagliptin. SUSTAIN FORTE (961 adults, 40 weeks): 6.9 kg at 2 mg against 6.0 kg at 1 mg. The one weight-management trial at an Ozempic dose is STEP 2: 1,210 adults with type 2 diabetes and a BMI of 27 or more, randomised to semaglutide 2.4 mg, 1.0 mg or placebo for 68 weeks. The abstract reports 9.6% loss at 2.4 mg against 3.4% on placebo; the 1.0 mg arm's 7.0% comes from Novo Nordisk's trial announcement, not the abstract.

Orlistat works in the gut and its side effects follow the unabsorbed fat. Semaglutide acts on appetite and stomach emptying; its side effects are nausea, vomiting, diarrhoea and constipation. No Xenical-branded document is on Medsinfo; the Australian orlistat document is for Orlistat Viatris, a generic that reports the Xenical trial data.

Orlistat. Oily spotting, flatus with discharge, faecal urgency, fatty or oily stool, liquid stools, increased defecation and faecal incontinence are listed as common or very common. Incidence rises with the fat content of the diet; the recommended limit is 30% of calories from fat, about 67 g a day. Events occurred mostly within the first three months and most people had one episode. In the first year of controlled trials 8.8% stopped because of adverse events against 4.9% on placebo. The Australian document gives categories, not percentages; the United States label, from the same seven trials, reports first-year oily spotting in 26.6% against 1.3% on placebo, faecal urgency 22.1% against 6.7% and faecal incontinence 7.7% against 0.9%. Vitamins D and E and beta-carotene fell more than on placebo, which is why a multivitamin is recommended. Rare post-marketing reports include severe liver injury, some fatal or requiring transplant, for which the document says no causal relationship has been established, and oxalate nephropathy that may lead to kidney failure.

Ozempic. In the pooled phase 3a trials nausea affected 17.0% on 0.5 mg and 19.9% on 1 mg against 6.3% on comparators; diarrhoea 12.2% and 13.3% against 5.7%; vomiting 6.4% and 8.4% against 3.3%. Any adverse event led 6.1% and 8.7% to stop against 1.5% on placebo. At 2 mg, gastrointestinal disorders affected 34.0% against 30.8% at 1 mg over 40 weeks. Acute pancreatitis occurred in 0.3% against 0.2%; the document says to stop if pancreatitis is suspected and not restart if confirmed. Hypoglycaemia is very common when semaglutide is used with insulin or a sulfonylurea. Diabetic retinopathy complications occurred in 3.0% against 1.8% on placebo in SUSTAIN 6, mostly in insulin-treated people with existing retinopathy. Warnings also cover dehydration and kidney injury after severe gut effects, aspiration under general anaesthesia, suicidal behaviour and ideation reported with GLP-1 medicines, and the rare optic nerve condition NAION; gallstones are listed among the adverse effects. The Consumer Medicine Information says not to stop Ozempic suddenly because blood sugar may rise.

Orlistat 120 mg for weight control is a Schedule 3 Pharmacist Only Medicine under the Poisons Standard of June 2026, which defines the schedule as substances "the safe use of which requires professional advice but which should be available to the public from a pharmacist without a prescription". In store that means a conversation at the counter. Online, Chemist Warehouse requires a phone call with its pharmacists within five business days and Chemist Outlet within 48 hours, or the item is removed from the order; Chemist Outlet limits each order to one pack and waives the call if a script is supplied. Your Discount Chemist supplies only against a prescription, a retailer policy rather than the law.

Ozempic is a Schedule 4 prescription-only medicine. A doctor, or a nurse practitioner working within their scope of practice and state or territory rules, can prescribe it. For type 2 diabetes within the PBS criteria, the first script needs a telephone or online authority; any other script is private. Prescribing it for weight loss is off-label; newsGP reported in July 2025 that the TGA says it continues to be prescribed off-label. The RACGP's 2022 request that GPs prioritise people with diabetes was tied to the shortage, which ended in July 2025. Healthdirect notes that medicines prescribed for weight loss are not covered by Medicare.

In every indirect comparison available semaglutide produces more weight loss than orlistat (BMJ 2026: subcutaneous semaglutide 9.8% of body weight below lifestyle alone at one year, orlistat "not convincingly different" from lifestyle; Australian Prescriber 2022: semaglutide 0.25 to 1 mg 8.6%, orlistat 4.1%, labelled placebo-subtracted), but no trial has compared them and the Ozempic figures come from diabetes trials. The semaglutide product registered for weight management in Australia is Wegovy, at 2.4 mg; Ozempic is registered for type 2 diabetes. The RACGP's April 2025 review puts incretin medicines first line for people with type 2 diabetes, cardiovascular disease, sleep apnoea, knee osteoarthritis or fatty liver disease, and says orlistat "can be considered in patients with cardiovascular disease or hypertension where incretin-based therapies are not tolerated or unaffordable".

No Australian guideline covers moving from one to the other or taking both. The orlistat Product Information says that, in the absence of interaction studies, "the concomitant administration of orlistat with other anti-obesity agents is not recommended". The Ozempic Product Information says nothing about other weight-loss medicines. No trial of orlistat with semaglutide was found. Orlistat's pharmacokinetic studies found no interaction with phentermine, metformin, statins, fluoxetine, digoxin, phenytoin or nifedipine; semaglutide was not studied.

Neither document gives a changeover procedure. Ozempic has its own starting schedule, 0.25 mg for four weeks then 0.5 mg, and orlistat has a fixed dose, so a switch in either direction means starting the new medicine as a new patient. The RACGP's April 2025 review says to stop and try another agent if a person has lost less than 5% after 12 weeks on the maximum dose, and that most people need ongoing treatment. The Repatriation PBS applies a similar checkpoint to orlistat: 2.5 kg or 2.5% by three to six months.

On stopping: the orlistat document notes possible weight regain after one year, and in the four trials with a second year both orlistat and placebo groups regained similar amounts, so the gap between them held. For semaglutide the regain data come from the 2.4 mg dose: a year after stopping in the STEP 1 extension, the share of people still 5% below their starting weight fell from 86.4% to 48.2%. The Ozempic Consumer Medicine Information adds a diabetes-specific warning: do not stop suddenly, because blood sugar may rise.