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Also: Alli · Beacita · tetrahydrolipstatin · Ro 18-0647 · the fat blocker
Four separate measurements, never averaged. Independent evidence counts only studies with no sponsor attached. Methodology version v2.0-2026-10 · how we grade evidence
The oldest weight-loss drug still widely sold, and the first the FDA ever approved for over-the-counter use. Marketed as an adjunct to a mildly hypocaloric diet. Its four-year pivotal trial additionally claimed a reduction in progression to type 2 diabetes.
Its mechanism is the best-confirmed in this entire library and its efficacy is the weakest. Faecal fat excretion is directly measurable, so there is no doubt about what the drug does. The doubt is about whether it matters: the placebo-adjusted difference in its own pivotal trial fell from 4.4 kg at one year to 2.8 kg at four years, with 48% of the drug arm not completing. Independent meta-analysis puts the pooled advantage at 2.9 kg, and the 2026 network meta-analysis found it not convincingly different from lifestyle modification alone.
Gastrointestinal effects are near-universal rather than occasional, and are the reason most people stop.
At a glance
Binds covalently to the active serine site of gastric and pancreatic lipases in the gut lumen, blocking hydrolysis of dietary triglycerides into absorbable free fatty acids and monoglycerides. The unabsorbed fat is excreted, reducing calories absorbed. It is minimally absorbed itself, so the action is essentially local to the gut — which is also why its adverse effects are overwhelmingly gastrointestinal, and why fat-soluble vitamin levels fall.
Dated determinations, each flagged for whether it is final and whether it covers safety only. A safety review is not an efficacy finding, and most reporting in this category conflates the two.
The FDA began an early safety review of liver injury on 24 August 2009 after 32 reports of serious liver injury including six of liver failure between 1999 and October 2008, and approved revised labelling on 26 May 2010. The agency stated no definite causal link had been established. This is a safety signal from spontaneous reports, categorically different from a trial finding. A further label change warning of acute kidney injury was approved on 10 June 2026.
Prescription Xenical was approved on 23 April 1999 under NDA 020766. The lower-strength over-the-counter form followed on 7 February 2007.
Authorised 29 July 1998 and renewed in 2003 and 2008, in conjunction with a mildly hypocaloric diet. Originally held by Roche Registration Limited, now by Cheplapharm Arzneimittel GmbH.
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