Orlistat - Side Effects

Side Effects

The primary side effects of the drug are gastrointestinal-related, and include steatorrhea (oily, loose stools with excessive flatus due to unabsorbed fats reaching the large intestine), fecal incontinence and frequent or urgent bowel movements. GlaxoSmithKline recommends that all users be cautious of the possible side effects until they "have a sense of any treatment effects". To minimize these effects, foods with high fat content should be avoided; the manufacturer advises consumers to follow a low-fat, reduced-calorie diet. Oily stools and flatulence can be controlled by reducing the dietary fat content to somewhere in the region of 15 grams per meal. The manual for Alli makes it clear that orlistat treatment involves aversion therapy, encouraging the user to associate eating fat with unpleasant treatment effects.

According to Roche, side effects are most severe when beginning therapy and may decrease in frequency with time; this is supported by the results of the XENDOS study, which found that only 36% of people had gastrointestinal adverse effects during their fourth year of taking orlistat, whereas 91% of study subjects had experienced at least one GI-related side effect during the first year of treatment. It has also been suggested that the decrease in side effects over time may be associated with long-term compliance with a low-fat diet.

The side effect profile of orlistat led US consumer group Prescription Access Litigation (PAL) to award its first 2007 "Bitter Pill Award" to GlaxoSmithKline—the 'With Allies Like This, Who Needs Enemas?' Award.

On 26 May 2010, the U.S. Food and Drug Administration (FDA) approved a revised label for Xenical to include new safety information about cases of severe liver injury that have been reported rarely with the use of this medication.

An analysis of over 900 orlistat users in Ontario showed that their rate of acute kidney injury was more than triple that of non-users. The putative mechanism for this effect is postulated to be excessive oxalate absorption from the gut and its subsequent deposition in the kidney, with excessive oxalate absorption being a known consequence of fat malabsorption.