The pathophysiology of faecal spotting in obese subjects during treatment with orlistat

Aliment Pharmacol Ther. 2004 Feb 1;19(3):311-21. doi: 10.1111/j.1365-2036.2004.01848.x.


Background: The intermittent loss of oil or liquid faeces ('spotting') is an adverse effect that occurs in obese patients during treatment with the lipase inhibitor orlistat; the pathophysiology is unknown.

Aim: To investigate the effects of orlistat on anorectal sensorimotor function and continence.

Methods: Obese subjects susceptible to spotting were identified by an unblind trial of orlistat. Obese spotters (n = 15) and non-spotters (n = 16) completed a randomized, double-blind, cross-over trial of orlistat and placebo. Anorectal function was assessed by rectal barostat and anal manometry, together with a novel stool substitute retention test, a quantitative measurement of faecal continence.

Results: Orlistat increased stool volume and raised faecal fat and water. Treatment had no effect on anorectal motor function, but rectal sensation was reduced; on retention testing, the volume retained was increased. Subjects susceptible to spotting had lower rectal compliance, heightened rectal sensitivity and weaker resting sphincter pressure than non-spotters. On retention testing, gross continence was maintained; however, spotters lost small volumes of rectal contents during rectal filling.

Conclusion: Treatment with orlistat has no direct adverse effects on anorectal function or continence. Spotting occurs during treatment with orlistat when patients with sub-clinical anorectal dysfunction are exposed to increased stool volume and altered stool composition.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-Obesity Agents / adverse effects*
  • Cross-Over Studies
  • Double-Blind Method
  • Fecal Incontinence / chemically induced*
  • Fecal Incontinence / physiopathology
  • Feces / chemistry
  • Female
  • Humans
  • Lactones / adverse effects*
  • Male
  • Manometry / methods
  • Medical Records
  • Middle Aged
  • Obesity / drug therapy*
  • Orlistat
  • Prospective Studies
  • Reproducibility of Results


  • Anti-Obesity Agents
  • Lactones
  • Orlistat