Alli vs. Xenical

Are Alli and Xenical the Same Thing?

Orlistat and Xenical are gastrointestinal lipase inhibitors used to help with weight loss by preventing the digestion and absorption of fat in food by inhibiting the enzyme lipase in the intestine.

Xenical is a brand name for orlistat. Another brand name for orlistat is Alli.

What Are Possible Side Effects of Alli?

Common side effects of Alli include:

  • changes in your bowel function because of the unabsorbed fat,
  • fatty/oily stool,
  • oily spotting in your undergarments,
  • orange or brown colored oil in your stool,
  • intestinal gas with discharge,
  • loose stools,
  • a feeling of needing to have a bowel movement right away,
  • increased number of bowel movements,
  • poor bowel control,
  • stomach pain,
  • nausea,
  • vomiting,
  • diarrhea, or
  • rectal pain.

These side effects of Alli may worsen if you eat more fat than you should. Other side effects of Alli include:

Stop taking Alli and tell your doctor if you have rare but serious side effects including:

  • symptoms of liver disease (such as persistent nausea and vomiting, severe stomach or abdominal pain, dark urine, yellowing eyes or skin), or
  • symptoms of kidney stones (such as back pain, pain when urinating, pink or bloody urine).

What Are Possible Side Effects of Xenical?

Common side effects of Xenical include:

  • oily spotting on underwear
  • flatulence
  • urgent bowel movements
  • fatty or oily stools
  • increased number of bowel movements
  • inability to control bowel movements
  • gas with discharge
  • loose stools
  • stomach pain
  • nausea
  • vomiting
  • diarrhea
  • rectal pain
  • weakness,
  • dark urine
  • clay-colored stools
  • itching
  • loss of appetite
  • jaundice (yellowing of the skin or eyes)
  • problems with your teeth or gums
  • cold symptoms (stuffy nose, sneezing, cough, fever, chills, sore throat, flu symptoms)
  • headache
  • back pain, or
  • skin rash.

Tell your doctor if you experience serious side effects of Xenical including blood in your urine, urinating less than usual or not at all, drowsiness, confusion, mood changes, increased thirst, swelling, weight gain, feeling short of breath, severe pain in your upper stomach spreading to your back, or fast heart rate.


Surprising Causes of Weight Gain See Slideshow

What Is Alli?

Alli (orlistat) Capsules works by blocking absorption of 25% of the fat in a meal and is used for weight loss in overweight adults, 18 years and older, when used along with a reduced-calorie and low-fat diet.

What Is Xenical?

Xenical (orlistat) is a gastrointestinal lipase inhibitor used to help with weight loss by preventing the digestion and absorption of fat in food by inhibiting the enzyme lipase in the intestine.

What Drugs Interact With Alli?

Alli may interact with warfarin, cyclosporine and medicines for thyroid disease. Tell your doctor all prescription and over-the-counter medications and supplements you use.

What Drugs Interact With Xenical?

Xenical may reduce the absorption and blood levels of cyclosporine when both drugs are administered together. Xenical may also cause vitamin K levels to decline, and patients taking warfarin (Coumadin) must have their blood clotting monitored closely.

How Should Alli Be Taken?

The recommended dose of Alli for overweight adults 18 years and older is 1 60-mg capsule with each meal containing fat, not to exceed 3 capsules daily. Use with a reduced-calorie, low-fat diet.

How Should Xenical Be Taken?

Xenical is taken as oral capsules.


All drug information provided on is sourced directly from drug monographs published by the U.S. Food and Drug Administration (FDA).

Any drug information published on regarding general drug information, drug side effects, drug usage, dosage, and more are sourced from the original drug documentation found in its FDA drug monograph.

Drug information found in the drug comparisons published on is primarily sourced from the FDA drug information. The drug comparison information found in this article does not contain any data from clinical trials with human participants or animals performed by any of the drug manufacturers comparing the drugs.

The drug comparisons information provided does not cover every potential use, warning, drug interaction, side effect, or adverse or allergic reaction. assumes no responsibility for any healthcare administered to a person based on the information found on this site.

As drug information can and will change at any time, makes every effort to update its drug information. Due to the time-sensitive nature of drug information, makes no guarantees that the information provided is the most current.

Any missing drug warnings or information does not in any way guarantee the safety, effectiveness, or the lack of adverse effects of any drug. The drug information provided is intended for reference only and should not be used as a substitute for medical advice.

If you have specific questions regarding a drug’s safety, side effects, usage, warnings, etc., you should contact your doctor or pharmacist, or refer to the individual drug monograph details found on the or websites for more information.

You may also report negative side effects of prescription drugs to the FDA by visiting the FDA MedWatch website or calling 1-800-FDA-1088.


GSK. Alli Product Information.
H2-Pharma, LLC. Xenical Product Information.

Health Solutions From Our Sponsors