Alli® Weight Loss Medication & Warfarin

Publication Date: 
Tue, 08/13/2013
By: Alere Staff

People have long looked to medication or supplements to help them lose weight. In recent years, Alli®drug has become popular with overweight individuals. The Alli®drug is the reduced-strength version of orlistat (Xenical) at 60 milligrams versus 120 milligrams, a prescription drug used to treat obesity.1 The drug works by blocking the absorption of fat in the intestines and therefore causes weight loss when combined with a low-fat diet and exercise.

Alli®medicine promotes weight loss by preventing an enzyme called lipase from breaking down the fat while it’s still being digested. The undigested fat then continues through the intestines and is eliminated through bowel movements. As a result, there may be some bowel changes after starting Alli®medication.

According to the manufacturer, Alli®medication blocks about 25% of the fat eaten from being absorbed.2 A study conducted by Dr. James Anderson of the University of Kentucky and presented at the 2005 annual meeting of NAASO, the Obesity Society in Vancouver, British Columbia shows that during a course of four months, overweight people who were on a low calorie and low fat diet and also used the drug lost 5% of their baseline weight and those who were on diet only lost 3.3%.3 Researchers cautioned its use as no long term studies have been completed.

Among various digestive side effects, Alli®medication can also decrease the absorption of certain fat-soluble vitamins, including vitamins D, E and K. Vitamin K plays a significant role in maintaining stable INR test results for those taking warfarin (or brand of warfarin such as Coumadin®). The U.S. Food & Drug Administration (FDA) recommends patients who take the Alli®drug also consider taking a multivitamin. If you are taking warfarin, talk to your doctor before taking a multivitamin.

Patients taking warfarin should test their INR more frequently as an increase in INR test results can be expected due to the inhibition of vitamin K. An increased INR is closely associated with an increase in bleeding risk.4

After weighing the side effects and interaction with warfarin, you may be better off eating a healthy diet and going for a walk on a regular basis for weight control. Talk to your doctor about your desire to lose weight and develop a weight loss and exercise plan together.

  1. Anderson JW. Orlistat for the management of overweight individuals and obesity: A review of potential for the 60-mg, over-the-counter dosage. Expert Opinions in Pharmacotherapy. 2007;8:1733.
  2. Diet-related side effects. Accessed June 6, 2013.
  3. Anderson JW, et al. Low-dose orlistat effects on body weight of mildly to moderately overweight individuals: A 16-week, double-blind, placebo controlled trial. Annals of Pharmacotherapy. 2006;40:1717.
  4. Bristol-Myers Squibb Company. Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb Company. 2009.


COUMADIN® is a registered trademark of Bristol-Myers Squibb Pharma Company. Alere is not affiliated or associated with Bristol-Myers Squibb Pharma Company or the COUMADIN® trademark.