Xenical. The new wonder drug?

Xenical, the new drug being hailed as the answer to obesity, was recently launched for use in Australia by Roche Pharmaceuticals. 'Xenical' is the brand name given to orlistat (a gastrointestinal lipase inhibitor) by Roche. Many controlled trials were undertaken to test it's use and safety before the drug was released.

Xenical works by inhibiting fat absorption in obese patients. It acts in the small intestine to inhibit fat absorption by up to 30%. It is taken in the form of a capsule three times a day with meals, along with a nutritious, reduced calorie diet (less than 30% energy from fat). Increased doses of Xenical do not increase it's effectiveness. Excess fat which is not absorbed is primarily excreted in the faeces. Although Xenical does aid weight loss in morbidly obese people, there are a number of side effects to be aware of. The most commonly reported side effects which include oily spotting, flatus with discharge, faecal urgency and fatty stools, are often reported in the early stages of treatment, as patients learn to avoid eating fat while taking this drug. There is also some loss of fat soluble vitamins
in the faeces due to the fat malabsorption and some patients had lowered levels of vitamins A, D E, and K to the lower end of the normal range. Some patients dropped below the normal range if their diet was lacking in these nutrients before commencing the medication. Therefore vitamin levels need to be monitored in patients taking Xenical. In some cases, vitamin supplements may be necessary to maintain normal levels.

Studies have been conducted which assess the effectiveness of orlistat compared with a placebo control. These studies reported increased weight loss in patients taking orlistat with an energy controlled diet. These same studies, however, recommend that the use of orlistat for a period longer than two years needs to be monitored due to the risk of adverse side effects. A study by Davidson and colleagues (1999) found that serum insulin levels remained low after two year treatment with orlistat, and suggested that orlistat may also be useful in improving insulin resistance. Orlistat has also been shown to reduce cholesterol levels.

It is currently recommended that prescription of Xenical be restricted to those people who are clinically diagnosed as being obese (BMI above 30), and people who have a BMI over 27 with one or more other risk factors being associated with overweight such as diabetes, high blood pressure or high cholesterol. Prescription of Xenical comes with the recommendation that patients participate in a support program which includes regular telephone contact with a Roche health professional to ensure that the medication is embedded in a lifestyle program of healthy eating and physical activity.

A resource kit is given to each patient which includes information about Xenical, a selection of low fat recipes, a food diary, a goal planner, a fat, fibre and carbohydrate counter and a pedometer. Also included in this package is a monthly newsletter with information about eating out, reading food labels, and practical ideas about including physical activity in daily life.

While these support mechanisms will no doubt be useful to obese patients, it is also recommended that doctors, when prescribing Xenical to patients, also refer them to an Accredited Practising Dietitian who will be able to give appropriate dietary advice.

References

• Davidson, M.H. Haupton, J. DiGirolamo, M. Foreyt, J.P. Halsted, C.H. Heber, D.
  Heimburger, D.C. Lucas, C.P. Robbins, D.C. Chung, J. Heymsfield, S.B. (1999) Weight control and risk factor reduction in obese subjects treated for 2 years with orlistat. JAMA. 281;3: 235-242.
  
• Sjostrom, L. Rissanen, A. Andersen, T. Boldrin, M. Golay, A. Koppeschaar, H.P.F. Krempf, M. (1998) Randomised placebo-controlled trial of orlistat for weight loss and prevention of weight regain in obese patients. Lancet. 352: 167-172.
  
• Roche Pharmaceuticals. (1999) Patient information about XENICAL (orlistat) capsules.
  
• Orlistat. Medication for obesity. (1999) MayoClinic.
  

Last Updated: April 5, 2001