There is only has one true competitor to Xenical when it comes to its place as a weight loss medication and it is one of only two weight loss medications that have been approved by the United States Food and Drug Administration. The biggest difference between Xenical and its competitor Reductil has more to do with side effects than anything else.

Xenical has very few known side effects,  this is because Xenical works by blocking the absorption of dietary fat so it is likely that you will experience some changes in bowel habits. These changes are a natural effect of blocking the fat from being absorbed and generally occur during the first weeks of treatment; however, for some people they may continue for up to 6 months or longer during treatment with Xenical. These changes may include an oily discharge associated with gas, an increased number of bowel movements, with increased urgency and possibly an inability to control them, particularly after meals containing higher amounts of fat than are recommended. Naturally the effects vary from person to person.

Reductil has had some serious side effects  which have been reported and studies are ongoing into reports of sudden death, heart failure, renal failure and gastrointestinal problems. The FDA is looking into these reports and Reductil is still available on the market.

Reductil side effects which have been  encountered were dry mouth, paradoxically increased appetite, nausea, strange taste in the mouth, upset stomach, constipation, trouble sleeping, dizziness, drowsiness, menstrual cramps, headache, flushing, or joint/muscle pain.

Some infrequently reported but serious side effects reported included cardiac arrhythmias, par aesthesia, and mood changes such as excitement, restlessness, confusion and depression.  

Xenical clearly has fewer reported side effects but as with any drug Xenical patients may experience some. Xenical shouldn't be taken if you are pregnant, nursing, have food absorption problems or reduced bile flow. It is unknown what effects Xenical may have on an unborn child and for those with food absorption issues; you may not be getting the proper nutrients.

If you are taking cyclosporine, speak to your doctor before taking Xenical as these need to be taken separately at least two hours apart so that they do not affect each other.