Hi, Xenical contains orlistat that is used to treat obesity and reduce obesity related complications such as high blood pressure or hypertension, diabetes mellitus, hyperlipidemia etc. It works by blocking some of the fat from being absorbed by the body. For that reason, it is used to help obese person lose body weight, weight maintenance as well as keep this weight off. A reduced calorie diet should be used along with Xenical during weight reduction program. Irregular menstrual cycles may be noticed in women during taking Xenical. In the first few weeks after starting to take Xenical, menstrual irregularities are commonly found. In some women, irregularities in the menstrual periods last for as long as they are taking Xenical. If these menstrual irregularities bother you, then you should inform your prescribing doctor first for medical help. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician