Medication Overview

Xenical (Orlistat) is a prescription medication used to aid weight loss in individuals who are overweight or obese. It works by inhibiting the absorption of dietary fats. Orlistat does not chemically alter the brain; rather, it targets fat breakdown in the gastrointestinal tract.

Composition and Formulation

Xenical contains the active ingredient Orlistat, which is a gastrointestinal lipase inhibitor. Each Xenical capsule typically includes 120 mg of Orlistat. Other inactive ingredients include microcrystalline cellulose, sodium starch glycolate, and talc, ensuring proper capsule formation and stability.

Mechanism of Action

Orlistat acts locally in the gut to inhibit lipase, an enzyme necessary for the breakdown of triglycerides in the intestine. When lipase activity is blocked, triglycerides from the diet are not hydrolyzed into absorbable free fatty acids and monoglycerides. Consequently, undigested triglycerides pass out of the body in the feces, leading to reduced fat absorption and caloric intake.

Indications for Use

Xenical is indicated for weight loss in patients with an initial body mass index (BMI) of 30 kg/m² or greater. It can also be used in patients with a BMI of 27 kg/m² or more if they have other risk factors such as hypertension, diabetes, or dyslipidemia. It is prescribed as part of a comprehensive weight management program that includes a calorie-controlled diet and physical activity.

Dosage and Administration

The recommended dose of Xenical is one 120 mg capsule taken three times a day with each main meal containing fat (during or up to one hour after the meal). Patients should adhere to a nutritionally balanced, mildly hypocaloric diet that contains approximately 30% of calories from fat. The daily intake of fat, carbohydrates, and protein should be distributed over three main meals.

Metabolism and Excretion

Orlistat undergoes minimal systemic absorption, remaining primarily in the gastrointestinal tract. The absorbed portion is mainly metabolized within the intestinal wall, and the excreted metabolites are primarily eliminated via the feces. Around 97% of an administered dose is excreted unchanged in feces, with less than 2% excreted in urine.

Potential Drug Interactions

Orlistat may interfere with the absorption of certain medications. For instance, it can decrease the absorption of fat-soluble vitamins such as A, D, E, and K. It is advisable for patients to take a multivitamin supplement at least two hours before or after Xenical to mitigate this effect. Additionally, it may affect the bioavailability of drugs such as cyclosporine and levothyroxine; hence, these should be administered at least four hours apart from Orlistat.

Contraindications

Xenical is contraindicated in patients with chronic malabsorption syndrome, cholestasis, and known hypersensitivity to Orlistat or any of the inactive ingredients of the formulation. Patients with anorexia or bulimia should not use Orlistat due to the risk of nutritional deficiencies.

Side Effects Profile

Common side effects of Xenical include gastrointestinal issues such as oily spotting, flatus with discharge, fecal urgency, fatty/oily stool, and frequent bowel movements. These effects are a direct consequence of the excretion of unabsorbed fat in the stool. Some patients may also experience stomach pain or discomfort and headache.

Monitoring Parameters

Patients on Xenical should be monitored for weight loss efficacy and potential nutritional deficiencies. Regularly measuring weight, BMI, and waist circumference can help track progress. Laboratory tests such as serum lipid profiles, glucose levels, and vitamin levels (A, D, E, and K) should be evaluated periodically to detect and manage potential side effects and ensure nutritional adequacy.

Storage Conditions

Store Xenical at room temperature between 15°C to 25°C (59°F to 77°F). Keep the medication in its original container to protect it from moisture and heat. Ensure that the container is tightly closed when not in use, and keep out of reach of children and pets.

Special Populations

Special consideration should be given to elderly patients, those with hepatic impairment, and those with renal insufficiency. In the elderly, dosing adjustments are generally not necessary, but monitoring is advised. Patients with hepatic or renal impairments should use Xenical cautiously, though specific dose adjustments may not be required. Pregnant and breastfeeding women should consult with a healthcare provider as the safety profile for these populations is not well-established.