Orlistat is a potent, reversible inhibitor of gastrointestinal lipases, specifically pancreatic and gastric lipase. It is a peripherally acting anti-obesity agent used for weight management in conjunction with a reduced-calorie diet. It acts locally in the gastrointestinal tract to inhibit the absorption of dietary fats by approximately 30%. It is indicated for individuals with a Body Mass Index (BMI) of 30 kg/m² or greater, or 27 kg/m² or greater in the presence of other risk factors (e.g., hypertension, diabetes, dyslipidaemia).
Adult: One 120mg capsule taken with water immediately before, during, or up to 1 hour after each main meal containing fat. Up to three times daily.
Note: Must be taken with a meal that contains fat to be effective. If a meal is missed or contains no fat, the dose should be omitted. A daily multivitamin supplement containing fat-soluble vitamins (A, D, E, K and beta-carotene) should be taken at least 2 hours before or after orlistat administration to prevent deficiency.
Orlistat is a potent, specific, and reversible inhibitor of gastrointestinal lipases, primarily pancreatic and gastric lipase. These enzymes are essential for the hydrolysis of dietary triglycerides into absorbable free fatty acids and monoglycerides. By covalently binding to the active serine site of these lipases, orlistat inactivates them within the lumen of the stomach and small intestine. This prevents the breakdown and subsequent absorption of approximately 30% of ingested dietary fat, which is then excreted unchanged in the feces.
Pregnancy: Category X. Contraindicated. Weight loss offers no potential benefit to a pregnant woman and may cause fetal harm.
Driving: No known effects. However, patients experiencing dizziness or fatigue should exercise caution.
| Cyclosporine | Orlistat can significantly reduce cyclosporine absorption, leading to subtherapeutic levels. Monitor levels closely. | Major |
| Warfarin/Acenocoumarol | Potential for altered INR. Orlistat may affect vitamin K absorption. Monitor INR frequently. | Major |
| Levothyroxine | Possible decreased levothyroxine efficacy, leading to hypothyroidism. Administer at least 4 hours apart. | Moderate |
| Antiepileptics (e.g., Valproate, Lamotrigine) | Theoretical risk of reduced absorption. Monitor efficacy. | Moderate |
| Antiretroviral drugs (e.g., Atazanavir, Lopinavir) | Possible reduced absorption of lipophilic antiretrovirals. Avoid concomitant use. | Major |
| Amiodarone | Potential for reduced absorption. Monitor clinical effect. | Moderate |
| Fat-soluble Vitamin Supplements (A, D, E, K, Beta-carotene) | Orlistat reduces their absorption. Administer supplements at least 2 hours before or after orlistat. | Moderate |