Overview
Orlistat is a gastrointestinal lipase inhibitor used for obesity management in conjunction with a reduced-calorie diet. It promotes weight loss and maintenance by blocking dietary fat absorption. It is indicated for patients with BMI ≥30 kg/m² or ≥27 kg/m² with comorbidities like hypertension or diabetes.
Mechanism of Action
Orlistat is a reversible inhibitor of gastric and pancreatic lipases, enzymes that hydrolyze triglycerides into absorbable free fatty acids and monoglycerides. By inhibiting these enzymes in the lumen of the stomach and small intestine, it decreases systemic absorption of dietary fat by approximately 30%.
Indications
- Obesity management including weight loss and weight maintenance when used with a reduced-calorie diet
- Reduction of risk for weight regain after prior weight loss
- Treatment of obese patients with BMI ≥30 kg/m² or ≥27 kg/m² with other risk factors (e.g., hypertension, diabetes, dyslipidemia)
Common Doses
- 120 mg
Dosage
120 mg orally three times daily with each main meal containing fat. Dose should be taken during the meal or up to one hour after eating. If a meal is missed or contains no fat, the dose can be omitted.
Contraindications
- Pregnancy
- Chronic malabsorption syndrome
- Cholestasis
- Known hypersensitivity to orlistat or any component of the product
Side Effects
- Oily spotting
- Flatus with discharge
- Fecal urgency
- Fatty/oily stool
- Increased defecation
- Fecal incontinence
- Abdominal pain/discomfort
- Nausea
- Infections (upper respiratory, influenza-like symptoms)
- Headache
- Back pain
- Menstrual irregularities
Interactions
- Cyclosporine - administer at least 2 hours apart
- Warfarin - monitor INR closely as orlistat may affect vitamin K absorption
- Levothyroxine - administer at least 4 hours apart
- Antiretroviral drugs (especially HIV protease inhibitors) - may reduce absorption
- Amiodarone - potential interaction with fat-soluble drug
Counseling Points
- Take with meals containing fat (up to 30% of calories from fat)
- If meal is missed or contains no fat, skip dose
- Take multivitamin containing fat-soluble vitamins daily at least 2 hours before or after orlistat
- Maintain reduced-calorie diet with approximately 30% of calories from fat
- Report severe abdominal pain, yellowing of skin/eyes, or dark urine immediately
- Common gastrointestinal effects are typically mild and decrease over time