Orlistat

# Orlistat ## Overview - **Classification**: Lipase inhibitor - **Mechanism**: Reversibly inhibits gastric and pancreatic lipases, blocking the breakdown and absorption of ~30% of dietary fat. ## Primary Indications 1. **Weight management**: For obesity, including weight loss and maintenance. 2. **Reduced risk of weight regain**: In conjunction with a reduced-calorie diet. 3. **Improvement of comorbidities**: May help manage obesity-related conditions like type 2 diabetes and dyslipidemia. ## Adult Dosing ### Standard Dosing **Weight Management (Prescription)** - **Dose**: **120 mg** - **Frequency**: Three times daily - **Route**: Oral - **Administration**: Take with each main meal containing fat or up to 1 hour after. - **Maximum dose**: **360 mg/day** **Weight Management (Over-the-Counter - Alli)** - **Dose**: **60 mg** - **Frequency**: Three times daily - **Route**: Oral - **Administration**: Take with each main meal containing fat. - **Maximum dose**: **180 mg/day** ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment needed. Systemic absorption is minimal. - **Hepatic Impairment**: No specific dose adjustment needed. Systemic absorption is minimal. - **Elderly Patients**: No specific dose adjustment required. Monitor for potential polypharmacy and malabsorption. ## Pediatric Dosing ### Neonates (0-28 days) - **Not recommended**: No safety or efficacy data. - **Special Notes**: Obesity in neonates is managed via nutritional and lifestyle interventions. ### Infants (1-12 months) - **Not recommended**: No safety or efficacy data. - **Special Notes**: Focus on nutritional and developmental interventions for weight management. ### Children (1-12 years) - **Indication**: Not FDA approved for children under 12 years. - **Off-label use (under specialist guidance only)**: - **Dose**: **120 mg** - **Frequency**: Three times daily - **Route**: Oral - **Maximum**: **360 mg/day** - **Special Notes**: Use only under strict medical supervision for severe obesity. Closely monitor growth and nutrient intake. ### Adolescents (13-18 years) - **Indication**: Approved for adolescents **≥12 years** with a BMI ≥95th percentile. - **Dose**: **120 mg** - **Frequency**: Three times daily - **Route**: Oral - **Maximum**: **360 mg/day** - **Special Notes**: Must be used with a reduced-calorie diet. Monitor growth, nutritional status, and pubertal development. ## Safety Information ### Contraindications - **Absolute**: Chronic malabsorption syndrome (e.g., Crohn's disease, short bowel syndrome). - **Absolute**: Cholestasis (impaired bile flow). - **Absolute**: Pregnancy and breastfeeding. - **Absolute**: Hypersensitivity to orlistat or formulation components. - **Absolute**: Concomitant use with cyclosporine. ### Common Adverse Effects - **Very Common (>10%)**: Fatty/oily stool, flatulence with discharge, fecal urgency, oily spotting, increased defecation. - **Common (1-10%)**: Headache, abdominal pain/discomfort, influenza, diarrhea, rectal pain/discomfort, nausea, cholelithiasis. - **Serious but Rare**: Severe hepatic injury (e.g., hepatitis, liver failure), severe allergic reactions, acute renal failure (from oxalate nephropathy). ### Key Drug Interactions - **Cyclosporine**: Orlistat significantly reduces cyclosporine absorption. **Contraindicated**. Separate doses by **3 hours** if unavoidable, monitor levels. - **Warfarin/Vitamin K antagonists**: May reduce vitamin K absorption. Monitor INR closely. - **Levothyroxine**: Orlistat can reduce levothyroxine absorption. Separate doses by **4 hours**; monitor thyroid function. - **Fat-soluble vitamins (A, D, E, K)**: Orlistat reduces absorption. Take a multivitamin at least **2 hours before or after** orlistat, or at bedtime. - **Oral Contraceptives**: Diarrhea may reduce efficacy. Advise using an additional barrier method. - **Amiodarone**: Reduced amiodarone absorption. Monitor for efficacy. ## Monitoring & Follow-up - **Before Treatment**: Assess for contraindications (malabsorption, cholestasis). Baseline weight, BMI. - **During Treatment**: Monitor weight loss and BMI. Monitor for GI adverse effects. Monitor INR (if on warfarin) and thyroid function (if on levothyroxine). - **Clinical Signs**: Watch for signs of liver injury (jaundice, dark urine), kidney stones (flank pain, hematuria), or severe allergic reactions. ## Clinical Pearls - 💡 **Dietary Modification is Key**: Orlistat is most effective with a reduced-calorie, low-fat diet. High-fat meals will worsen GI side effects. - 💡 **Vitamin Supplementation**: Advise patients to take a daily multivitamin containing fat-soluble vitamins (A, D, E, K). Take it at least **2 hours before or after** orlistat, or at bedtime. - 💡 **Manage GI Side Effects**: Counsel patients on expected GI effects. Reducing dietary fat intake significantly lessens these symptoms. - 💡 **Not Systemically Absorbed**: This limits systemic side effects but makes it unsuitable for patients with chronic malabsorption. - 💡 **OTC vs. Prescription**: **Alli (60 mg)** is available OTC; **Xenical (120 mg)** is prescription. Ensure patients understand the difference and correct dosing. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.