1. Clinical Overview
Orlistat 60mg is a peripherally acting anti-obesity agent, classified as a lipase inhibitor. It is indicated for weight management in conjunction with a reduced-calorie diet. It acts locally in the gastrointestinal tract to inhibit dietary fat absorption by approximately 30%. In India, it is widely used as an over-the-counter (OTC) aid for weight loss in adults with a Body Mass Index (BMI) of 25 kg/m² or above.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 24 to 48 hours (onset of fat malabsorption). | The pharmacodynamic effect (fat malabsorption) lasts for the duration of drug presence in the GI tract, typically correlating with its dosing schedule. | <1% (systemic absorption is minimal). |
2. Mechanism of Action
Orlistat is a potent, 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 in the gastric and intestinal lumen, orlistat inactivates them. This prevents the digestion of approximately 30% of ingested dietary fat, which is then excreted unchanged in the feces.
3. Indications & Uses
- Weight management in adults with a Body Mass Index (BMI) ≥ 25 kg/m², in conjunction with a reduced-calorie diet.
- Aid to weight loss and to reduce the risk of weight regain in obese or overweight individuals.
4. Dosage & Administration
Adult Dosage: One 60mg capsule taken orally three times daily with each main meal containing fat (during or up to 1 hour after the meal). If a meal is missed or contains no fat, the dose should be omitted.
Administration: Take with a glass of water. Should be taken during or within 1 hour of a main meal. Daily fat intake should be distributed over three main meals. A daily multivitamin supplement containing fat-soluble vitamins (A, D, E, K) should be taken at least 2 hours before or after orlistat (e.g., at bedtime).
5. Side Effects
Common side effects may include:
- Oily spotting from the rectum
- Flatus with discharge
- Fecal urgency
- Fatty/oily stool
- Oily evacuation
- Increased defecation
- Fecal incontinence
- Abdominal pain/discomfort
- Liquid stools
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Cyclosporine | Orlistat may significantly decrease cyclosporine absorption, reducing its plasma levels and efficacy. Risk of transplant rejection. | Major |
| Levothyroxine | Orlistat may decrease levothyroxine absorption, potentially causing hypothyroidism. Dosing should be separated by at least 4 hours. | Major |
| Warfarin/Acenocoumarol | Orlistat may affect vitamin K absorption, potentially altering INR. Monitor INR closely, especially when starting or stopping orlistat. | Major |
| Antiepileptics (e.g., Valproate, Lamotrigine) | Potential for reduced absorption and decreased efficacy. Monitor seizure control. | Moderate |
| Antiretroviral drugs (e.g., Atazanavir, Lopinavir) | Potential for reduced absorption. Avoid concomitant use. | Major |
| Amiodarone | Potential for reduced absorption. Monitor efficacy. | Moderate |
| Fat-soluble Vitamins (A, D, E, K) and Beta-carotene | Orlistat reduces their absorption. Supplementation is required, taken at a 2+ hour separation. | Moderate |
7. Patient Counselling
- DO take the capsule with each main meal containing fat, or up to 1 hour after.
- DO follow a balanced, reduced-calorie diet where no more than 30% of calories come from fat.
- DO take a daily multivitamin supplement at least 2 hours before or after orlistat (e.g., at bedtime).
- DO maintain adequate fluid intake.
- DO engage in regular physical activity (e.g., 30 minutes of brisk walking most days).
- DON'T take the capsule if you skip a meal or eat a fat-free meal.
- DON'T take a double dose to make up for a missed one.
- DON'T consume a high-fat diet (>30% fat calories), as this will worsen side effects.
8. Toxicology & Storage
Overdose: Acute overdose is unlikely to produce systemic effects due to minimal absorption. Expected effects would be an exacerbation of gastrointestinal adverse effects (severe oily stools, diarrhea, abdominal pain). Cases of subacute bowel obstruction have been reported with very high doses.
Storage: Store below 25°C. Protect from moisture. Keep the container tightly closed. Keep out of reach of children.