Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is the mechanism of action of Orlistat?

1. Inhibits insulin secretion

2. Decreases gastrointestinal absorption of carbohydrates

3. Inhibits pancreatic lipase

4. Stimulates appetite suppression

The correct answer is: Inhibits pancreatic lipase

Orlistat works primarily by inhibiting pancreatic lipase, an enzyme critical for the digestion of dietary fats. This action prevents the breakdown of triglycerides into free fatty acids and glycerol, leading to a significant reduction in fat absorption in the gastrointestinal tract. Because undigested fats are not absorbed, they are instead excreted, which contributes to weight loss in individuals taking the medication. The mechanism of action is directly related to its use in managing obesity, as it allows patients to consume a diet that is higher in fat without absorbing the full caloric content. This results in a decrease in overall caloric intake, fostering weight loss over time. While the other options involve processes related to appetite, insulin, or carbohydrate absorption, they do not correctly describe the specific mechanism through which Orlistat exerts its effects. Instead, its unique action focuses on the inhibition of lipase, making it effective for promoting weight loss by limiting fat intake.