A 34-year-old woman comes to the office due to inability to lose weight despite diet and exercise. She reports that she gained a significant amount of weight after she stopped smoking 4 years ago. The patient has tried several commercial weight-loss diet programs in the last year without success. She wants to lose at least 4.5 kg (10 lb) over the next few months before she gets married. The patient does not have any other medical conditions and takes no medications. Blood pressure is 122/80 mm Hg and pulse is 78/min. BMI is 33 kg/m². Physical examination shows an obese habitus but is otherwise unremarkable. Laboratory testing for secondary causes of weight gain is unrevealing. In addition to encouraging continued efforts at lifestyle change, the physician prescribes a short course of oral phentermine for weight loss. The weight loss induced by this medication is caused by which of the following mechanisms?

Question

Quizplus · Accepted Answer

11ec160b_3bc0_b988_9249_0f66a878dedd_MD0001_00 Norepinephrine-releasing agents (eg, phentermine) are sympathomimetic weight-loss drugs indicated for short-term (≤12 weeks) treatment of obesity. They work by stimulating release and inhibiting reuptake of norepinephrine and, to a lesser extent, serotonin and dopamine. Subjective effects include an increased sensation of satiety and subsequently reduced caloric intake. Because of the increased sympathetic activity associated with these drugs, they can raise blood pressure and should be avoided in patients with comorbid hypertension or heart disease. Norepinephrine-releasing agents can induce brisk initial weight loss but are notable for poor long-term benefit, and most patients regain the lost weight following discontinuation. (Choice A) Glucagonlike peptide-1 (GLP-1) agonists (eg, liraglutide) increase glucose-dependent insulin secretion and are most commonly used in treatment of type 2 diabetes mellitus. In addition, GLP-1 agonists cause delayed gastric emptying and decreased appetite, leading to weight loss. (Choice B) Orlistat is an intestinal lipase inhibitor. It acts by reducing the digestion and subsequent absorption of dietary fats. The increased residual fat content in the intestinal lumen can lead to intestinal discomfort, diarrhea, fecal incontinence, and impaired absorption of fat-soluble vitamins (eg, vitamin D). (Choice C) Naltrexone is an opioid antagonist indicated for the treatment of opioid abuse and alcohol dependence. It is also used in a combination pill with bupropion for weight loss, in which it is thought to potentiate the otherwise minor weight-loss effects of bupropion. (Choice D) In addition to treating depression and anxiety, selective serotonin reuptake inhibitors (SSRIs) (eg, fluoxetine) are commonly used in the treatment of eating disorders, especially bulimia nervosa. Although some patients taking SSRIs experience minor weight loss, the effects on weight are variable, and these medications are not prescribed for weight loss. Educational objective: Norepinephrine-releasing agents (eg, phentermine) are sympathomimetic weight-loss drugs indicated for short-term treatment of obesity. They stimulate the release and inhibit the reuptake of norepinephrine. Subjective effects include an increased sensation of satiety, leading to reduced caloric intake. Weight regain after cessation is common with these drugs. __________ References: Obesity pharmacotherapy. (http://www.ncbi.nlm.nih.gov/pubmed/29156182)

A 34-Year-Old Woman Comes to the Office Due to Inability