Three Pharmacotherapy Categories
Dr. Finkle reviewed three basic categories of anti-obesity medications: Food and Drug Administration–approved short-term and long-term medications and then off-label drugs that can also aid in healthy weight loss. Short-term options include phentermine, diethylpropion, phendimetrazine, and benzphetamine. Long-term options include orlistat, phentermine/topiramate ER, naltrexone HCl/bupropion HCl ER, and the three GLP-1 receptor agonist drugs, liraglutide, semaglutide, and tirzepatide.
The short-term medications are stimulants that increase satiety, but adverse effects can include tachycardia, hypertension, insomnia, dry mouth, constipation, and diarrhea.
These medications are contraindicated for anyone with uncontrolled hypertension, hyperthyroidism, cardiovascular disease, MAOI use, glaucoma, or history of substance use. The goal is a 5% weight loss in 3 months, and 3 months is the maximum prescribing term.
Then Dr. Finkle reviewed the side effects and contraindications for the oral long-term medications. Orlistat, which can aid in up to 5% weight loss, can result in oily stools and fecal incontinence and is contraindicated for people with chronic malabsorption or cholestasis.
Phentermine/topiramate ER, which can aid in up to 10% weight loss, can result in hypertension, paresthesia, or constipation, and is contraindicated for those with glaucoma, hyperthyroidism, and kidney stones. After the starting dose of 3.75 mg/23 mg, Dr. Finkle increases patients’ dose every 2 weeks, ”but if they’re not tolerating it, if they’re having significant side effects, or they’re losing weight, you do not increase the medication.”
Side effects of naltrexone HCl/bupropion HCl ER, which can lead to 5%-6% weight loss, can include hypertension, suicidal ideation, and glaucoma, and it’s contraindicated in those taking opioids or with a history of seizures or anorexia.
The GLP-1 Receptor Agonists
Next Dr. Finkle discussed the newest but most effective medications, the GLP-1 agonists liraglutide, semaglutide, and tirzepatide. The main contraindications for these drugs are a personal or family history of medullary thyroid cancer, multiple endocrine neoplasia type II syndrome, or any hypersensitivity to this drug class. The two main serious risks are pancreatitis — a 1% risk — and gallstones. Though Dr. Finkle included suicidal ideation as a potential risk of these drugs, the most recent evidence suggests there is no link between suicidal ideation and GLP-1 agonists. The most common side effects are nausea, vomiting, diarrhea, constipation, dyspepsia, and an increased heart rate, though these eventually resolve.
“We always start low with these medications,” Dr. Finkle said, and then titrate the dose up each week, “but if they are having awful side effects, just stay on that dose longer.”
The mechanisms of all three drugs for treating obesity are similar; they work to curb central satiety and slow gastric emptying, though they also have additional mechanisms with benefits for blood glucose levels and for the liver and heart.
- Liraglutide, the first of these drugs approved, is a daily subcutaneous injection that starts at a dose of 0.6 mg and goes up to 3 mg. Patients should lose 4% of weight in 16 weeks or else they are non-responders, Dr. Finkle said.
- Semaglutide, a GLP-1 agonist given as a weekly subcutaneous injection, starts at a dose of 0.25 mg and goes up to 2.4 mg; patients should expect a 5% weight loss in 16 weeks if they are responders. Long term, however, patients lose up to an average 15% of body weight with semaglutide; a third of patients lost more than 20% of body weight in clinical trials, compared with 7%-8% body weight loss with liraglutide. An additional benefit of semaglutide is a 20% reduction in risk of cardiovascular disease.
- Tirzepatide is a combined GLP-1 and GIP agonist, also delivered as a weekly subcutaneous injection, that should result in an estimated 5% weight loss in 16 weeks for responders. But tirzepatide is the most effective of the three, with 91% of patients losing at least 5% body weight and more than half of patients (56%) losing at least 20%.