Key takeaways
Phentermine (Adipex-P) and tirzepatide (Zepbound) are both medications used for weight management, but they belong to different drug classes and have distinct characteristics. Phentermine is a sympathomimetic stimulant taken orally, typically once a day, and is FDA-approved for short-term weight management in adults with a body mass index (BMI of) 30 kg/m² or greater, or 27 kg/m² with a weight-related condition. In contrast, tirzepatide is a GIP and GLP-1 agonist injected under the skin once a week. It is approved for long-term weight management and moderate-to-severe sleep apnea in adults living with obesity. Phentermine is available in various oral forms, including tablets and capsules, and is a controlled substance due to its potential for misuse and dependence. Tirzepatide is available as a prefilled pen and is not a controlled substance. Common phentermine side effects include dry mouth and trouble sleeping, while tirzepatide often causes nausea and diarrhea. Phentermine should not be combined with other weight loss medications. Tirzepatide can interact with diabetes medications and affect how well birth controll pills work. Both medications require a prescription and should be used alongside diet and exercise for the best results.
