Zepbound vs. Adipex
See how Zepbound and Adipex compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Zepbound is a once-weekly injected GLP-1/GIP medicine approved for long-term weight management, while Adipex is a once-daily stimulant pill approved only for short-term use.
Zepbound's main side effects are gastrointestinal, while Adipex's main side effects involve the nervous system, like insomnia and jitteriness.
Adipex costs far less per month than Zepbound but is a controlled substance not meant for use beyond a few weeks.
Zepbound vs. Adipex Drug Summary
Zepbound
Zepbound (tirzepatide) is a GLP-1/GIP receptor agonist given as a once-weekly subcutaneous injection. It is FDA-approved for chronic weight management in adults with obesity or with overweight plus a weight-related condition, and separately for moderate-to-severe obstructive sleep apnea in adults with obesity. Dosing starts low and increases gradually over several months to reduce stomach side effects.
Adipex
Adipex (phentermine) is a sympathomimetic amine, essentially a stimulant, taken as an oral tablet once or twice daily. It is FDA-approved only as a short-term add-on to diet and exercise for weight loss, meant to be used for just a few weeks. It has been prescribed since 1959 and is a Schedule IV controlled substance.
Zepbound vs. Adipex Side Effects
Zepbound
Adipex
Zepbound vs. Adipex Dosage
Zepbound
Adipex
| STAGE | DOSE | WHEN |
| Starting dose | 2.5 mg once weekly | Weeks 1-4 |
| Maximum dose | 15 mg once weekly | Week 21 onward |
| Dose changes | 5 increases | Every 4 weeks |
| STAGE | DOSE | WHEN |
| Starting dose | 18.75 mg once daily | At the start |
| Maximum dose | 15 mg once daily | If needed |
| Dose changes | 3 increases | As tolerated |
Zepbound
| STAGE | DOSE | WHEN |
| Starting dose | 2.5 mg once weekly | Weeks 1-4 |
| Maximum dose | 15 mg once weekly | Week 21 onward |
| Dose changes | 5 increases | Every 4 weeks |
Adipex
| STAGE | DOSE | WHEN |
| Starting dose | 18.75 mg once daily | At the start |
| Maximum dose | 15 mg once daily | If needed |
| Dose changes | 3 increases | As tolerated |
Zepbound vs. Adipex Indications
Zepbound
Zepbound is approved for long-term weight management in adults with obesity, or with overweight plus a weight-related condition like high blood pressure or type 2 diabetes. It is also approved to treat moderate-to-severe obstructive sleep apnea in adults with obesity. It is meant to be used alongside a reduced-calorie diet and increased physical activity, ongoing rather than for just a few weeks.
Chronic weight management in adults with obesity
Weight management with overweight plus a related condition
Moderate-to-severe obstructive sleep apnea with obesity
Used long-term alongside diet and exercise
Adipex
Adipex is approved only as a short-term aid, a few weeks, for weight loss in people with obesity who are also following a reduced-calorie diet and exercise plan. It is not approved for long-term or chronic weight management. Any use beyond the labeled short-term window is off-label.
Short-term (a few weeks) weight loss adjunct
Used with diet, exercise, and behavior changes
Not approved for long-term weight management
Not approved for patients 16 and younger
Zepbound vs. Adipex Pros and Cons
Zepbound
Zepbound has shown substantial weight loss in clinical trials and is approved for ongoing, chronic use rather than a short course. Insurance coverage is inconsistent and many patients pay out of pocket.
Pros
Approved for long-term, chronic weight management
Also approved to treat obstructive sleep apnea
Strong weight loss results in clinical trials
Not a controlled substance
Cons
Roughly $1,050 to $1,100 per month without insurance
Requires a weekly self-injection
Gastrointestinal side effects can be significant during dose increases
Carries a boxed warning for thyroid C-cell tumors
Adipex
Adipex has decades of clinical use and a low cost, but its approval is limited to short-term treatment and it carries abuse potential as a controlled substance. It is not an option for people with cardiovascular disease or uncontrolled high blood pressure.
Pros
Roughly $50 to $150 per month, far less than Zepbound
Taken as a pill, no injections needed
Long track record of use since 1959
Generic phentermine widely available
Cons
Only approved for short-term use, a few weeks
Schedule IV controlled substance with abuse potential
Contraindicated with heart disease or uncontrolled hypertension
Cannot be combined with MAOIs due to hypertensive crisis risk
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