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

Most common
nausea (up to 29%)
diarrhea (up to 23%)
constipation (up to 17%)
vomiting (up to 13%)

Adipex

Most common
insomnia (not specified)
dizziness (not specified)
restlessness (not specified)
dry mouth (not specified)

Zepbound vs. Adipex Dosage

Zepbound

Dosage
Dosage Table
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

Dosage
Dosage Table
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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