Metabolic medicines

Phentermine

A sympathomimetic appetite suppressant; its short-term single-ingredient label must be distinguished from extended-release combination evidence.

Randomized combination weight-management trial; single-ingredient evidence boundary; checked 2026-10-01

Also known as: Adipex · Lomaira

Phentermine molecular structure — Structure reference · C10H15N

Practical use

Clinical purpose, evidence and review questions

Identify single versus combination treatment: Keep brand, ingredients and formulation with any quoted weight result.
Track more than the scale: Discuss sleep, resting symptoms and clinician-reviewed blood pressure as well as weight.
Bring contraindication context: Include cardiovascular history, thyroid disease, glaucoma, other stimulants and pregnancy considerations.

CONQUER: phentermine plus topiramate

US prescribing information; checked October 1, 2026

Additional product-specific source

Overview

Phentermine affects appetite through sympathomimetic activity. US single-ingredient labeling describes short-term adjunctive obesity treatment in selected patients. Qsymia combines phentermine with topiramate for longer-term weight management; its trial results and precautions belong to that specific combination.

Risks and limitations

Blood-pressure elevation, palpitations, insomnia, agitation, tolerance and dependence concerns matter. Cardiovascular disease, uncontrolled hypertension, hyperthyroidism, glaucoma, pregnancy and certain drug interactions are contraindications. New breathlessness, chest pain, fainting or leg swelling requires prompt assessment.

How to read this

Weight loss is not a direct measure of fat loss, muscle preservation or cardiovascular benefit. A combination trial cannot tell us how much each ingredient would achieve alone.

Research explained

CONQUER: phentermine plus topiramate

Who was studied

2,487 adults aged 18–70 with elevated BMI and at least two weight-related risk factors randomized to placebo or two extended-release combination groups for 56 weeks, alongside lifestyle intervention.

What was found

Mean body-weight change was −1.2% with placebo and −7.8% or −9.8% with the combinations. At least 5% loss occurred in 21%, 62% and 70%, respectively. Dry mouth, tingling, constipation and insomnia were more common with active treatment.

What it cannot establish

The study tested two ingredients together. It does not establish those percentages for phentermine alone, isolate body-fat change or demonstrate fewer cardiovascular events.

Read the original study