Phentermine
Phentermine is an appetite suppressant used for short-term obesity treatment, acting as a sympathomimetic amine similar to amphetamines to reduce hunger.
Phentermine is an appetite suppressant used for short-term obesity treatment that works by reducing hunger signals in the brain.
Key facts at a glance
- ATC
- A08AA01
- RxNorm
- 8152
- Generic
- Phentermine
- Class
- atc-a08
- Brands
- Qsymia, Lomaira, Adipex-P
- Availability
- rx
- Pregnancy
- X
- Lactation
- unsafe
- Routes
- oral
- Forms
- capsule, tablet
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 15-37.5mg once daily
- Maximum
- consult physician
- Frequency
- once daily (morning)
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- not recommended for patients under 16 years of age
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 15mg once daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
second trimesterdiscontinue use
do not use during second trimester
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesterdiscontinue use
do not use during third trimester
regular fetal monitoring and uterine activity
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingavoid
do not use while breastfeeding - phentermine is excreted in breast milk
monitor infant for irritability and poor feeding
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
adolescents 12 17not recommended
not recommended for patients under 18 years of age
growth and developmental monitoring if used
Use of this medication in this population requires careful consideration of risks and benefits.
geriatric
elderly 65 yearsreduce dose and use lowest effective
use with caution due to increased sensitivity to cardiovascular effects
monitor blood pressure and heart rate closely
Use with caution and monitor for adverse effects.
renal_impairment
moderatereduce dose
use with caution and consider dose reduction in moderate renal impairment
monitor renal function and blood pressure
Use with caution and monitor for adverse effects.
hepatic_impairment
mild to moderatereduce dose
use with caution in hepatic impairment - drug is metabolized by liver
monitor liver function tests
Use with caution and monitor for adverse effects.
Statistics and clinical data
FDA approved since
FDA approval year for phentermine as an appetite suppressant
Drug class
Phentermine is classified as a sympathomimetic anorectic agent
Common uses
Indicated as an appetite suppressant for weight loss in obese or overweight patients
Controlled substance schedule
Phentermine is classified as a Schedule IV controlled substance due to potential for abuse
Phentermine is indicated for short-term weight loss management in individuals with obesity. It is typically prescribed when diet and exercise alone have not been sufficient to achieve desired weight loss goals.
Phentermine acts as an anorectic (appetite suppressant) by stimulating the central nervous system. It is a sympathomimetic amine with pharmacologic activity similar to amphetamines, reducing hunger signals in the brain to decrease food intake.
Phentermine is a controlled substance due to its similarity to amphetamine drugs and carries potential for dependence with prolonged use. It is intended for short-term use only. Common side effects may include increased heart rate, blood pressure elevation, and insomnia. Patients with cardiovascular conditions, hyperthyroidism, or history of substance abuse should use caution or avoid this medication.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy