Phentermine Dosage
Medically reviewed by Drugs.com. Last updated on Jul 27, 2023.
Applies to the following strengths: 30 mg; 15 mg; 37.5 mg; 8 mg; 18.75 mg; resin 15 mg; resin 30 mg
Usual Adult Dose for:
Additional dosage information:
Usual Adult Dose for Obesity
8 mg tablet (Lomira): 8 mg orally 3 times a day 30 minutes before meals
- Some patients may only require 4 mg dose (one-half tablet) 3 times a day
15 and 30 mg capsules: 15 or 30 mg orally approximately 2 hours after breakfast
37.5 mg capsules and tablets (Adipex-P): 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast
- Some patients may only require 18.75 mg (one-half tablet) orally once a day OR 18.75 mg orally twice a day
Comments:
- Dosage should be individualized to obtain an adequate response with the lowest effective dose.
- Late evening dosing should be avoided due to the possibility of insomnia.
Use: Short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction in the management of exogenous obesity in patients with an initial body mass index (BMI) of 30 kg/m2 or greater, or BMI of 27 kg/m2 or greater in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).
Renal Dose Adjustments
Mild to moderate renal impairment: No adjustment recommended
Severe renal impairment (eGFR 15 to 29 mL/min/1.73 m2): Maximum dose: 15 mg/day
ESRD (eGFR less than 15 mL/min/1.73 m2): Avoid use
Liver Dose Adjustments
No adjustment recommended
Dose Adjustments
Elderly: Dose selection should be cautious, usually starting at the low end of the
dosing range; consider monitoring renal function as this drug is substantially excreted by the kidney
Precautions
CONTRAINDICATIONS:
- History of cardiovascular disease (e.g., arrhythmias, congestive heart failure, coronary artery disease, uncontrolled hypertension, stroke)
- Hypersensitivity or idiosyncratic reaction to sympathomimetic drugs
- Hyperthyroidism
- Agitated states
- Glaucoma
- History of drug abuse
- Use of monoamine oxidase inhibitors concurrently, or within 14 days
- Breastfeeding
- Pregnancy
Safety and efficacy have not been established in patients younger than 17 years.
Consult WARNINGS section for additional precautions.
US Controlled Substance: Schedule IV
Dialysis
Not recommended
Other Comments
Administration Advice:
- Take orally; avoid late evening administration due to the possibility of resulting insomnia
General:
- This drug is indicated for short-term use in a weight loss program based on exercise, behavioral modification, and caloric restriction.
- The safety and efficacy of combination therapy with phentermine and any other drug products for weight loss have not been established; coadministration of drug products for weight loss is not recommended.
- Tolerance to anorectant effect generally develops and if this occurs, this drug should be discontinued; the recommended dose should not be exceeded.
Monitoring:
- Monitor for development of tolerance
- Consider monitoring renal function in elderly patients
- Monitor for development of new, unexplained symptoms of dyspnea, angina pectoris, syncope, or lower extremity edema
- Monitor for potential abuse
Patient Advice:
- Patients should be informed about the risks of using this drug, potential adverse reactions, and when to contact their healthcare provider.
- Patients should be instructed to avoid activities that require mental alertness such as driving and operating machinery until they know how this drug affects them.
- Women who are considering becoming pregnant should speak with their healthcare provider; this drug should not be used by women who are pregnant or breastfeeding.
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- Phentermine monograph
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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.