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Phentermine / Topiramate Dosage

Medically reviewed on February 16, 2018.

Applies to the following strengths: 3.75 mg-23 mg; 7.5 mg-46 mg; 11.25 mg-69 mg; 15 mg-92 mg

Usual Adult Dose for Weight Loss

-Initial dose: Take one capsule of the lowest dose (phentermine 3.75 mg/topiramate 23 mg extended-release) orally once a day in the morning for the first 14 days.

-Maintenance dose: After 14 days, take one capsule of the recommended dose (phentermine 7.5 mg/topiramate 46 mg extended-release) orally once a day in the morning.

Comments:
-Weight loss should be evaluated after 12 weeks with phentermine 7.5 mg/topiramate 46 mg extended-release. If a patient has not lost at least 3% of baseline body weight, treatment discontinuation or dose escalation should be considered as it is unlikely the patient will achieve and sustain clinically meaningful weight loss at this dose.

Use: Adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in patients with an initial body mass index (BMI) of 30 kg/m2 or greater (obese) OR 27 kg/m2 or greater (overweight) in the presence of at least one weight-related comorbidity such as hypertension, type 2 diabetes mellitus, or dyslipidemia.

Renal Dose Adjustments

-Mild renal impairment (CrCl 50 mL/min or more): No adjustment recommended.
-Moderate renal impairment (CrCl 30 to less than 50 mL/min): Dosing should not exceed phentermine 7.5 mg/topiramate 46 mg extended-release orally once a day in the morning.
-Severe renal impairment (CrCl less than 30 mL/min): Dosing should not exceed phentermine 7.5 mg/topiramate 46 mg extended-release orally once a day in the morning.

Liver Dose Adjustments

-Mild liver impairment (Child-Pugh score 5 to 6): No adjustment recommended.
-Moderate liver impairment (Child-Pugh score 7 to 9): Dosing should not exceed phentermine 7.5 mg/topiramate 46 mg extended-release orally once a day in the morning.
-Severe liver impairment (Child-Pugh score 10 to 15): Data not available; Avoid use per manufacturer.

Dose Adjustments

Evaluate weight loss after 12 weeks of treatment with phentermine 7.5 mg/topiramate 46 mg extended-release:
-If a patient has not lost at least 3% of baseline body weight: Discontinue or escalate the dose to phentermine 11.25 mg/topiramate 69 mg extended-release orally once a day in the morning for 14 days then increase the dose to phentermine 15 mg/topiramate 92 mg extended-release orally once a day in the morning.

Evaluate weight loss after 12 weeks of treatment with phentermine 15 mg/topiramate 92 mg extended-release:
-If a patient has not lost at least 5% of baseline body weight: Discontinue, as it is unlikely the patient will achieve and sustain clinically meaningful weight loss with continued treatment.

How to discontinue treatment:
-To prevent a possible seizure, discontinue treatment gradually by taking a dose every other day for at least 1 week prior to stopping treatment altogether.

Precautions

US REMS: The US FDA requires a Risk Evaluation and Mitigation Strategy (REMS) for this drug. It includes a medication guide, elements to assure safe use, and an implementation system. For additional information: www.fda.gov/REMS.

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.

US Controlled Substance: Schedule IV

Dialysis

End-stage renal disease on dialysis: Data not available; Avoid use per manufacturer.

Other Comments

Administration advice:
-Take with or without food.
-Avoid dosing in the evening to prevent possible insomnia.

General:
-The following doses are for titration purposes only: phentermine 3.75 mg/topiramate 23 mg extended-release and phentermine 11.25 mg/topiramate 69 mg extended-release capsules.
-The effect of this drug on cardiovascular morbidity and mortality has not been established.
-The safety and effectiveness of this drug in combination with other weight loss products, including prescription and over-the-counter drugs and herbal preparations, have not been established.
-This drug is only available through certified pharmacies.

Monitoring:
-Obtain a negative pregnancy test before treatment initiation and monthly thereafter in females of reproductive potential.
-Measure blood pressure prior to and during treatment in patients being treated with antihypertensive medications.
-Measure electrolytes including serum bicarbonate prior to and during treatment.
-Monitor patients for the appearance or worsening of metabolic acidosis if they are concomitantly taking a carbonic anhydrase inhibitor and have a predisposing condition for metabolic acidosis.
-Measure blood glucose levels prior to and during treatment in type 2 diabetic patients.
-Monitor for hypokalemia per standard of care.
-Perform appropriate monitoring in situations where immediate termination of this drug is medically required as abrupt withdrawal of topiramate has been associated with seizures in individuals without a history of seizures or epilepsy.
-Monitor for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.
-Measure serum creatinine levels prior to and during treatment.
-Obtain a blood chemistry profile that includes bicarbonate, creatinine, potassium, and glucose at baseline and periodically during treatment.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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