PHENDIMETRAZINE TARTRATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHENDIMETRAZINE TARTRATE (PHENDIMETRAZINE TARTRATE).
Phendimetrazine is a sympathomimetic amine that acts as an appetite suppressant by stimulating the hypothalamus to release norepinephrine, leading to decreased food intake and increased energy expenditure. It is a prodrug that is metabolized to phenmetrazine, which is a potent central nervous system stimulant with amphetamine-like effects.
| Metabolism | Primarily metabolized in the liver via N-demethylation to its active metabolite, phenmetrazine. Other metabolites include phendimetrazine N-oxide and norphenmetrazine. CYP450 enzymes are involved, though specific isoforms not well characterized. |
| Excretion | Primarily renal (≥70% unchanged) with minor biliary/fecal elimination (<10%) |
| Half-life | Terminal half-life 3-4 hours; clinical context: requires multiple daily dosing |
| Protein binding | 10-15% bound to albumin |
| Volume of Distribution | 2-3 L/kg; indicates extensive tissue distribution |
| Bioavailability | Oral: approximately 80-90% |
| Onset of Action | Oral: 30-60 minutes |
| Duration of Action | 4-6 hours; note: tolerance may develop with prolonged use |
Oral: 35 mg twice daily or three times daily, 1 hour before meals; extended-release: 105 mg once daily in the morning.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in severe renal impairment (GFR < 30 mL/min). No specific dose adjustments for mild-moderate impairment; use with caution. |
| Liver impairment | Not recommended in Child-Pugh class B or C. Use with caution in mild impairment. |
| Pediatric use | Not recommended for children under 12 years; safety and efficacy not established. |
| Geriatric use | Start at lower end of dosing range; monitor for increased sensitivity and cardiovascular effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PHENDIMETRAZINE TARTRATE (PHENDIMETRAZINE TARTRATE).
| Breastfeeding | Excreted in breast milk; M/P ratio unknown. Contraindicated in breastfeeding due to potential CNS stimulation and cardiovascular effects in infant. |
| Teratogenic Risk | First trimester: Limited data; potential for increased risk of oral clefts. Second/third trimester: Anorexiant effects may cause fetal growth restriction; avoid use due to maternal hypertension risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
Phendimetrazine is not approved for use in patients with a history of drug abuse or dependence. It has a high potential for abuse and may lead to dependence. Use caution in patients with cardiovascular disease or hypertension.
| Serious Effects |
Hypersensitivity to phendimetrazine or any component of the formulation, advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension, hyperthyroidism, glaucoma, agitated states, history of drug abuse, during or within 14 days of MAOI therapy
| Precautions | Increased risk of pulmonary hypertension and valvular heart disease; monitor for dyspnea, chest pain, or edema. Tolerance may develop; discontinue if tolerance occurs. May impair ability to perform hazardous tasks. Use with caution in patients with hypertension, diabetes, or glaucoma. Do not use with MAOIs or within 14 days of discontinuation. |
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| Monitor maternal blood pressure and heart rate; fetal growth ultrasound if used during pregnancy. Discontinue if maternal hypertension or fetal distress. |
| Fertility Effects | No known adverse effects on fertility; weight loss may improve ovulatory function in obese women. |