PRELUDIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRELUDIN (PRELUDIN).
PRELUDIN (phenmetrazine) is a sympathomimetic amine that acts as a central nervous system stimulant. Its mechanism involves facilitating the release of norepinephrine and dopamine from presynaptic nerve terminals in the brain, thereby increasing their concentrations in the synaptic cleft and enhancing adrenergic and dopaminergic neurotransmission.
| Metabolism | Phenmetrazine is primarily metabolized in the liver via N-dealkylation and aromatic hydroxylation, with cytochrome P450 (CYP) enzymes involved, notably CYP3A4 and CYP2D6. Metabolites are excreted mainly in urine. |
| Excretion | Primarily renal elimination; approximately 90% of a dose is excreted in urine as unchanged drug and metabolites, with about 10% via feces. |
| Half-life | Terminal elimination half-life ranges from 8 to 12 hours in adults; may be prolonged in elderly or those with renal impairment, requiring dose adjustment. |
| Protein binding | Approximately 80% bound to serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd is 3.0–5.0 L/kg, indicating extensive tissue distribution; reflects high penetration into body tissues including brain. |
| Bioavailability | Oral: 85–90% due to minimal first-pass metabolism; intravenous: 100%; subcutaneous: approximately 90%. |
| Onset of Action | Oral: 15–30 minutes; intravenous: immediate; subcutaneous: 10–20 minutes. |
| Duration of Action | Oral: 4–6 hours; intravenous: 2–4 hours; subcutaneous: 3–5 hours; clinical effect duration is dose-dependent and may vary with individual metabolism. |
25 mg orally three times daily, 1 hour before meals.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR 30-60 mL/min: reduce dose by 50%; GFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: contraindicated. |
| Pediatric use | Not recommended for pediatric use (safety and efficacy not established). |
| Geriatric use | Use with caution; initiate at 12.5 mg twice daily due to increased sensitivity and risk of adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRELUDIN (PRELUDIN).
| Breastfeeding | Preludin is excreted into breast milk; M/P ratio not established. Can cause irritability, poor feeding, and stimulation in the infant. Due to potential for serious adverse effects (including cardiovascular stimulation and growth suppression), breastfeeding is not recommended during use. |
| Teratogenic Risk | Preludin (phenmetrazine) is an anorectic sympathomimetic amine. Human data are limited; animal studies suggest potential for increased risk of fetal abnormalities (e.g., cardiovascular and skeletal malformations) at high doses. Use in first trimester may be associated with a small increased risk of congenital anomalies. Third trimester use can lead to neonatal withdrawal symptoms (e.g., irritability, hypertonia) and potential preterm labor. Overall, teratogenic risk is considered moderate; contraindicated during pregnancy unless benefit clearly justifies risk. |
■ FDA Black Box Warning
WARNING: ABUSE AND DEPENDENCE. Phenmetrazine has a high potential for abuse and may lead to psychological dependence and severe social dysfunction. Administration should be carefully monitored, and the drug should be prescribed only for short-term use.
| Serious Effects |
Hypersensitivity to phenmetrazine or any component of the formulation. Advanced arteriosclerosis. Symptomatic cardiovascular disease (e.g., coronary artery disease, hypertension). Moderate to severe hypertension. Hyperthyroidism. Glaucoma. Agitated states. History of drug abuse. Concomitant use or within 14 days of MAO inhibitors (risk of hypertensive crisis). Lactation.
| Precautions | Cardiovascular events: increased risk of hypertension, tachyarrhythmias, myocardial infarction, and sudden death, especially in patients with pre-existing cardiovascular disease. Psychiatric effects: may exacerbate or precipitate psychosis, mania, or aggression. Seizure risk: may lower seizure threshold. Potential for abuse and dependence. Avoid use in patients with a history of drug abuse. Use with caution in patients with hypertension, hyperthyroidism, glaucoma, or hepatic impairment. |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of CNS stimulation. Fetal monitoring includes assessment of intrauterine growth (ultrasound) due to risk of preterm labor and birth weight reduction. Neonatal monitoring required for withdrawal signs if used near term. |
| Fertility Effects | Preludin may impair fertility in females through anovulatory cycles secondary to weight loss and hormonal alterations. In males, high doses may reduce sperm count or motility. Use for weight loss in women of reproductive potential not recommended. |