WYAMINE SULFATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for WYAMINE SULFATE (WYAMINE SULFATE).
Wyamine sulfate (mephentermine sulfate) is a sympathomimetic amine that acts primarily by releasing norepinephrine from presynaptic nerve terminals, with direct alpha- and beta-adrenergic receptor agonist activity. It causes vasoconstriction and positive inotropic effects, increasing cardiac output and blood pressure.
| Metabolism | Hepatic metabolism via monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT); partly excreted unchanged in urine. |
| Excretion | Primarily renal; 90% excreted unchanged in urine within 24 hours. Minimal biliary/fecal elimination (<5%). |
| Half-life | Terminal elimination half-life is 6-8 hours in adults with normal renal function (CrCl >90 mL/min). |
| Protein binding | Approximately 20% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 2-4 L/kg; indicates extensive tissue distribution, including central nervous system. |
| Bioavailability | Oral: <10% due to extensive first-pass metabolism. Intramuscular: ~80-90%. Intravenous: 100%. |
| Onset of Action | Intravenous: 1-2 minutes. Intramuscular: 10-20 minutes. Oral: 30-60 minutes. |
| Duration of Action | Intravenous: 15-30 minutes. Intramuscular: 30-60 minutes. Oral: 2-4 hours. Effects may be prolonged with hepatic impairment. |
Intramuscular injection: 15-30 mg as a single dose; may repeat in 10-15 minutes if needed. Maximum total dose: 60 mg.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (GFR <30 mL/min) due to potential accumulation. |
| Liver impairment | No specific dose adjustment provided; contraindicated in severe hepatic impairment (Child-Pugh class C). Use with caution in moderate impairment (Child-Pugh class B). |
| Pediatric use | Intramuscular injection: 0.5 mg/kg as a single dose; may repeat in 10-15 minutes if needed. Maximum single dose: 15 mg for children <6 years; 30 mg for children 6-12 years. |
| Geriatric use | Use lower end of dosing range (15 mg intramuscular) due to increased sensitivity and risk of cardiovascular adverse effects. Monitor blood pressure and heart rate closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for WYAMINE SULFATE (WYAMINE SULFATE).
| Breastfeeding | Excretion into breast milk is unknown. Due to potential for adverse effects in the neonate, including tachycardia and hypertension, the use of mephentermine during breastfeeding is generally not recommended. M/P ratio is not established. |
| Teratogenic Risk | Wyamine sulfate (mephentermine) is a sympathomimetic amine. Data in human pregnancy are limited. In animal studies, high doses have been associated with fetal abnormalities. Use in first trimester should be avoided unless absolutely necessary. Second and third trimester use may cause fetal tachycardia, arrhythmias, and reduced uterine blood flow. Inadvertent intrauterine exposure or use near term may induce neonatal hypertension or tachycardia. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to mephentermine or other sympathomimetics","Severe hypertension","Pheochromocytoma","Angle-closure glaucoma","Concurrent or recent (within 14 days) monoamine oxidase inhibitor (MAOI) therapy","Hypovolemia (should be corrected prior to use)"]
| Precautions | ["May cause hypertension, tachyarrhythmias, and angina in patients with coronary artery disease.","Use with caution in hyperthyroidism, pheochromocytoma, and severe hypertension.","May cause CNS stimulation, anxiety, and tremor.","Extravasation may cause tissue necrosis; administer into a large vein.","Concurrent use with MAO inhibitors may precipitate hypertensive crisis."] |
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| Fetal Monitoring | Continuous maternal heart rate and blood pressure monitoring. Fetal heart rate monitoring should be considered, especially when used near term or in prolonged therapy. Observe for signs of uterine hyperstimulation or decreased placental perfusion. |
| Fertility Effects | No specific data on human fertility. In animal studies, sympathomimetics have shown adverse effects on reproductive parameters, but relevance to humans is unknown. |