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. |
| Molecular Weight | 250.3 |
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 | Avoid use in first trimester due to potential vasoconstriction and reduced uterine blood flow. |
| 2nd trimester | Use only if clearly needed; may reduce placental perfusion. |
| 3rd trimester | Avoid near term; may cause neonatal tachycardia or hypertension. |
Clinical note
Comprehensive clinical and safety monograph for WYAMINE SULFATE (WYAMINE SULFATE).
| Placental transfer | Crosses placenta via passive diffusion; evidenced by fetal heart rate changes after maternal administration. |
| Breastfeeding | Excretion in breast milk is unknown; use with caution due to potential for cardiovascular effects in the infant. |
| Lactation Rating |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to mephentermine or sulfitesUncontrolled hypertensionHyperthyroidismNarrow-angle glaucomaConcurrent MAO inhibitor therapy
| 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. |
| Food/Dietary | Avoid tyramine-rich foods (aged cheese, cured meats, fermented products) due to risk of hypertensive crisis, especially if taking MAOIs. Caffeine may increase cardiovascular effects. |
Loading safety data…
| L3 (Moderately Safe) |
| 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. |
| 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. |
| Clinical Pearls | Wyamine Sulfate (mephentermine) is a direct-acting sympathomimetic used for hypotension. Monitor for tachyphylaxis with repeated doses. Use with caution in patients with hyperthyroidism, hypertension, or concurrent MAOIs due to risk of hypertensive crisis. Administer slowly IV to avoid severe hypertension and arrhythmias. |
| Patient Advice | This medication is used to treat low blood pressure. · Report symptoms of chest pain, headache, or palpitations immediately. · Avoid sudden position changes to prevent dizziness. · Do not stop taking this medication abruptly without consulting your doctor. |