|Metabolism||Rapidly demethylated in the body followed by hydroxylation.|
|Excretion||Via urine (as unchanged and metabolites); more rapid in acidic urine.|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||163.259 g/mol g·mol−1|
|3D model (JSmol)|
|(what is this?)|
Mephentermine is a cardiac stimulant. It was formerly used in Wyamine nasal decongestant inhalers and before that as a stimulant in psychiatry.
Mechanism of action
Mephentermine appears to act by indirect stimulation of β-adrenergic receptors causing the release of norepinephrine from its storage sites. It has a positive inotropic effect on the myocardium. AV conduction and refractory period of AV node is shortened with an increase in ventricular conduction velocity. It dilates arteries and arterioles in the skeletal muscle and mesenteric vascular beds, leading to an increase in venous return.
Its onset is 5 to–15 minutes with intramuscular dosing, and immediate with intravenous dosing.
Its duration of action is four hours with intramuscular dosing and 30 minutes with intravenous dosing.
Indication and dosage
For maintenance of blood pressure in hypotensive states, the dose for adults is 30–45 mg as a single dose, repeated as necessary or followed by intravenous infusion of 0.1% mephentermine in 5% dextrose, with the rate and duration of administration depending on the patient's response.
For hypotension secondary to spinal anaesthesia in obstetric patients, the dose for adults is 15 mg as a single dose, repeated if needed. The maximum dose 30 mg.
Patients receiving monoamine oxidase inhibitors. For shock due to loss of blood or fluid, give fluid replacement therapy primarily, cardiovascular disease, hypertension, hyperthyroidism, chronic illnesses, lactation, pregnancy.
Adverse Drug Reactions
The most common side effects are drowsiness, incoherence, hallucinations, convulsions, slow heart rate (reflex bradycardia). Fear, anxiety, restlessness, tremor, insomnia, confusion, irritability, and psychosis. Nausea, vomiting, reduced appetite, urinary retention, dyspnea, weakness.
Potentially fatal reactions are due to atrioventricular block, central nervous system stimulation, cerebral hemorrhage, pulmonary edema, and ventricular arrhythmias.
Mephentermine antagonizes effect of agents that lower blood pressure. Severe hypertension may occur with monoamine oxidase inhibitors and possibly tricyclic antidepressants. Additive vasoconstricting effects occur with ergot alkaloids, and oxytocin.
- Whittington RM (May 1963). "Mephentermine Sulphate as a Hypertensive Agent in General Practice". Journal of the Royal College of General Practitioners. 6 (2): 336–7. PMC 1878111. PMID 14000433.
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