Mephentermine
Indications
Mephentermine is used for:
Maintenance of blood pressure in hypotensive states, Hypotension secondary to spinal anaesthesia in obstetric patients
Adult Dose
Intravenous
Maintenance of blood pressure in hypotensive states
Adult: 30-45 mg as a single dose, repeated as necessary or followed by IV infusion of 0.1% mephentermine in 5% dextrose, rate and duration of administration will depend on patient's response.
Hypotension secondary to spinal anaesthesia in obstetric patients
Adult: 15 mg as a single dose, repeat if needed.
Child Dose
Renal Dose
Administration
Contra Indications
Hypotension caused by phenothiazines. Hypertension. Phaeochromocytoma.
Precautions
Patient on MAOIs. For shock due to loss of blood or fluid, give fluid replacement therapy primarily, CVS disease, hypertension, hyperthyroidism, chronic illnesses. Lactation, pregnancy.
Pregnancy-Lactation
Interactions
Antagonises effect of hypotensive agents. Severe hypertension with MAOIs and possibly TCAs. Additive vasoconstricting effects with ergot alkaloids, oxytocin.
Potentially Fatal: Risk of arrhythmia in patients undergoing anesthesia with cyclopropane and halothane.
Adverse Effects
Side effects of Mephentermine :
Drowsiness, incoherence, hallucinations, convulsions, tachycardia. Fear, anxiety, restlessness, tremor, insomnia, confusion, irritability and psychosis. Nausea, vomiting, reduced appetite, urinary retention, dyspnoea, weakness.
Potentially Fatal: AV block, CNS stimulation. Cerebral haemorrhage and pulmonary oedema, ventricular arrhythmias.
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.