indication

Used to maintain blood pressure in hypotensive states.

pharmacology

Mephentermine is a sympathomimetic agent with mainly indirect effects on adrenergic receptors. It is used to maintain blood pressure in hypotensive states, for example, following spinal anesthesia. Although the central stimulant effects of mephentermine are much less than those of amphetamine, its use may lead to amphetamine-type dependence. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1248)

mechanism of action

Mephentermine is an alpha adrenergic receptor agonist, but also acts indirectly by releasing endogenous norepinephrine. Cardiac output and systolic and diastolic pressures are usually increased. A change in heart rate is variable, depending on the degree of vagal tone. Sometimes the net vascular effect may be vasodilation. Large doses may depress the myocardium or produce central nervous system (CNS) effects.

biotransformation

Hepatic, by N-demethylation and then p-hydroxylation.

half life

17 to 18 hours.

drug interactions

Amitriptyline: The tricyclic antidepressant, amitriptyline, increases the sympathomimetic effect of mephentermine.

Amoxapine: The tricyclic antidepressant, amoxapine, increases the sympathomimetic effect of mephentermine.

Clomipramine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of mephentermine.

Desipramine: The tricyclic antidepressant, desipramine, increases the sympathomimetic effect of mephentermine.

Doxepin: The tricyclic antidepressant, doxepin, increases the sympathomimetic effect of mephentermine.

Imipramine: The tricyclic antidepressant, imipramine, increases the sympathomimetic effect of mephentermine.

Isocarboxazid: Increased arterial pressure

Linezolid: Possible increase of arterial pressure

Methyldopa: Increased arterial pressure

Midodrine: Increased arterial pressure

Moclobemide: Moclobemide increases the sympathomimetic effect of mephentermine.

Nortriptyline: The tricyclic antidepressant, nortriptyline, increases the sympathomimetic effect of mephentermine.

Phenelzine: Increased arterial pressure

Rasagiline: Increased arterial pressure

Reserpine: Increased arterial pressure

Tranylcypromine: The MAO inhibitor, Tranylcypromine, may increase the vasopressor effect of the alpha1-agonist, Mephentermine. Concomitant therapy should be avoided.

Trimipramine: Trimipramine may increase the vasopressor effect of the alpha1-agonist, Mephentermine. Avoid combination if possible. Monitor sympathetic response to therapy if used concomitantly.