Mephentermine is a

cardiac stimulant A cardiac stimulant is a substance which acts as a stimulant of the heart – e.g., via positive chronotropic or inotropic An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the fo ...

. It has been used as a treatment for

low blood pressure Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the di ...

. Mephentermine belongs to the class of adrenergic and dopaminergic cardiac stimulants excluding

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

s. Used in the treatment of

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, ...

Mechanism of action

Mephentermine appears to act by indirect stimulation of β-adrenergic receptors causing the release of

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad ...

from its storage sites. It has a positive

inotropic An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction. The term ''inotro ...

effect on the

myocardium Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

. AV conduction and refractory period of

AV node The atrioventricular node or AV node electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the lower back section of t ...

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.

Caution

Contraindications

Low blood pressure caused by phenothiazines,

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

, and

pheochromocytoma Pheochromocytoma (PHEO or PCC) is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred t ...

Special Precautions

Patients receiving

monoamine oxidase inhibitor Monoamine oxidase inhibitors (MAOIs) are a class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressants, esp ...

s. For shock due to loss of blood or fluid, give fluid replacement therapy primarily, cardiovascular disease, hypertension,

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

, chronic illnesses, lactation, pregnancy, skin dryness. headache.

Adverse Drug Reactions

The most common side effects are drowsiness, incoherence, hallucinations, convulsions, slow heart rate (

reflex bradycardia Reflex bradycardia is a bradycardia (decrease in heart rate) in response to the baroreceptor reflex, one of the body's homeostatic mechanisms for preventing abnormal increases in blood pressure. In the presence of high mean arterial pressure, the ...

). Fear, anxiety, restlessness, tremor, insomnia, confusion, irritability, and psychosis. Nausea, vomiting, reduced appetite, urinary retention, dyspnea, weakness, neck pain Potentially fatal reactions are due to atrioventricular block, central nervous system stimulation, cerebral hemorrhage, pulmonary edema, and ventricular arrhythmias.

Drug Interactions

Mephentermine antagonizes effect of agents that lower blood pressure. Severe hypertension may occur with monoamine oxidase inhibitors and possibly

tricyclic antidepressant Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and wer ...

s. Additive vasoconstricting effects occur with

ergot Ergot ( ) or ergot fungi refers to a group of fungi of the genus ''Claviceps''. The most prominent member of this group is '' Claviceps purpurea'' ("rye ergot fungus"). This fungus grows on rye and related plants, and produces alkaloids that c ...

alkaloids, and

oxytocin Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytoc ...

. Potentially fatal drug interactions are the risk of abnormal heart rhythm in people undergoing anesthesia with

cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself i ...

and halothane.

References

Substituted amphetamines Alpha-adrenergic agonists Cardiac stimulants Norepinephrine releasing agents Decongestants Carbonic anhydrase activators {{cardiovascular-drug-stub