Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Adrenergic and Dopaminergic Agent.
ATC Code: R03CA02.
Ephedrine is a sympathomimetic amine acting directly on the alpha and beta receptors and indirectly by increasing the release of noradrenaline by the sympathetic nerve endings. As with any sympathomimetic agent, ephedrine stimulates the central nervous system, the cardiovascular system, the respiratory system, and the sphincters of the digestive and urinary systems. Ephedrine can provoke an increase of glycemia. After intravenous injection of a dose between 10 and 25 mg, the cardiac effects persist for 1 hour.

Pharmacokinetic Properties

5.2 Pharmacokinetic properties
Absorption
Ephedrine is rapidly and completely absorbed after oral, intramuscular or subcutaneous administration.
Ephedrine hydrochloride circulates freely in the plasma.

Distribution
Although specific information is lacking, ephedrine is presumed to cross the placenta and to distribute into milk.
After injection, it is rapidly distributed in the body and accumulates in the liver, kidneys, lungs, spleen and brain. This accumulation results in high distribution volumes ranging between 122 and 320 liters.
Biotransformation
A small fraction of ephedrine is slowly metabolized in the liver by oxidative deamination, demethylation, aromatic hydroxylation, and conjugation. The metabolites are identified as p- hydroxyephedrine, p-hydroxynorephedrine, norephedrine, and conjugates of these compounds.

Elimination
Excretion depends on urine pH:
From 73 to 99% (mean: 88%) in acidic urine.
From 22 to 35% (mean: 27%) in alkaline urine.
After oral or parenteral administration, 77% of ephedrine is excreted in unchanged form in the urine.
The half life depends on urine pH. In acidic urine at pH = 5, the half-life is 3 hours; in alkaline urine at pH = 6.3, the half life is approximately 6 hours.