Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1 PHARMACODYNAMIC PROPERTIES
Mechanism of Action
Doxylamine is an H1 receptor antagonist antihistamine belonging to the ethanolamine group. This group characteristically produce pronounced sedative effects with low incidence of gastrointestinal disturbance. The significant sedative properties result from inhibition of histamine N-methyltransferase and blockage of central histaminergic receptors. Antagonism of other CNS receptor sites such as those for serotonin, acetyl choline and alpha-adrenergic stimulation may be involved.
Anticholinergic activity at muscarinic receptors also occurs.

Clinical Trials
No data available

Pharmacokinetic Properties

5.2 PHARMACOKINETIC PROPERTIES
Absorption: The drug is well absorbed from the gastrointestinal tract. Following oral administration of a 25mg dose therapeutic effects start within 15 to 30 minutes and are fully developed within one hour. Peak plasma concentration of 100ng/ml occurs between 2 and 4 hours. The duration of action is 6-8 hours. After 24 hours, the mean plasma level is 21ng/ml.
Distribution: The drug is well absorbed from the gastrointestinal tract and is widely distributed throughout the body
Metabolism: Metabolism occurs in the liver. The major metabolic pathway is N- demethylation to N-desmethyldoxylamine and N, N-didesmethyldoxylamine. N- acetyl conjugates of these metabolites have been identified. The activity of these metabolites is unknown. N-glucuronidation has been identified as a minor metabolic route. Additional metabolic pathways found in animal studies include N-oxidation, aromatic hydroxylation and ether cleavage.
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Excretion: The elimination half- life has been reported at 10.1and 12 hours. It is prolonged in geriatric males at 15.5+ 2.1 hours.