Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties
Pharmacotherapeutic group: Parasympathomimetics, Choline esters, Bethanechol, ATC-Code: N07AB02.
Mechanism of action
Bethanechol chloride is a parasympathomimetic active substance whose major pharmacologic effects result from direct and selective stimulation of cholinergic receptors of the smooth muscle, especially those of the bladder and the gastrointestinal tract. Bethanechol chloride is a synthetic choline ester, which is chemically and pharmacologically similar to the neurotransmitter acetylcholine. Compared with acetylcholine, bethanechol chloride acts mainly on muscarinic receptors and shows in therapeutic dosage negligible nicotinergic effects as well as a significantly longer effectiveness due to its low sensitivity to cholinesterase.

Pharmacodynamic effects
Bethanechol chloride increases the tonus of the bladder muscle (detrusor) and the vesical pressure and therefore supports spontaneous bladder voiding.
Bethanechol chloride stimulates muscle activity of the gastrointestinal tract and digestive glands. The food passage in the entire digestive tract is accelerated. The increased tonus of the lower oesophageal sphincter prevents reflux of acidic stomach contents. Secretion from the lacrimal, salivary and perspiratory glands is increased. Bronchial constriction and increased bronchial secretion can be observed.

Clinical efficacy and safety
Bethanechol chloride given orally shows only slight cardiovascular effects. In usual therapeutic doses, heart rate, blood pressure and peripheral blood circulation remain unchanged. The function of ganglia and skeletal muscles is not affected.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties

Resorption
Bethanechol chloride is poorly absorbed from the gastrointestinal tract.
Distribution and biotransformation
In therapeutic doses, it does not cross the blood-brain barrier. Its distribution in other compartments, the metabolism and the elimination are not known in detail.

Pharmacokinetic/pharmacodynamic relationship
The effects of bethanechol chloride on the gastrointestinal and the urinary tracts can sometimes be observed after 30 minutes, but usually start 60-90 minutes after administration and last for approximately 1 hour. The effects can last for up to 6 hours if a dose of 300 mg or more is administered.