Gastric secretions agents that reduce

Mechanism of Action A G1 ant ispasmodic and ant ichol inergic agent that inhibits the action of acetylcholine at postganglionic (muscarinic) receptor sites. Therapeutic Effect Decreases secretions (bronchial, salivary, sweat gland) and gastric juices and reduces motility of G1 and urinary tract. 

Mechanism of Action A peripheral anticholinergic agent that has limited ability to cross the blood-brain barrier and provides a peripheral blockade of muscarinic receptors. Therapeutic Effect Reduces the volume and the total acid content of gastric secretions, inhibits salivation, and reduces gastrointestinal motility. 

Methantheline and propantheline are synthetic derivatives that, besides their antimuscarinic effects, are ganglionic blocking agents and block the skeletal neuromuscular junction. Propantheline and oxyphenonium reduce gastric secretion, whereas pirenzepine, in addition to reducing gastric secretion, also reduces gastric motility. 

Anticholinergic drugs are only really suitable in the case of agents that show some gastric-selectivity, e.g. pirenzepine and telenzepine (see MUSCARINIC CHOLINOCEPTOR antagonists). They work by reducing the secretion of peptic acid by the stomach mucosa. 

Nonselective antimuscarinic drugs have been employed in the therapy of peptic ulcers (see Chapter 40) because they can reduce gastric acid secretion they also have been used as adjunctive therapy in the treatment of irritable bowel syndrome. Antimuscarinic drugs can decrease the pain associated with postprandial spasm of intestinal smooth muscle by blocking contractile responses to ACh. Some of the agents used for this disorder have only antimuscarinic activity (e.g., propantheline), while other drugs have additional properties that contribute to their antispasmodic action. Dicyclomine (Bentyl) and oxybutynin (Ditropan) at therapeutic concentrations primarily have a direct smooth muscle relaxant effect with little antimuscarinic action. 

The application of R. leads to a reduction in the levels of noradrenaline, dopamine, and serotonin in the synapses R. binds irreversibly to the transport system of noradrenaline (NA) so that the re-uptake of NA in the vesicles of the synapses is inhibited. Thus, transmission of stimuli is reduced, the blood pressure decreases with a concomitant central sedation. R. thus acts as a neuroleptic agent. The side effects of an overdose may include diarrhea, elevated secretion of saliva and gastric juices, depression, and Parkinson s disease. R. is suspected of being carcinogenic since in female patients an increased incidence of breast cancer seems to occur. The roots of R. serpentirm have been used in India for centuries as a sedative they also contain yohimbine. The first total synthesis was achieved by Woodward, for stereospecific synthesis, see Lit.. Deserpidine (11-demethoxyreserpine, canescine, recanescine, CsaHjgNjOg, Mr 578.64, cryst., mp. 228-230°C, [a]o-163° (pyridine) is also aRauvo/-fia alkaloid it exists in polymorphic forms and also lowers the blood pressure. 

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