Anticholinergics action

Research for an antidepressant among non-tricyclic compounds with pharmacological effects qualitatively different from those of the conventional tricyclic compounds led to the preparation and testing of a series of indazole derivatives for reserpine-like activity in mice. l-[3-(Dimethylamino)propyl]-5-methyl-3-phenyl-l//-indazole (FS-32 692) antagonizes reserpine-induced effects and potentiates amphetamine-induced self-stimulation and l-Dopa-induced increase in motor activity. FS-32 produces an anticholinergic action mainly on the central nervous System, while the action of imipramine occurs centrally as well as peripherally (79AF511). 

As discussed, PCP, ditran, and scopolamine exert anticholinergic action. This property apparently is not linked to the hallucinogenic action of these molecules, however, since other hallucinogens, such as LSD and mescaline, do not affect cholinergic systems in doses sufficient to provoke hallucinatory-like behaviors in animals (67). Nevertheless, Revuelta et al. (96) noted a decreased turnover... 

Trihexyphenidyl, an antiparkinsonian drug, possesses central and peripheral anticholinergic actions, as well as a direct relaxant effect on smooth muscle. It reduces muscle rigidity and general stiffness, and has a relatively minor effect on tremors. It is used in Parkinsonism in the form of monotherapy as well as in combination with levodopa. The most common synonyms are parkopan, parkinsan, and cyclodol. 

Over the course of the past few decades, a number of synthetic atropine-like substances with more spasmolytic and less anticholinergic action and causing fewer side effects have been used clinically in treating stomach ulcers, pylorospasms, and hyperperistaltics. 

Cyclizine exhibits antihistamine and anticholinergic action and is used for vomiting and diarrhea. The exact mechanism of action is not known. Synonyms of this drug are marezine and migril. 

Because of the anticholinergic action of these agents, use with caution and with appropriate monitoring in patients with glaucoma, obstructive disease of the Gl or GU tract, and in elderly males with possible prostatic hypertrophy. These drugs may have a hypotensive action, which may be confusing or dangerous in postoperative patients. 

Anticholinergic effects Because of its anticholinergic action, use with caution in patients with a history of urinary retention, angle-closure glaucoma, and increased intraocular pressure. 

Quinidine s effect on the electrical properties of a particular cardiac tissue depends on the extent of parasympathetic innervation, the level of parasympathetic tone, and the dose. The anticholinergic actions of quinidine predominate at lower plasma concentrations. Later, when steady-state therapeutic plasma concentrations have been achieved, the drug s direct electrophysiological actions predominate. The direct and indirect electrophysiological actions are summarized in Table 16.2. 

The indirect effect of qutnidine on the sinoatrial node is a result of the drug s potential to exert an anticholinergic action resulting in a slight increase in heart rate. Higher concentrations of quinidine have a direct effect of depressing the rate of spontaneous diastolic depolarization. 

Disopyramide depresses conduction velocity and increases the ERP of the A-V node through a direct action. Its anticholinergic actions, however, produce an increase in conduction velocity and a decrease in the ERP. The net effect of disopyramide on A-V nodal... 

Because of its anticholinergic properties, disopyramide should not be used in patients with glaucoma. Urinary retention and benign prostatic hypertrophy are also relative contraindications to disopyramide therapy. Patients with myasthenia gravis may have a myasthenic crisis after disopyramide administration as a result of the drug s local anesthetic action at the neuromuscular junction. The elderly patient may exhibit increased sensitivity to the anticholinergic actions of disopyramide. 

The depressant effects of propranolol on the A-V node are more pronounced than are the direct depressant effects of quinidine. This is due to propranolol s dual actions of p-blockade and direct myocardial depression. Propranolol administration results in a decrease in A-V conduction velocity and an increase in the A-V nodal refractory period. Propranolol does not display the anticholinergic actions of quinidine and other antiarrhythmic agents. 

Mechanism of Action An antihistamine and anticholinergicthat competes for H,-receptor sites on effector cells of the G1 tract, blood vessels, and respiratory tract. The anticholinergic action diminishesvestibular stimulation and depresses labyrinthine function. Therapeutic Effect Prevents symptoms of motion sickness. Pharmacokinetics Well absorbed following PO administration. Metabolized in liver. Excreted in urine. Half-life Unknown. 

The most common side effects of the older antidepressants, especially those of the sedative type, are vegetative and mostly due to the anticholinergic action of these products dry mouth, difficulties of visual accommodation, constipation, impotence in men, dizziness, increased sweating and palpitations. Of medical... 

This study, notwithstanding its imperfect design, is often quoted as evidence to show that improvement of depression and normalization of cognitive performance are likely to go together, and that antidepressants with strong anticholinergic action are not really harmful for the cognitive function of depressed patients. 

With regard to its effects on cognitive performance in the target population, the SSRI sertraline appears to be the most thoroughly studied newer antidepressant. Lane and O Hanlon (1999) listed three controlled clinical studies with fluoxetine and three with sertraline however, all three trials with fluoxetine and one of the trials with sertraline were not sufficiently powered to demonstrate reliable differences between treatments. One of the two adequately powered studies, a comparison between nortriptyline and sertraline in elderly depressed patients (Bondareff et al., 2000 see Box 7.3), supports the notion that antidepressants with anticholinergic action (such as nortriptyline) are similarly... 

Many antihistaminics have been added to antitussive/expectorant formulations. They do not act on cough centre but provide relief due to their sedative and anticholinergic action. 

Cyclizine has antimuscarinic properties and is a potent anti-emetic, effective for the control of postoperative and drug-induced nausea and vomiting. It has been used to prevent motion sickness, although diphenhydramine and promethazine are more effective. It is available in oral and parenteral formulations. In contrast to many other first-generation antihistamines sedation is not marked. It is available in tablet form as the hydrochloride and in injectable form as the lactate. Because of its anticholinergic action, blurred vision and dry mouth are associated with clinical doses. When given by rapid intravenous injection tachycardia may be a problem. Meclozine is a related drug which, like cyclizine, is used primarily for motion sickness. 

Gardner, Eliot L., Leslie S. Walker, and William Paredes. 1993. "Clozapine s Functional Mesolimbic Selectivity Is Not Duplicated by the Addition of Anticholinergic Action to Haloperidol A Brain Stimulation Study in the Rat." Psychopharmacology 110 119-24. 

Piperazine (15b) itself, often as its citrate due to its low toxicity and cheapness, is still used for the treatment of pinworm and Ascaris infections. It has been shown to block neuromuscular transmission in Ascaris by means of an anticholinergic action at the... 

In terms of side effects of the tricyclic antidepressants (Table 6—5), blockade of alpha 1 adrenergic receptors causes orthostatic hypotension and dizziness (Fig. 6—30). Anticholinergic actions at muscarinic cholinergic receptors cause dry mouth, blurred vision, urinary retention, and constipation and memory disturbances (Fig. 

The efficacy of imipramine has been repeatedly demonstrated in controlled trials about 85% of children treated within a week of the start of medication, but tolerance frequently develops after a number of weeks and relapse is high after discontinuation of the treatment. Relatively low doses of imipramine only are needed, but the typical side effects of tricyclic antidepressants limit the prolonged use of the drug. The mechanism of action of imipramine in the treatment of nocturnal enuresis is unclear but one possible action is through a direct anticholinergic action on the bladder wall. 

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