Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions contraindicatios, dosages, routes of administration, and any antidotal management for the various cholinergic antagonists (blockers)
Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions contraindicatios, dosages, routes of administration, and any antidotal management for the various cholinergic antagonists (blockers)
Cholinergic antagonist agents bind to muscarinic or nicotinic receptors and prevent the effect of a cholinergic agonist. Cholinergic antagonists are also known as parasympatholytic or anticholinergics. These agents oppose the effect of acetylcholine. Atropine is a widely used cholinergic antagonist.
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CHARACTERISTICS |
ANTIMUSCARINIC AGENY (Atropin, Ipratropium) |
GANGLIONIC BLOCKERS (Nicotine, Mecamylamine) |
NEUROMUSCULAR BLOCKERS (Doxacurium, Vecuronium, Rocuronium, Tubocurarine) |
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MECHANISM OF ACTION |
It blocks nonselective muscarinic receptors. |
These drugs compete with acetylcholine to bind with nicotine receptors |
These drugs block cholinergic transmission by preventing the binding of acetylcholine to its receptor. |
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THERAPEUTIC EFFECT & INDICATION |
Bradycardia, cycloplegia, mydriasis. |
Hypertensive emergencies |
Anesthesia, increase muscle relaxation, psychiatric disorder, orthopedic procedure |
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ADVERSE &TOXIC EFFECT |
Dry mouth, tachycardia, hallucination and delirium, inhibition of sweating, blurring of vision |
Constipation, urinary retention, tachycardia, vasodilation |
Decrease tone and motility in GI tract, arrhythmias, bronchoconstriction |
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DRUG INTERACTION |
Phenothiazine decreases the effectiveness of the drug, MAOIs, antihistamines, and parkinsonism causes increase the effect of anticholinergic |
Catecholamine uptake inhibitor reduces the uptake by norepinephrine |
Aminoglycoside antibodies inhibit the release of acetylcholine, calcium channel blocker increases the activity of neuromuscular blockers |
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CAUSTION & CONTRAINDICATION |
Hypersensitivity, glaucoma, pregnancy, paralytic ileus, intestinal atony, GI obstruction |
Hypersensitivity, pregnancy, lactation |
Increase intracranial pressure and intraabdominal pressure, status asthmatics |
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DOSAGE |
1 mg/ml intravenous |
2.5 mg orally |
1- 1.5 mg/ Kg intravenous, 3-4 mg/Kg intramuscular |
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ROUTES OF ADMINISTRATION |
Topical, subcutaneous, intramuscular, intravenous |
Intravenous, orally |
Intravenous and intramuscular |
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ANTIDOTE |
Physostigmine salicylate |
Trimethaphan mesylate |
Neostigmine, glycopyrrolate. |
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