Chapter 21: Cholinergic-Blocking Drugs

Cholinergic-blocking drugs, collectively known as anticholinergics, parasympatholytics, or antimuscarinics, function by inhibiting acetylcholine activity at muscarinic receptors throughout the parasympathetic nervous system, thereby permitting sympathetic activity to become dominant. These medications operate through competitive antagonism at receptor sites and produce widespread physiological effects across multiple organ systems. Characteristic effects include elevation of heart rate, reduction of bronchial and salivary secretions, airway dilation, decreased gastrointestinal motility and secretory output, urinary retention, pupillary dilation, ciliary muscle paralysis, and suppressed perspiration. The chapter details numerous clinical applications including management of Parkinson's disease and drug-induced movement disorders, correction of bradycardia, prevention of motion sickness, preoperative secretion reduction, treatment of urinary incontinence and overactive bladder conditions, management of irritable bowel syndrome, and symptomatic relief in chronic obstructive pulmonary disease and asthma. Representative medications span from traditional agents such as atropine, scopolamine, and glycopyrrolate to selective gastrointestinal agents like dicyclomine, urinary-specific medications including oxybutynin and tolterodine, and newer bladder-selective formulations such as solifenacin, darifenacin, and fesoterodine. The chapter emphasizes recognition and management of adverse effects using the classical mnemonic describing toxicity as producing a constellation of symptoms: elevated body temperature and flushed appearance, severe oral dryness, visual disturbances, facial redness, and altered mental status. Additional adverse reactions encompass tachycardia, constipation, delirium, and dangerous hyperthermia. Treatment of toxicity relies primarily on supportive interventions with physostigmine reserved for severe presentations. Drug interactions occur frequently with tricyclic antidepressants, antihistamines, cardiac glycosides, and concurrent anticholinergic medications. Nursing care requires comprehensive assessment identifying absolute contraindications including glaucoma, anatomical obstructions of the gastrointestinal or genitourinary tract, myasthenia gravis, and acute hemodynamic instability. Nursing interventions emphasize monitoring for central nervous system effects particularly in geriatric populations, implementing strategies for managing xerostomia and heat intolerance, promoting bowel regularity, ensuring proper transdermal patch rotation, and advising patients regarding operation of machinery during periods of visual compromise.