Chapter 20: Cholinergic Drugs

Cholinergic drugs function as parasympathomimetic agents that enhance parasympathetic nervous system activity by replicating acetylcholine effects at various receptor sites throughout the body. The chapter distinguishes between two primary receptor types: nicotinic receptors, which mediate skeletal muscle contraction and ganglionic transmission, and muscarinic receptors, which regulate organ system responses including cardiac, pulmonary, and gastrointestinal functions. Direct-acting cholinergic agonists such as bethanechol, pilocarpine, cevimeline, and succinylcholine bind directly to acetylcholine receptors to produce rapid therapeutic effects, while indirect-acting agents including donepezil, galantamine, rivastigmine, neostigmine, physostigmine, pyridostigmine, and edrophonium work by inhibiting cholinesterase enzymes, thereby prolonging acetylcholine availability in synaptic spaces. Characteristic physiologic responses encompass pupil constriction, salivary gland stimulation, enhanced gastric motility, improved urinary bladder contraction, slowed heart rate, blood vessel dilation, and airway constriction. Clinical applications span diverse conditions including urinary retention management, intraocular pressure reduction in glaucoma, xerostomia relief in Sjögren's syndrome, neuromuscular junction restoration in myasthenia gravis, cognitive symptom mitigation in Alzheimer's disease, and emergency reversal of neuromuscular blocking agents or anticholinergic toxicity. The cholinergic crisis represents the most serious toxicity concern, characterized by the mnemonic SLUDGE reflecting salivation, lacrimation, urinary incontinence, defecation, gastrointestinal cramping, and emesis, alongside additional manifestations including cardiovascular collapse, seizure activity, and respiratory failure. Atropine and epinephrine serve as critical antidotes in acute overdose scenarios. Nursing practice requires comprehensive baseline cardiovascular and respiratory assessment, meticulous dose titration, patient adherence counseling particularly regarding myasthenia gravis medication timing, fall prevention strategies due to orthostatic hypotension risks, and realistic outcome communication regarding Alzheimer's disease management limitations and caregiver support needs.