Chapter 22: Cholinergic-Blocking Drugs – Anticholinergic Effects

Chapter 22 details the class of medications known as cholinergic-blocking drugs, which are also termed anticholinergics, parasympatholytics, or antimuscarinic drugs because they inhibit the actions of acetylcholine (ACh) by competitively binding to muscarinic receptors within the parasympathetic nervous system. This blockade allows the sympathetic (adrenergic) nervous system to dominate, producing effects generally opposite to those caused by cholinergic stimulation. These drugs, historically derived from natural plant alkaloids like atropine and scopolamine, are widely used therapeutically. Indications include cardiovascular management, such as accelerating heart rate to treat symptomatic bradycardia, and respiratory applications like bronchodilation and reduction of excessive secretions for conditions such as asthma, COPD, or preoperatively. They decrease gastrointestinal motility and glandular secretions, making them effective for irritable bowel conditions and hypersecretory states. Additionally, agents like oxybutynin and tolterodine are crucial for managing genitourinary disorders, specifically overactive bladder, by relaxing the detrusor muscle. A narrow therapeutic index means dosage is critical, and overdose can lead to severe central nervous system (CNS) effects, including delirium, hallucinations, and cardiac dysrhythmias. Nursing management focuses heavily on mitigating common adverse effects—including dry mouth (xerostomia), constipation, urinary retention, and blurred vision—and educating patients, especially older adults, about the danger of hyperthermia due to the suppression of sweating. Contraindications such as angle-closure glaucoma and benign prostatic hyperplasia must be carefully assessed prior to administration.