Anticholinergic Agents

CHAPTER 33: Anticholinergic Agents

Learning Objectives

  • Upon completion of this chapter, you will be able to:

    1. Define anticholinergic agents.

    2. Discuss the use of anticholinergic agents across the lifespan.

    3. Describe the therapeutic actions, indications, pharmacokinetics, contraindications and cautions, most common adverse effects, and important drug-drug interactions of anticholinergic agents.

    4. Compare and contrast the prototype drug atropine with other anticholinergic agents.

    5. Outline the nursing considerations, including important teaching points, for patients receiving anticholinergic agents.

Key Terms

  • Anticholinergic: Opposes the effects of acetylcholine at acetylcholine receptor sites.

  • Belladonna: A plant that contains atropine; historically used for pupil dilation and still used in herbal medicine.

  • Cycloplegia: Inability of the lens in the eye to accommodate to near vision, causing blurring and inability to see near objects.

  • Mydriasis: Relaxation of the muscles around the pupil, leading to pupil dilation.

  • Parasympatholytic: Preventing parasympathetic effects, blocking the activity of the parasympathetic system.

Drug List

Anticholinergic Agents/Parasympatholytics

  • aclidinium

  • atropine

  • darifenacin

  • dicyclomine

  • fesoterodine

  • flavoxate

  • glycopyrrolate

  • hyoscyamine

  • ipratropium

  • methscopolamine

  • oxybutynin chloride

  • propantheline

  • revefenacin

  • scopolamine

  • solifenacin

  • tiotropium

  • tolterodine

  • trospium

  • umeclidinium

Overview of Anticholinergic Agents

  • Anticholinergic agents block the effects of acetylcholine, corresponding to the parasympathetic nervous system, also referred to as parasympatholytic agents.

  • Historically used for gastrointestinal (GI) ailments; however, they are less common today due to better-targeted therapies.

  • Anticholinergics are used for:

    • Bronchodilation

    • Overactive bladder treatment

  • Atropine is a well-known anticholinergic drug used for multiple indications including symptomatic bradycardia, pupil dilation, and decreasing secretions.

Anticholinergic Agents in Different Populations
Children

  • These drugs can lead to adverse effects such as:

    • Constipation

    • Urinary retention

    • Heat intolerance

    • Confusion

  • Closely monitor and provide supportive measures during administration.

  • Dicyclomine is not recommended for use in children.

Adults

  • Awareness of potential adverse effects is essential.

  • Encourage fluid intake and awareness of heat intolerance.

  • Safety precautions when experiencing dizziness or blurred vision; advise against operating vehicles.

  • Caution should be exercised during pregnancy due to potential fetal effects and should seek alternative feeding methods during breastfeeding if an anticholinergic is used.

Older Adults

  • Increased likelihood of adverse effects.

  • Renal function changes require closer monitoring and potential dosage adjustment.

  • Emphasize hydration and avoidance of extreme temperatures.

  • Higher susceptibility to confusion, hallucinations, and psychotic syndromes when using anticholinergics.

Therapeutic Actions and Indications

  • Anticholinergics work by blocking acetylcholine at muscarinic receptors affecting parasympathetic impulses.

  • Used for various conditions including:

    • Decreasing secretions prior to anesthesia

    • Treating parkinsonism by blocking acetylcholine

    • Restoring heart rate after vagal stimulation during surgery

    • Alleviating bradycardia from hyperactive carotid reflex

    • Preventing motion sickness

    • Relaxing urinary and biliary colic

    • Management of peptic ulcers, rhinorrhea, and bronchospasm associated with COPD

    • Inducing mydriasis or cycloplegia during ocular procedures.

Comparison of Anticholinergic Agents (Table 33.1)

  • Aclidinium: 400 mcg b.i.d. by oral inhalation; long-term COPD maintenance.

  • Atropine: 0.4-3 mg IM/subcutaneous/IV; various indications including bradycardia, secretions reduction.

  • Darifenacin: 7.5-15 mg/d PO; overactive bladder treatment.

  • Dicyclomine: 80-160 mg/d PO; IBS treatment.

  • Fesoterodine: 4-8 mg/d PO; overactive bladder treatment.

  • Flavoxate: 100-200 mg PO t.i.d. to q.i.d.; urinary tract issues.

  • Glycopyrrolate: 0.125-0.25 mg; decreases secretions preoperatively.

  • Hyoscyamine: Varies; used in gut spasms and ulcers.

  • Ipratropium: 2 inhalations t.i.d. or q.i.d.; COPD treatment.

  • Methscopolamine: 2.5 mg 30-min before meals; GI secretions suppression.

  • Oxybutynin chloride: 15 mg (+ formulations); overactive bladder treatment.

  • Propantheline: 15 mg PO 30 min before meals; GI disorders.

  • Scopolamine: 1.5 mg transdermal every 3 days; motion sickness prevention.

  • Solifenacin: 5-10 mg/d PO; overactive bladder treatment.

  • Tiotropium: One inhalation/d; long-term COPD treatment.

  • Tolterodine: 2 mg b.i.d.; overactive bladder.

  • Trospium: Varies; urinary incontinence.

  • Umeclidinium: One inhalation/d; COPD maintenance.

Pharmacokinetics of Anticholinergic Drugs

  • Routes of administration include oral, IV, IM, subcutaneous, and inhalation.

  • Metabolism occurs in the liver; excretion through urine.

  • Dosage adjustments recommended in cases of hepatic or renal impairment.

Contraindications and Cautions

  • Contraindications include:

    • Known allergy to anticholinergics

    • Glaucoma

    • GI issues: paralytic ileus, colitis, obstruction

    • Prostatic hypertrophy and bladder obstruction

    • Myasthenia gravis

Adverse Effects

Common Adverse Effects include:

  • Ocular: Blurred vision, photophobia, cycloplegia.

  • CNS: Weakness, dizziness, confusion.

  • GI: Dry mouth, constipation, nausea.

  • Cardiovascular: Tachycardia.

  • Urinary: Retention and hesitancy.

  • Thermoregulatory: Heat intolerance.

Classifying Anticholinergic Toxicity

  • Clinical diagnosis based on symptoms—first sign is usually tachycardia.

  • Symptoms include:

    • "Red as a beet": Flushing of the skin.

    • "Dry as a bone": Anhidrosis due to decreased sweating.

    • "Hot as a hare": Hyperthermia due to inability to dissipate heat.

    • "Blind as a bat": Nonreactive mydriasis and vision changes.

    • "Mad as a hatter": Hallucinations or delirium.

    • "Full as a flask": Urinary retention due to muscle control blockade.

Treatment for Anticholinergic Toxicity

  • Immediate stabilization of patient (airway, breathing, circulation) is priority.

  • Use of sodium bicarbonate for arrhythmias; benzodiazepines for agitation/seizures may be considered.

  • Consult with a medical toxicologist for treatment options such as physostigmine, with caution.

Clinically Important Drug-Drug Interactions

  • When combined with other anticholinergic medications, increased risk of side effects.

  • Monitor closely; avoid over-the-counter medications unless advised by a healthcare provider.

  • Anticholinergic effects can be exacerbated by herbal therapies.

Prototype Summary: Atropine

  • Indications:

    • Decrease secretions before surgery, treat parkinsonism, restore cardiac rhythm, relieve bradycardia, alleviate gastrointestinal spams, manage ulcers, and act as an antidote for cholinergic overdose.

  • Actions: Competitively blocks acetylcholine at muscarinic receptor sites.

  • Pharmacokinetics: Various routes lead to variable onset and duration; typically metabolized in the liver.

    • Half-life (T1/2): 2.5 hours.

Nursing Considerations for Patients Receiving Anticholinergic Agents

  • Assessment: Conduct thorough evaluations for contraindications and assess vital signs.

    • Evaluate neurologic status for any CNS effects, monitor GI/GU functions, and renal function for drug excretion changes.

  • Interventions: Include patient education on drug effects, proper administration techniques, hydration practices, and monitoring for adverse effects.

  • Evaluation: Monitor patient response to medications and efficacy of comfort measures.

Key Points

  • Anticholinergic agents block the effects of acetylcholine at receptor sites, reflecting parasympathetic system effects.

  • Patients should be continually monitored for adverse effects including dry mouth, hypotonia, tachycardia, urinary retention, and heat intolerance.

Conclusion

Anticholinergic agents can provide significant therapeutic benefits, while also carrying risks that require rigorous monitoring and patient education to ensure safe and effective treatment.