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Drugs Affecting the Autonomic Nervous System

Explore the mechanisms of action, effects, and nursing implications of cholinergic drugs, known as parasympathomimetics, including examples, indications, and potential adverse effects.

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Drugs Affecting the Autonomic Nervous System

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  1. Cholinergic Drugs Drugs Affecting the Autonomic Nervous System

  2. Cholinergic Drugs • Describe the cholinergic drug effects on major body systems. • Discuss the nursing process related to the care of patients receiving cholinergic drugs for select problems.

  3. Cholinergic Drugs • Drugs that stimulate theparasympathetic nervous system (PSNS) • opposing system to the SNS • Known as: cholinergic agonists or parasympathomimetics • Mimic the effects of the PSNS neurotransmitter: acetylcholine (Ach) • Two types of Receptors: • determined by: Location & Action once stimulated • Muscarinic receptors – recommended doses with desired effect • Nicotinic receptors – higher doses with undesirable effects

  4. Cholinergic DrugsMechanism of Action • Direct-acting cholinergic agonists • Bind to cholinergic receptors, activating them • Indirect-acting cholinergic agonists • Inhibit the enzyme acetylcholinesterase - preventing, which breaks down ACh - more ACh is available at the receptors • Reversible - Bind to cholinesterase for a period of minutes to hours • Irreversible - Bind to cholinesterase and form a permanent covalent bond • The body must make new cholinesterase to break these bonds

  5. Cholinergic Drugs“rest and digest” system “SLUDGE” • Salivation • Lacrimation • Urinary incontinence • Diarrhea • Gastrointestinal cramps • Emesis

  6. Cholinergic DrugsDrug Effects • Stimulate intestine and bladder • Increased gastric secretions • Increased gastrointestinal motility • Increased urinary frequency • Stimulate pupils • Constriction (miosis) • Reduced intraocular pressure • Increased salivation and sweating • Cardiovascular effects • Decreased heart rate • Vasodilation • Respiratory effects • Bronchial constriction, narrowed airways

  7. Cholinergic DrugsDrugs • Bethanechol (Urecholine) – urinary retention • Cevimeline (Evoxac) – Xerostomia • Memantine (Namenda) – Alzheimer’s dementia • Physostigmine (Antilirium) – reversal of anticholinergic drugs effects • Pyridostigmine (Mestinon) – Myasthenia gravis

  8. Cholinergic DrugsIndications Direct-acting drugs • Reduce intraocular pressure • Topical useful for glaucoma and intraocular surgery • pilocarpine

  9. Cholinergic DrugsIndications Direct-acting drug—bethanechol (Urecholine) • Increases tone and motility of bladder and GI tract • Relaxes sphincters in bladder and GI tract, allowing them to empty • Used to reverse postsurgical atony of the bladder and GI tract • Oral dose or SC injection

  10. Cholinergic DrugsIndications Indirect-acting drugs • Cause skeletal muscle contractions • Used for diagnosis and treatment of myasthenia gravis • Pyridostigmine (Mestinon) – Myasthenia gravis • Used to reverse neuromuscular blocking drugs/anesthesia • Used to reverse anticholinergic poisoning (antidote) • Examples: physostigmine (Antilirium)

  11. Cholinergic DrugsIndications Indirect-acting drugs—cevimeline (Evoxac) • Used to treat xerostomia (dry mouth) resulting from Sjögren’s syndrome

  12. Cholinergic DrugsAdverse Effects Adverse effects are a result of overstimulation of the PSNS • Cardiovascular • Bradycardia, hypotension, conduction abnormalities (AV block and cardiac arrest) • CNS • Headache, dizziness, convulsions • Gastrointestinal • Abdominal cramps, increased secretions, nausea, vomiting • Respiratory • Increased bronchial secretions, bronchospasm • Other • Lacrimation, sweating, salivation, loss of binocular accommodation, miosis

  13. Cholinergic DrugsInteractions • Anticholinergics, antihistamines, sympathomimetics • Antagonize cholinergic drugs, resulting in decreased responses • Other cholinergic drugs • Additive effects

  14. Cholinergic DrugsNursing Implications • Assess for allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease, or coronary artery disease • Perform baseline assessment of vital signs and systems overview • Medications should be taken as ordered and not abruptly stopped • The doses should be spread evenly apart to optimize the effects of the medication • Overdosing can cause life-threatening problems. Only physicians should adjust the dosages

  15. Cholinergic DrugsNursing Implications • Encourage patients with myasthenia gravis to take medication 30 minutes before eating to help improve chewing and swallowing • When cholinergic drugs are prescribed for Alzheimer’s disease, be honest with caregivers and patients that the drugs are for management of symptoms, not a cure • Therapeutic effects of anti-Alzheimer’s drugs may not occur for up to 6 weeks

  16. Cholinergic DrugsNursing Implications Monitor for therapeutic effects • Alleviated signs and symptoms of myasthenia gravis • In postoperative patients with decreased GI peristalsis, look for: • Increased bowel sounds • Passage of flatus • Occurrence of bowel movements • In patients with urinary retention/hypotonic bladder, urination should occur within 60 minutes of bethanechol administration • ALSO monitor for adverse effects

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