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Drugs Affecting the Autonomic Nervous System

Drugs Affecting the Autonomic Nervous System. Cholinergic Agents and Cholinergic Blocking Agents. Cholinergic Agents. Drugs that stimulate the parasympathetic nervous system (PSNS) The PSNS is the opposing system to the SNS. Cholinergic Agents. Also known as cholinergic agonists or

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Drugs Affecting the Autonomic Nervous System

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  1. Drugs Affecting the Autonomic Nervous System Cholinergic Agents andCholinergic Blocking Agents

  2. Cholinergic Agents • Drugs that stimulate theparasympathetic nervous system (PSNS) • The PSNS is the opposing system to the SNS

  3. Cholinergic Agents Also known as • cholinergic agonists or • parasympathomimetics

  4. The Parasympathetic and Sympathetic Nervous Systems and Their Relationships to One Another

  5. Cholinergic Agents • Mimic the effects of the PSNS neurotransmitter • Acetylcholine (ACh)

  6. Cholinergic Receptors Two types, determined by: • Location • Action once stimulated Nicotinic receptors and Muscarinic receptors

  7. Nicotinic Receptors • Located in the ganglia of both the PSNS and SNS • Named “nicotinic” because can be stimulated by the alkaloid nicotine

  8. Muscarinic Receptors • Located postsynaptically: • Smooth muscle • Cardiac muscle • Glands of parasympathetic fibers • Effector organs of cholinergic sympathetic fibers • Named “muscarinic” because can be stimulated by the alkaloid muscarine

  9. The Sympathetic, Parasympathetic, and Somatic Nervous Systems

  10. Indirect-Acting Cholinergic Agents (Cholinesterase Inhibitors) • 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

  11. Drug Effects of Cholinergic Agents • Effects seen when the PSNS is stimulated. • The PSNS is the “rest and digest” system.

  12. Drug Effects of Cholinergic Agents “SLUDGE” • Salivation • Lacrimation • Urinary incontinence • Diarrhea • Gastrointestinal cramps • Emesis

  13. Drug Effects of Cholinergic Agents • Stimulate intestine and bladder • Increased gastric secretions • Increased gastrointestinal motility • Increased urinary frequency • Stimulate pupil • Constriction (miosis) • Reduced intraocular pressure • Increased salivation and sweating

  14. Drug Effects of Cholinergic Agents • Cardiovascular effects • Decreased heart rate • Vasodilation • Respiratory effects • Bronchial constriction, narrowed airways

  15. Drug Effects of Cholinergic Agents • At recommended doses, the cholinergics primarily affect the MUSCARINIC receptors. • At high doses, cholinergics stimulate the NICOTINIC receptors.

  16. Drug Effects of Cholinergic Agents • DESIRED EFFECTS: from muscarinic receptor stimulation • Many undesirable effects are due to stimulation of the nicotinic receptors

  17. Cholinergic Agents: Therapeutic Uses Direct-Acting Agents • Reduce intraocular pressure • Useful for glaucoma and intraocular surgery Examples: acetylcholine, carbachol, pilocarpine Topical application due to poor oral absorption

  18. Cholinergic Agents: Therapeutic Uses Direct-Acting Agent—bethanechol • Increases tone and motility of bladder and GI tract • Relaxes sphincters in bladder and GI tract, allowing them to empty • Helpful for postsurgical atony of the bladder and GI tract Oral dose or SC injection

  19. Cholinergic Agents: Therapeutic Uses Indirect-Acting Agents • Cause skeletal muscle contractions • Used for diagnosis and treatment of myasthenia gravis • Used to reverse neuromuscular blocking agents • Used to reverse anticholinergic poisoning (antidote) Examples: physostigmine, pyridostigmine

  20. Cholinergic Agents: Therapeutic Uses Indirect-Acting Agent—donepezil (Aricept) • Used in the treatment of mild to moderate Alzheimer’s disease. • Helps to increase or maintain memory and learning capabilities.

  21. Cholinergic Agents: Side Effects Side 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

  22. Cholinergic Agents: Side Effects Side effects are a result of overstimulation of the PSNS. • Respiratory: • Increased bronchial secretions, bronchospasms • Other: • Lacrimation, sweating, salivation, loss of binocular accommodation, miosis

  23. Cholinergic Agents: Interactions • Anticholinergics, antihistamines, sympathomimetics • Antagonize cholinergic agents, resulting in decreased responses

  24. Cholinergic Agents: Nursing Implications • Keep in mind that these agents will stimulate the PSNS and mimic the action of ACh. • Assess for allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease, or coronary artery disease. • Perform baseline assessment of VS and systems overview.

  25. Cholinergic Agents: Nursing Implications • 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. Patients should not adjust the dosages unless directed by the physician.

  26. Cholinergic Agents: Nursing Implications • Encourage patients with myasthenia gravis to take medication 30 minutes before eating to help improve chewing and swallowing. • When donepezil is prescribed for Alzheimer’s disease, be honest with caregivers and patients that the drug is for management of symptoms, not for a cure. • Therapeutic effects of donepezil may not occur for up to 6 weeks.

  27. Cholinergic Agents: Nursing Implications • Atropine is the antidote for cholinergics. It should be available in the patient’s room for immediate use if needed. • Patients should notify their physician if they experience muscle weakness, abdominal cramps, diarrhea, or difficulty breathing.

  28. Cholinergic Agents: Nursing Implications Monitor for side effects, including: Increased respiratory Abdominal crampingsecretions Bronchospasms Dysrhythmias Difficulty breathing Hypotension Nausea and vomiting Bradycardia Diarrhea Increased sweating Increase in frequency andurgency of voiding patterns

  29. Cholinergic Agents: Nursing 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 bethanecol administration

  30. Cholinergic Blocking Agents • Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)

  31. Cholinergic Blocking Agents: Mechanism of Action • Competitive antagonists • Compete with ACh • Block ACh at the muscarinic receptors in the PSNS • As a result, ACh is unable to bind to thereceptor site and cause a cholinergic effect.

  32. Cholinergic Blocking Agents: Mechanism of Action • Once these drugs bind to receptors, they inhibit nerve transmission at these receptors.

  33. Site of Action of Cholinergic Blockers Within the PSNS

  34. Cholinergic Blocking Agents: Chemical Class Natural Synthetic/Semisynthetic atropine anisotropine clidinium belladonna dicyclomine glycopyrrolate hyoscyamine hexocyclium homatropine scopolamine ipratropium isopropamide oxybutynin propantheline tolterodine tridihexethyl

  35. Drug Effects of Cholinergic Blocking Agents • Cardiovascular • Small doses: decrease heart rate • Large doses: increase heart rate • CNS • Small doses: decrease muscle rigidity and tremors • Large doses: drowsiness, disorientation, hallucinations

  36. Drug Effects of Cholinergic Blocking Agents • Eye • Dilated pupils (mydriasis) • Decreased accommodation due to paralysis of ciliary muscles (cycloplegia) • Gastrointestinal • Relax smooth muscle tone of GI tract • Decrease intestinal and gastric secretions • Decrease motility and peristalsis

  37. Drug Effects of Cholinergic Blocking Agents • Genitourinary • Relaxed detrusor muscle • Increased constriction of internal sphincter • Result: urinary retention • Glandular • Decreased bronchial secretions, salivation, sweating • Respiratory • Decreased bronchial secretions • Dilated bronchial airways

  38. Cholinergic Blocking Agents: Therapeutic Uses CNS Decreased muscle rigidity and muscle tremors • Parkinson’s disease • Drug-induced extrapyramidal reactions

  39. Cholinergic Blocking Agents: Therapeutic Uses Cardiovascular Affect the heart’s conduction system • Low doses: slow the heart rate • High doses: block inhibitory vagal effects on the SA and AV node pacemaker cells • Result: increased heart rate

  40. Cholinergic Blocking Agents: Therapeutic Uses Atropine Used primarily for cardiovascular disorders • Sinus node dysfunction • Symptomatic second-degree heart block • Sinus bradycardia with hemodynamic compromise (advanced life support)

  41. Cholinergic Blocking Agents: Therapeutic Uses Respiratory Blocking the cholinergic stimulation of the PSNS allows unopposed action of the SNS. • Results: • Decreased secretions from nose, mouth, pharynx, bronchi • Relaxed smooth muscles in bronchi and bronchioles • Decreased airway resistance • Bronchodilation

  42. Cholinergic Blocking Agents: Therapeutic Uses Respiratory agents are used to treat: • Exercise-induced bronchospasms • Chronic bronchitis • Asthma • Chronic obstructive pulmonary disease

  43. Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal PSNS controls gastric secretions and smooth muscles that produce gastric motility. • Blockade of PSNS results in: • Decreased secretions • Relaxation of smooth muscle • Decreased GI motility and peristalsis

  44. Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal agents are used to treat: • Peptic ulcer disease • Irritable bowel disease • GI hypersecretory states

  45. Cholinergic Blocking Agents: Therapeutic Uses Genitourinary • Relaxed detrusor muscles of the bladder • Increased constriction of the internal sphincter • Reflex neurogenic bladder • Incontinence

  46. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Cardiovascular Increased heart rate, dysrhythmias CNS CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium

  47. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Eye Dilated pupils, decreased visual accommodation, increased intraocular pressure Gastrointestinal Decreased salivation, decreased gastric secretions, decreased motility

  48. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Genitourinary Urinary retention Glandular Decreased sweating Respiratory Decreased bronchial secretions

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