Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Chapter 20 Cholinergic Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Cholinergic Drugs Drugs that stimulate the parasympathetic nervous system (PSNS) The PSNS is the opposing system to the sympathetic nervous system (SNS) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Cholinergic Drugs (cont’d) Also known as cholinergic agonists or parasympathomimetics Mimic effects of the PSNS neurotransmitter acetylcholine (ACh) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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Cholinergic Receptors Two types, determined by: Location Action once stimulated Nicotinic receptors Muscarinic receptors Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Nicotinic Receptors Located in the ganglia of both the PSNS and SNS Named nicotinic because they can be stimulated by the alkaloid nicotine Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Muscarinic Receptors Located postsynaptically in the effector organs of the PSNS Smooth muscle Cardiac muscle Glands Named muscarinic because they can be stimulated by the alkaloid muscarine Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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Cholinergic Drugs: Mechanism of Action Direct-acting cholinergic agonists Bind to cholinergic receptors, activating them Indirect-acting cholinergic agonists Inhibit the enzyme acetylcholinesterase, which breaks down ACh Results in more ACh available at the receptors Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Indirect-Acting (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 to break these bonds Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Drug Effects Effects seen when PSNS is stimulated The PSNS is the “rest and digest” system Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Drug Effects (cont’d) Stimulate intestine and bladder Increased gastric secretions Increased gastrointestinal motility Increased urinary frequency Stimulate pupils Constriction (miosis) Reduced intraocular pressure Increased salivation and sweating Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Cholinergic Drug Effects (cont’d) Cardiovascular effects Decreased heart rate Vasodilation Respiratory effects Bronchial constriction, narrowed airways Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Cholinergic Drug Effects (cont’d) At recommended doses, cholinergics primarily affect muscarinic receptors At high doses, cholinergics stimulate nicotinic receptors Desired effects are from muscarinic receptor stimulation Many undesirable effects are caused by stimulation of nicotinic receptors Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question The nurse is assessing a patient who has been taking a cholinergic drug for 3 days. The patient has flushed skin, orthostatic blood pressure changes, and is complaining of abdominal cramps and nausea. The nurse recognizes that the patient is most likely experiencing early signs of a cholinergic crisis. late signs of a cholinergic crisis. an allergic reaction to the drug. expected adverse effects. Correct answer: A Rationale: The items listed are early signs of a cholinergic crisis, which can become more severe and lead to hypotension, circulatory collapse, bloody diarrhea, shock, and cardiac arrest. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications Direct-acting drugs Reduce intraocular pressure Useful for glaucoma and intraocular surgery echothiophate carbachol pilocarpine Topical application because of poor oral absorption Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications (cont’d) Direct-acting drug—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 subcutaneous injection Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications (cont’d) Indirect-acting drugs Cause skeletal muscle contractions Used for diagnosis and treatment of myasthenia gravis Used to reverse neuromuscular blocking drugs Used to reverse anticholinergic poisoning (antidote) Examples: physostigmine, pyridostigmine Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications (cont’d) Indirect-acting anticholinesterase drugs Used for treatment of mild to moderate Alzheimer’s disease donepezil (Aricept) galantamine (Razadyne) rivastigmine (Exelon) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications (cont’d) memantine (Namenda) Not a cholinergic drug Also used in the treatment of Alzheimer’s disease Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Adverse Effects Adverse effects are a result of overstimulation of the PSNS Cardiovascular Bradycardia, hypotension, syncope, conduction abnormalities (AV block and cardiac arrest) CNS Headache, dizziness, convulsions, ataxia Gastrointestinal Abdominal cramps, increased secretions, nausea, vomiting Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Adverse Effects (cont’d) Respiratory Increased bronchial secretions, bronchospasms Other Lacrimation, sweating, salivation, miosis Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Interactions Anticholinergics, antihistamines, sympathomimetics Antagonize cholinergic drugs, resulting in decreased responses Other cholinergic drugs Additive effects Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Herbal Products: Gingko Common uses Prevent memory loss Vertigo Tinnitus May cause GI upset, headache, bleeding Potential interactions Aspirin NSAIDs Anticoagulants Anticonvulsants Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A 60-year-old woman asks the nurse about taking ginkgo to help with her memory. The patient has a history of arthritis, type 2 diabetes, thyroid disease, and hypertension. She is currently taking NSAIDs for arthritis, oral antidiabetic medications, thyroid replacement hormone, and a beta blocker for blood pressure. What potential adverse effect from the gingko would be of most concern for this patient? Stomach upset Diarrhea Bleeding Drowsiness Correct answer: C Rationale: Potential adverse effects of gingko include stomach or intestinal upset, headache, bleeding, and allergic skin reaction. Potential drug interactions include aspirin, nonsteroidal antiinflammatory drugs (NSAIDs), anticoagulants, and other drugs. The ginkgo may interact with the NSAID medication and cause increased bleeding. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Nursing Implications Note that these drugs 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 vital signs and systems overview Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Nursing Implications (cont’d) Medications should be taken as ordered and not abruptly stopped Doses should be spread evenly apart to optimize the effects of the medication Overdosing can cause life-threatening problems. Patients should not adjust dosages unless directed by their health care provider Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient is scheduled to have lunch at 1200. The nurse will administer the pyridostigmine (Mestinon) at what time for optimal therapeutic effect? 1100 1130 1200 1230 Correct answer: B Rationale: The drug should be taken 30 minutes before a meal for maximal therapeutic effect. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Nursing Implications (cont’d) 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 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient with Alzheimer’s disease accidentally took 2 weeks’ worth of a cholinergic medication. He is brought to the emergency department, is going into shock, and experiencing severe hypotension and vomiting. The nurse will expect which initial treatment? Administration of physostigmine Administration of atropine Administration of epinephrine Cardiovascular support with dopamine Correct answer: B Rationale: Atropine can be given to reverse the effects of an overdose of a cholinergic drug. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Nursing Implications (cont’d) Atropine is the antidote for cholinergics, and 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 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Nursing Implications (cont’d) Monitor for therapeutic effects Alleviated signs and symptoms of myasthenia gravis In postoperative patients with decreased GI peristalsis, monitor for: Increased bowel sounds Passage of flatus Occurrence of bowel movements Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Nursing Implications (cont’d) Monitor for therapeutic effects In patients with urinary retention/hypotonic bladder, urination should occur within 60 minutes of bethanechol administration In patients with Alzheimer’s disease: Improvement in symptoms Improvement in mood and decrease in confusion Monitor for adverse effects Copyright © 2014 by Mosby, an imprint of Elsevier Inc.