Drugs Affecting the Autonomic Nervous System Cholinergic Drugs Drugs Affecting the Autonomic Nervous System

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.

Cholinergic Drugs Drugs that stimulate the parasympathetic 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

Cholinergic Drugs Mechanism 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

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

Cholinergic Drugs Drug 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

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

Cholinergic Drugs Indications Direct-acting drugs Reduce intraocular pressure Topical useful for glaucoma and intraocular surgery pilocarpine

Cholinergic Drugs Indications 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

Cholinergic Drugs Indications 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)

Cholinergic Drugs Indications Indirect-acting drugs—cevimeline (Evoxac) Used to treat xerostomia (dry mouth) resulting from Sjögren’s syndrome

Cholinergic Drugs Adverse 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

Cholinergic Drugs Interactions Anticholinergics, antihistamines, sympathomimetics Antagonize cholinergic drugs, resulting in decreased responses Other cholinergic drugs Additive effects

Cholinergic Drugs Nursing 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

Cholinergic Drugs Nursing 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

Cholinergic Drugs 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 bethanechol administration ALSO monitor for adverse effects