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 - prventing, 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