Topic 8 Cholinergic Meds (1) PDF

Topic 8. Autonomic Nervous System: Cholinergics NRSG-303-A1 Objectives 1. Briefly review the functions of the autonomic nervous system and the impact of the parasympathetic division. 2. List the various drugs classified as cholinergic agonists (also called parasympathomimetics). 3....

Topic 8. Autonomic Nervous System: Cholinergics NRSG-303-A1 Objectives 1. Briefly review the functions of the autonomic nervous system and the impact of the parasympathetic division. 2. List the various drugs classified as cholinergic agonists (also called parasympathomimetics). 3. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions, contraindications, dosages, routes of administration, and any antidotal management for the various cholinergic agonists (or parasympathomimetics) 4. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions, contraindications, dosages, routes of administration, and any antidotal management for the cholinergic antagonists. 5. Develop a collaborative plan of care that includes all phases of the nursing process for patients taking cholinergic antagonists.  Drugs that stimulate the parasympathetic nervous system (the opposing system to the sympathetic nervous system) Cholinergic Also known as cholinergic agonists or Drugs parasympathomimetics Mimic effects of the parasympathetic nervous system neurotransmitter acetylcholine (ACh) Cholinergic Receptors Two types, Location determined Action once stimulated by: Nicotinic Ganglia receptors Smooth muscle Muscarinic Cardiac muscle receptors Glands  Direct-acting cholinergic agonists Bind to cholinergic receptors, activating them Cholinergic Drugs: Indirect-acting cholinergic agonists Mechanism of Also known as cholinesterase inhibitors Action Inhibit the enzyme acetylcholinesterase, which breaks down ACh Results in more ACh available at the receptors  Reversible Bind to cholinesterase for a short period of time Indirect-Acting Irreversible (Cholinesterase Inhibitors) Bind to cholinesterase for a long period of time Bind to cholinesterase and form a permanent covalent bond The body must make new cholinesterase to break these bonds.  Stimulate intestine and bladder Increased gastric secretions Increased gastrointestinal motility Increased urinary frequency Stimulate pupils Drug Effects Constriction (miosis) Reduced intraocular pressure Increased salivation and sweating Cardiovascular effects Decreased heart rate Vasodilation Respiratory effects Bronchial constriction, narrowed airways  At recommended doses, cholinergics primarily affect muscarinic receptors. At high doses, cholinergics stimulate Cholinergic nicotinic receptors. Drug Effects Desired effects are from muscarinic receptor stimulation. Many undesirable effects are caused by stimulation of nicotinic receptors.  Direct-acting drugs Reduce intraocular pressure Useful for glaucoma and intraocular surgery carbachol Indications pilocarpine Topical application because of poor oral absorption Direct-acting drug: succinylcholine Used as a neuromuscular blocker in general anaesthesia Intravenous  Indirect-acting drugs Increase ACh concentrations at the receptor sites, which leads to stimulation of the effector cells Cause skeletal muscle contractions Indications Used for diagnosis and treatment of myasthenia gravis Used to reverse neuromuscular blocking drugs Used to reverse anticholinergic poisoning (antidote) Example: physostigmine Indications Indirect-acting anticholinesterase drugs Used for treatment of mild to moderate Alzheimer’s disease donepezil (Aricept®) galantamine (Reminyl®) rivastigmine hydrogen tartrate (Exelon®)  Known drug allergy GI or genitourinary (GU) tract obstruction Bradycardia Defects in cardiac impulse conduction Contraindications Hyperthyroidism Epilepsy Hypotension Chronic obstructive pulmonary disease Parkinson’s disease Adverse Effects (1 of 2) Adverse effects are a result of overstimulation of the parasympathetic system. Bradycardia, hypotension, syncope, conduction abnormalities Cardiovascular (atrioventricular block and cardiac arrest) Central nervous system Headache, dizziness, convulsions, ataxia Abdominal cramps, increased secretions, nausea, vomiting, Gastrointestinal diarrhea, weight loss Respiratory Increased bronchial secretions, bronchospasms Other Lacrimation, sweating, salivation, miosis  Circulatory collapse, hypotension hypotension, bloody diarrhea, Treatment??? shock, and cardiac arrest. SLUDGE (salivation, lacrimation, urinary incontinence, diarrhea, Cholinergic gastrointestinal cramps, and emesis) Crisis Early signs Abdominal cramps, salivation, flushing of the skin, nausea and vomiting, transient syncope, transient complete heart block, dyspnea, and orthostatic  Anticholinergics, antihistamines, sympathomimetics Antagonize cholinergic drugs, resulting in Interactions decreased responses Other cholinergic drugs Additive effects  Cholinesterase inhibitor that works centrally in the brain to increase levels of ACh by inhibiting acetylcholinesterase donepezil Used in the treatment of mild to (Aricept) moderate Alzheimer’s disease Similar cholinesterase inhibitors include galantamine and rivastigmine.  Contraindications: known drug allergy Adverse effects: GI upset (including ulcer risk caused by increased gastric secretions), drowsiness, dizziness, insomnia, and muscle donepezil cramps. The effects on the cardiovascular system are complex and may include bradycardia, (Aricept) syncope, hypotension with reflex tachycardia, or hypertension. Interacting drugs: anticholinergics (counteract donepezil effects) and nonsteroidal anti- inflammatory drugs (NSAIDs)  Note that these drugs will stimulate the Note parasympathetic nervous system and mimic the action of ACh. Nursing Implications Assess Assess for allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease, and coronary artery disease. Perform baseline assessment of vital signs and Perform systems overview.  Medications should be taken as ordered and not abruptly stopped. Nursing Implications 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.  To help improve chewing and swallowing, encourage patients with myasthenia gravis to take medication 30 minutes before eating. Nursing When cholinergic drugs are prescribed for Alzheimer’s disease, be honest with caregivers Implications and patients and tell them that the drugs are for the management of symptoms, not a cure. Therapeutic effects of anti-Alzheimer’s drugs may not occur for up to 6 weeks. Nursing Implications 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  Monitor for therapeutic effects. In patients with urinary retention or hypotonic bladder, urination should occur within 60 minutes of bethanechol Nursing administration. Implications In patients with Alzheimer’s disease: Improvement in symptoms Improvement in mood and decrease in confusion Monitor for adverse effects. Cholinergic-Blocking Drugs Cholinergic-Blocking Drugs: Examples Natural Plant Alkaloids atropine sulphate belladonna scopolamine hydrobromide Synthetic and semisynthetic dicyclomine (Bentylol®) glycopyrrolate oxybutynin (Ditropan®) tolterodine (Detrol®) Others Cholinergic- Blocking Drugs Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS) Also known as anticholinergics, parasympatholytics, and antimuscarinic drugs MOA Competitive antagonists Compete with ACh for binding at muscarinic receptors in the PSNS Drug Effects (1 of 3) Cardiovascular Small doses: decreased heart rate Large doses: increased heart rate Central nervous system (CNS) Small doses: decreased muscle rigidity and tremors Large dose: drowsiness, disorientation, hallucinations Drug Effects (2 of 3) Eye Dilated pupils (mydriasis) Decreased accommodation caused by paralysis of ciliary muscles (cycloplegia) Gastrointestinal (GI) Relaxed smooth muscle tone of GI tract Decreased intestinal and gastric secretions Decreased motility and peristalsis Drug Effects Genitourinary (GU) Glandular Respiratory Relaxed detrusor muscle Decreased sweating Decreased bronchial Increased constriction of secretions internal sphincter Result: urinary retention Indications: Central Nervous System Decreasing muscle rigidity and muscle tremors Parkinson’s disease Drug-induced extrapyramidal reactions such as those associated with antipsychotic drugs Cv: Affects the heart’s conduction system Low doses: slow the heart rate High doses: block inhibitory vagal effects on sinoatrial and atrioventricular node pacemaker cells Results in increased heart rate Indications: Cardiovascular (2 of 2) Atropine Used primarily for cardiovascular disorders Diagnosis of sinus node dysfunction Symptomatic second-degree heart block Severe sinus bradycardia with hemodynamic compromise (advanced life support) Indications: Respiratory Blocking the cholinergic stimulation of the PSNS allows unopposed action of the sympathetic nervous system. Results Decreased secretions from the nose, mouth, pharynx, and bronchi Relaxed smooth muscles in the bronchi and bronchioles Decreased airway resistance Bronchodilation Indications: Respiratory Cholinergic blockers are used to treat: Exercise-induced bronchospasms Asthma Chronic obstructive pulmonary disease Indications: Gastrointestinal The PSNS controls gastric secretions and smooth muscles that produce gastric motility. Decreased secretions Blockade of PSNS results in: Relaxation of smooth muscle Decreased GI motility and peristalsis Irritable bowel disease GI drugs are used to treat: GI hypersecretory states Contraindications Known drug allergy Angle-closure glaucoma Acute asthma or other respiratory distress Myasthenia gravis Acute cardiovascular instability GI or GU tract obstruction (e.g., benign prostatic hyperplasia [BPH]) or illness  Adverse Effects Body system/adverse effects Cardiovascular: Increased heart rate, dysrhythmias CNS: CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium Eye: Dilated pupils (causing blurred vision), increased intraocular pressure GI: Decreased salivation, decreased gastric secretions, decreased motility (causing constipation) GU: Urinary retention Glandular: Decreased sweating Respiratory: Decreased bronchial secretions Interactions Amantadine, antihistamines, phenothiazines, digoxin When the above drugs are given with other cholinergic-blocking drugs, cause additive cholinergic effects, resulting in increased effects Atropine Naturally occurring antimuscarinic Uses: bradycardia, ventricular asystole, antidote for anticholinesterase inhibitor toxicity or poisoning, and preoperatively to reduce salivation and GI secretions Contraindications: angle-closure glaucoma, advanced hepatic and renal dysfunction, hiatal hernia associated with reflux esophagitis, intestinal atony, obstructive GI or GU conditions, and severe ulcerative colitis  Glycopyrrolate Synthetic antimuscarinic drug Blocks receptor sites in the autonomic nervous system that control the production of secretions Use: preoperatively to reduce salivation and excessive secretions in the respiratory and GI tracts Contraindications: hypersensitivity, angle-closure glaucoma, myasthenia gravis, GI or GU tract obstruction, tachycardia, myocardial ischemia, hepatic disease, ulcerative colitis, and toxic megacolon oxybutynin (Ditropan®) Synthetic antimuscarinic drug Uses: overactive bladder and antispasmodic for neurogenic bladder associated with spinal cord injuries and congenital conditions such as spina bifida Contraindications: drug allergy, urinary or gastric retention, and uncontrolled angle-closure glaucoma Nursing Implications (1 of 7) Keep in mind that these drugs block the action of ACh in the PSNS. Assess for allergies, presence of BPH, urinary retention, glaucoma, tachycardia, myocardial infarction, heart failure, hiatal hernia, and GI or GU obstruction. Perform baseline assessment of vital signs and systems overview. Nursing Implications Medications should be taken exactly as prescribed to have the maximum therapeutic effect. Overdosing can cause life-threatening problems. Blurred vision will cause problems with driving or operating machinery. Nursing Implications Patients may experience sensitivity to light and may want to wear dark glasses or sunglasses. When giving ophthalmic solutions, apply pressure to the inner canthus to prevent systemic absorption. Nursing Implications Patients should check with Dry mouth may occur; can the physician before taking be handled by chewing Antidote for atropine any other medication, gum, frequent mouth care, overdose is physostigmine. including over-the-counter and hard candy. medications. Nursing Implications Anticholinergics taken by older adult patients may lead to higher risk for heatstroke because of the effects on heat-regulating mechanisms. Teach patients to limit physical exertion and to avoid high temperatures and strenuous exercise. Emphasize the importance of adequate fluid intake. Nursing Implications Monitor for therapeutic effects. Monitor for adverse effects. For patients with Parkinson’s disease: fewer tremors and decreased salivation and drooling For patients with urological problems: improved urinary patterns, less hypermotility, increased time between voiding Objectives 1. Briefly review the functions of the autonomic nervous system and the impact of the parasympathetic division. 2. List the various drugs classified as cholinergic agonists (also called parasympathomimetics). 3. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions, contraindications, dosages, routes of administration, and any antidotal management for the various cholinergic agonists (or parasympathomimetics) 4. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions, contraindications, dosages, routes of administration, and any antidotal management for the cholinergic antagonists. 5. Develop a collaborative plan of care that includes all phases of the nursing process for patients taking cholinergic antagonists.