Autonomic Nervous System Medications (PDF)

Medications that affect the autonomic nervous system Adrenergic and Cholinergic Drugs Neurotransmitters - Chemical messengers that your body can’t function without o Their job is to carry chemical signal (messages) from one neuron (nerve cell) to the next target cell The next target cell can be anot...

Medications that affect the autonomic nervous system Adrenergic and Cholinergic Drugs Neurotransmitters - Chemical messengers that your body can’t function without o Their job is to carry chemical signal (messages) from one neuron (nerve cell) to the next target cell The next target cell can be another nerve cell, a muscle cell or a gland 3 Main functions of Neurotransmitters 1. Excitatory neurotransmitters: encourage a target cell to take action 2. Inhibitory neurotransmitters: decrease the chances of the target cell taking action. In come cases, these neurotransmitters have a relaxation-like effect. 3. Modulatory neurotransmitters can send messages to many neurons at the same time. Autonomic Nervous System Involuntary division of the nervous system - Consists of autonomic neurons that conduct impulses from the central nervous system (brain and/or spinal cord) to glands, smooth muscle and cardiac muscle. - ANS helps to maintain muscle and cardiac muscle - ANS helps to maintain internal homeostasis - ANS neurons are “always on”, functioning unconsiously and responsible for: o Regulating hormone secretion from glands to keep levels in check (i.e. thyroid, adrenal, salivary glands, etc.) o Respiration to keep gas exchange balanced o Regulation of heart rate and circulation (thus perfusion) o Digestion via peristalsis (contraction of smooth muscle in the digestive tract) and excertion Sympathetic= ‘fight or flight’ = Adrenergic receptors (activated by NTs: Norepinephrine, epinephrine, dopamine) Sympathetic and Parasympathetic nervous system are counterparts = opposites Parasympathetic = ‘rest and digest’ = Cholinergic receptors (activated by NT: acetylcholine) 4 actions of ANS - Sympathetic nervous system o Stimulate o Inhibit - Parasympathetic nervous system o Stimulate o Inhibit Adrenergic Receptors • Adrenergic receptors function for the sympathetic neurotransmitters: 1. A adrenergic receptors (a1, a2) 2. B adrenergic receptors (B1, B2) 3. Dopaminergic receptors-respond only to dopamine A-adrenergic receptors Actions: vasoconstriction and CNS stimulation • a1: located on postsynaptic effector cells (the cell, muscle, or organ the nerve stimulates) • a2: located on presynpatic nerve terminals (the nerve that stimulates the effector cells) B-adrenergic receptors Actions: bronchial, GI, and uterine smooth muscle relaxation and cardiac stimulation • All are located on postsynaptic effector cells. • B1: located primarily in the heart • B2: located in smooth muscle of the bronchioles, arterioles, and visceral organs Dopaminergic receptors Actions: cause dilation of visceral or smooth blood vessels, resulting in increased blood flow • Respond only to dopamine Stimulate-Sympathetic Nervous System • Sympathetic agonist, sympathomimetics or adrenergic agonists • Catecholamines include: epinephrine, norepinephrine, dopamine Mimic the effects of SNS neurotransmitters, either: • Endogenous - Norepinephrine and epinephrine - excitatory - Dopamine - Excitatory and inhibitory • Exogenous/synthetic - Dobutamine, phenylephrine hydrochloride Direct-acting Sympathomimetic • Binds directly to the receptor and causes a physiological response Indirect-acting sympathomimetic • Causes release of catecholamine from storage sites (vesicles) in nerve endings • Catecholamine then binds to receptors and causes a physiological response Mixed-acting sympathomimetic • Directly stimulates the receptor by binding to it • Indirectly stimulates the receptor by causing the release of stored neurotransmitters from vesicles in the nerve endings SNS Drug effect • Stimulation of a1-adrenergic receptors on smooth muscles results in: • Vasoconstriction of blood vessels • Relaxation of GI smooth muscles (decreased motility) • Constriction of bladder sphincter • Contraction of uterus • Male ejaculation • Contraction of pupillary muscles of eye (dilation) Stimulation of a2-adrenergic receptors results in: • Controlling the release of neurotransmitters • Negative feedback loops Stimulation of B1-adrenergic receptors produces heart stimulation • increases force of contraction (positive inotropic effect) • Increased heart rate (positive chronotropic effect) • Increased conduction through AV node (positive dromotropic effect) Ino= force so change in force of contraction Chrono = time so positive chronotropic increases heart rate Dromo = running= impulse - change in the speed of impulse conduction through AV node Stimulation of B2-adrenergic receptors on the airways results in bronchodilation (relaxation of the bronchi). • Uterine relaxation • Glycogenolysis in the liver • Increased renin scretion in the kidney • Relaxation of GI smooth muscles (decreased motility) Indication Examples Treatment of asthma and bronchitis • Bronchiodilators - sitmulate B2 adrenergic receptors of bronchial smooth muscles • Ex. Salbutamol, salmeterol, terbutaline sulphate Treatment of nasal congestion • intranasal application constricts arterioles and reduces nasal blood flow (A1-adrenergic receptors) • Ex. Phenylephrine hydrochloride Reduction of intraocular pressure and dilation and dilation of pupils-treat glaucoma • a-adrenergic receptors • Ex. Dipivenfrin hydrochloride Used to support heart during cardiac failure or shock • a- and B- receptors affected • Vasoconstriction, vasopressors • Inotropes, Chronotropes, Dromotropes Examples • Epinephrine - nonselective B and A drug - B1 effect - increases heart rate, force of contraction - B2 effect - asthma and anaphylactic shock - Higher doses - vasoconstrict from a1-adrenergic receptor activity • Norepinephrine - presominantely a adrenergic effects • Dopamine - dopaminergic, B1 and A1 drug - Low doses - dopaminergic - increase blood flow to organs - Increased doses have B1 and A1 drug • • Dobutamine - B1 given continous IV (short half-life) Phenylephrine - primarily a adrenergic effects These are critical care related medications; some could be given in Code type situations (i.e. Code Blue) Epinephrine Naturally occurring catecholamine neurotransmitter Potent dopaminergic as well as ß1- and α1-adrenergic receptor activity Low dosages: can dilate blood vessels in the brain, heart, kidneys, and mesentery, which increases blood flow to these areas (dopaminergic receptor activity) Higher infusion rates: improve cardiac contractility and output (ß1adrenergic receptor activity) Highest doses: vasoconstriction (α1-adrenergic receptor activity) Norepinephrine (Levophed) Stimulates α-adrenergic receptors Causes vasoconstriction Direct-stimulating ß-adrenergic effects on the heart (ß1-adrenergic receptors) No stimulation to ß2-adrenergic receptors of the lung Treatment of hypotension and shock Administered by continuous infusion Dopamine Naturally occurring catecholamine neurotransmitter Potent dopaminergic as well as ß1- and α1-adrenergic receptor activity Low dosages: can dilate blood vessels in the brain, heart, kidneys, and mesentery, which increases blood flow to these areas (dopaminergic receptor activity) Higher infusion rates: improve cardiac contractility and output (ß1adrenergic receptor activity) Highest doses: vasoconstriction (α1-adrenergic receptor activity) Dobutamine Selective vasoactive ß1-adrenergic drug that is structurally similar to the naturally occurring catecholamine dopamine Stimulates ß1-receptors on heart muscle (myocardium); increases cardiac output by increasing contractility (positive inotropy), which increases stroke volume, especially in patients with heart failure. Intravenous drug; given by continuous infusion Phenylephrine Works almost exclusively on the α-adrenergic receptors Used primarily for short-term treatment to raise blood pressure in patients who are in shock Control of supraventricular tachycardias Vasoconstriction in regional anaesthesia Topical ophthalmic drug Nasal decongestant Contraindications • Drug allergy • Severe hypertension • Tachycardia at baseline • Hx of dysrhythmias Adverse Effects • Chest pain • Hypertension • Tachycardia • Palitations or disrhythmias • Dry mouth • N/V Nursing Process Assessment • Medication hx • Allergies • Hx of asthma • Cardiac hx • Thorough cardiac assessment • Baseline VS • Remember if giving a medication that affects B-receptors, lungs and heart will be impacted • IV Evaluation • Improved cardiac output • Normal VS - Gradual increase in BP • Improved skin Color - As circulation improves • Temperature from cool to warm • Improved peripheral pulses • Increased LOC • Improved breath sounds Q&A Which medication is appropriate for a patient with asthma who is short of breath? • salbutamol • Salmeterol • Formoterol A 10 year old child is brought to the ER while having an asthma attack. The child is given a nebulizer treatment with salbutamol. The nurses immediate assessment priority would be to: • Determine the time of the childs last meal • Monitor sp02 with a pulse oximeter • Monitor childs temperature • Provide education on asthma management Adrenergic-Blocking Drugs • Adrenergic antagonists (opposite effect of adrenergic drugs) • Binds to adrenergic receptors but inhibit or block stimulation of the SNS - A and B blockers - Classified by the type of adrenergic receptor they block - (i.e. alpha-blockers, beta-blockers, etc.) A-Blockers Drug effects and some indications • Vasodilation: treat HTN • Decrease resistance to urinary flow : treat benign prostatic hyperplasia (BPH) (receptors in the prostate portion) Contraindications • Drug allergy • Hypotension • Sepsis Adverse effects • Severe and sudden drop in BP • Orthostatic hypotension Examples - A-Blockers • Doxazosin (cardura) - treat HTN • Prazosin (minipress) - treat BPH • Tamsulosin (flomax) - treat BPH, exclusively used for male pts B-Blockers Cardiioselective B-blockers or B1 blockers • Reduce stimulation to heart • Decrease HR • Decrease myocardial contractility, thus reducing myocardial oxygen demand OR Nonselective b-blockers (b1 and B2) • Cause same effects on heart as above • constrict bronchioles, resulting in narrowing of airways and shortness of breath Indications - B-Blockers Angina, MI, hypertension • decrease demand for myocardial oxygen Cardioprotective • inhibits stimulatio from circulating catecholamines dysrhythmias Glaucoma (topical use) Migraine headache Contraindications • Drug allergy • Heart block or bradycardia • Cardiogenic shock • Acute decompensated heart failure (pulmonary edema) • Respiratory distress ——-COPD • peripheral vascular disease (PVD) Adverse Effects Hypoglycemia • B2 receptors induce glucose production, when blocked can cause hypoglycemia Bradycardia (only an issue when symptomatic) Erectile dysfunction (ED) (for some) Lethargy (for some) Examples - B-Blockers • Atenolol - cardioselective b-blocker - HTN, angina • Carvedilol - a and B blocker - Heart failure • Labetalol - a and B blocker - HTV, given IV for severe HTN • Metoprolol - B1 blocker - Angina, HTN, MI • Propanolol - B-blocker - Angina, HTN, dysrhythmias • Sotalol - B- Blocker - Life threatening ventricular dysrhythmias, common after open heart surgery Nursing Process Assessment • Cardiac (re)assessment • Cardiac hx • Allergies • Medications • Blood glucose levels • Daily weights • Breath sounds Evaluation Therapeutic effects: • Decreased BP • Decreased HR • Decreased palpitations or chest pain Report any adverse effects, hypotension, bradycardia, heart failure Teaching Points • Encourage patients to take medications as prescribed and seek consultation if needed • Instruct patients that these medications should never be stopped abruptly • Teach patients to change positions slowly to prevent or minimize postural hypotension • If ED occurs, report as can impact quality of life • Instruct patients to notify their physicians if any adverse effects are present = palpitations, dyspnea, nausea, or vomiting occurs. • Inform patients that they may notice a decrease in tolerance for exercise and have patients notify their physicians of these problems occur Inform patients to report the following to their physicians: • Weight gain of more than 1 kg in 24 hours or 2.3 kg in 1 week • Edema of the feet or ankles • SOB • Excessive fatigue or weakness • Syncope or dizziness Cholinergic Drugs • Cholinergic agonists or Parasympathomimetics or cholinesterase inhibitors • Mimic the effect of the PNS - Neurotransmitter: acetylcholine (Ach) - ‘rest and digest’ There are: • Direct-acting cholinergic agonists - bind to cholinergic receptors, activating them • indirect-acting cholinergic agonists (cholinesterase inhibitors) - inhibit the enzyme acetylcholinesterase, which breaks down ACh - Results in more ACh available at the receptors Cholinergic Receptors 1. Nicotinic receptors • Located in ganglia where presynaptic and postsynaptic nerve fibers meet • Many undesirable effects are due to nicotinic stimulation 2. Muscarinic receptors • located postsynaptically in the effector organs • Desired effects come from muscarinic receptor stimulation S- Salvation L- Lacrimation U- Urination D- Defecation G- GI motility E- Emesis Diarrhea Increase Urination Miosis (pinpoint pupils) Bradycardia Increase Emesis Increase Lacrimation Increase Lethargy Increase Salivation Indications Direct-acting drugs • Ach released • Ex. Pilocarpine - used topically to tx glaucoma Indirect-acting drugs • Increase Ach concentration at receptor sites • Ex. Donepezil (Aricept) for alzheimers — Increases Ach in brain by inhibiting cholinesterase — Does not stop progression of disease but enhance memory and learning capabilites Contraindications • drug allergy • GI or GU tract obstruction • Bradycardia • Hypotension • Diarrhea Adverse Effects • Syncope • Hypotension or hypertension • Bradycardia or tachycardia • Headache • Abdominal cramps • Increased bronchial secretions Management of Cholinergic Overdose Cholinergic Crisis • Causes profound weakness due to depolarization of the post synaptic membrane, which results in a type of neuromuscular blockade. • Causes: excessive salivation, abdominal cramps, diarrhea, excessive pulmonary secretions, bradycardia, and blurred vision • Reversible with = atropine sulphate —- cholinergic antagonist Nursing Implications Assessment • allergies • Presence of GI or GU obstructions • Baseline VS Teaching Points • Medications should not be stopped abruptly • Over-dosing can cause life-threatening problems • Cholinergic drugs in Alzheimer’s does not cure disease, are meant to manage symptoms • Therapeutic effects of anti-Alzheimer’s drugs may not occur for up to 6 weeks Cholinergic Blocking Drugs • Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system • Anticholinergics, cholinergic blockers, cholinergic antagonist Drug Effects CVS • small doses: Decrease HR • Large doses: Increase HR CNS • small dose: decreased muscle rigidity and tremors • Large dose: drowsiness, disorientation, hallucinations Gastrointestinal (GI) • Relaxed smooth muscle tone of GI tract • Decreased intestinal and gastric secretions • Decreased motility and peristalsis Some indications Decreases muscle rigidity and tremors • treat parkinsons Cardiovascular disorders • heart block and sinus bradycardia Genitourinary (GU) • Relaxed detrusor muscle • Increased constriction of internal sphincter • Result: urinary retention Respiratory • decreased secretions from nose, mouth, pharynx • Bronchodilation • Can treat asthma and COPD Glandular • Decreased sweating GI • Decreases gastric secretions and decreases GI motility • treats irritable bowel disease Respiratory • Decreased bronchial secretions Eye • Dilated pupils (mydriasis) Contraindications • Drug allergy • Glaucoma • Cardiovascular instability • BPH • Myasthenia gravis • GI or GU obstruction Adverse Effects • Increased HR • Dysrhythmias • Disorientation, delirium • Dilated pupils (causing blurred vision) • Decreased salivation • Decreased GI motility (cause constipation) • Urinary retention • Decreased bronchial secretions Anticholinergic Drugs Atropine • treat bradycardia and heart blocks Scopolamine • Prevention of motion sickness • Prevent postop N/V • Can use for end-of-life care to decrease secretions Glycopyrrolate • Used pre-op to reduce salivation and excessive secretions in the respiratory and GI tract • Can use for end of life care to decrease secretions Oxybutynin • Used for overactive bladder and antispasmodic for neurogenic bladder Nursing Implications • Assess for allergies and contraindications • Overdosing can cause life-threatening problems • Blurred vision will cause problems wth driving or operating machinery • Dry mouth may occur, can be handled by chewing gum, frequent mouth care, and hard candy Patients should report the following symptoms to their physician: • Urinary hesitancy or retention • Constipation • Tachycardia • Palpitations • Tremors • Confusion • Sedation • Decreased sweating (leading to hot, dry skin)