Week 2 Notes PNS Lecture

Week 1: PNS NEED TO KNOW MEDS Muscarinic agonist: Bethanechol Muscarinic antagonist: Atropine Catecholamines: Epinephrine, Norepinephrine, Dopamine Non-catecholamines: Phenylephrine, Albuterol Alpha Antagonists (Blockers): Prazosin, Terazosin, Tamsulosin Beta Blockers: Metoprolol, Propranolol Neuropharmacology: The study of drugs that alter processes controlled by the nervous system; range of uses two broad categories: Peripheral nervous system drugs and Central nervous system drugs Axonal conduction: non selective!!! Works on all nerves it has access to Example: local anaesthetic reduces axonal conduction , limited uses work the same on all nerves they touch Limited uses synaptic transmission: highly selective!!! Synapses differ from one another unlike axons; customize drug design . Cardiac meds, GI meds, pain meds Selectivity: why is it important? Able to alter a specific disease process while leaving other physiologic processes unaffected Receptor binding Neurons affect cells by altering receptor activity on the target cell. Neurons release neurotransmitter molecules which diffuse across the synaptic gap and bind to receptors on target cell ( Receptors = receivers; design drugs to mimic them ) Agonist: activator; Mimic the action, Produce a functional response, Directly activate receptors Antagonist: blocker; Block an action, Inhibit a functional response, Prevent receptor activation Selective: less side effects Non selective: more side effects CH 15: PNS Major subdivisions: the somatic motor system - motor the autonomic nervous system automatic Autonomic – SNS (sympathetic) and PSNS (parasympathetic) Three principal functions of Autonomic Nervous System Heart Secretory glands - salivary, gastric, sweat, bronchial Smooth muscles - bronchi, blood vessels, urogenital system, GI tract SNS: stress; fight or flight! Regulation of C ardiovascular system, Regulation of body temperature , "fight or flight" Specifics : more blood flow to brain and muscles, vasoconstriction to maintain BP or elevate it; inc HR, lungs dilate (bronchodilation), pupils dilate to see far away, mobilize energy stores PSNS: peace; rest and digest digestion of food and excretion of wastes Controls near vision; miosis (pupil dilation) conserves energy by reducing cardiac work; slow HR Bronchial constriction; lungs don’t need to dilate and therefore relax Knowledge check: S = SNS P = PSNS CH 16-17: Neurotransmitters of the Peripheral Nervous System Acetylcholine: Employed at most junctions of the peripheral nervous system Norepinephrine: Released by most postganglionic neurons Epinephrine: Released by the adrenal medulla Receptors of the Peripheral Nervous System Cholinergic receptors : Mediate response to acetylcholine Muscarinic Adrenergic receptors : Mediate responses by epinephrine and norepinephrine Beta 1, Beta 2, Dopamine Cholinergic Drugs: mimic PNS Muscarinic agonists -- BETHANECHOL - WET Increase urination, tears, saliva, gastric motility Anticholinergic Drugs: Muscarinic antagonists -- ATROPENE - DRY Urinary retention, constipation, blurred vision, dry mouth Do not use with glaucoma Bethanechol: (Muscarinic agonist) Activates muscarinic receptors give one hour before or two hours after a meal; monitor for urinary output/retention Treats urinary retention (monitor output) Atropine (Muscarinic antagonist/ blocker of muscarinic receptors) Primarily work on muscarinic receptors; Blocks receptor activation by acetylcholine Eye surgery and to treat bradycardia , especially during surgery NOT TO USE WITH GLAUCOMA Effects: Increase HR, Pupil dilation, interferes with voiding, Decrease secretions/ lung/salivary glands, Slow down GI tract, Decrease sweating. *** Cant see, pee, sweat or shit REVIEW What is the Muscarinic Agonist (Cholinergic)? Bethanechol Uses: – urinary retention, What is the Muscarinic Antagonist (Anti-cholinergic)? Atropine Uses: Eye surgery, bradycardia, surgery Side effects: HR, pupil dilation, voiding interference, decreased secretions, slow GI , decreased sweating Cholinergic receptors mediate response to what neurotransmitter? Acetylcholine CH 20: Adrenergic receptors: Mediate responses by epinephrine and norepinephrine Adrenergic Agonists - activate the adrenergic receptors and as the dose increases, the drugs lose specificity They activate the SYMPATHETIC nervous system which is the fight or flight reaction They are used for many things such as asthma, CHF, and preterm labor Produce their effects by activating adrenergic receptors; Specificity is dose dependent ; fight or flight Adrenergic Agonists Overview Catecholamines Cannot be used orally Brief duration of action , often requires continuous IV infusion Cannot cross the blood-brain barrier (polar molecules) Epinephrine, Norepinephrine, Dopamine NSG: IV, watch for tissue necrosis Non-catecholamines Can be given orally Metabolized slowly, longer half-life More able to cross the blood-brain barrier Phenylephrine, Albuterol Adrenergic Agonists: Catecholamines (short acting) Epinephrine: Activates a1, a2, b1, b2 - short acting!! Treat some types of dysrhythmias Prolong effects of anesthetic --> used with lydocane Bronchodilation; treatment for anaphylaxis Adverse: hypertensive crisis, dysrhythmias (esp in hyperthyroid patients), necrosis d/t extravasation of IV NSG: Monitor for BP, HR, lung sounds. IV: need continuous cardiac monitoring Educate patients: For anaphylaxis: Inject IM into outer thigh, STAT Norepinephrine: NO beta2 activation; receptorsdoes not work for lungs; not used for anaphalaxis!!!) severe hypotension; treatment of shock Dopamine: Beta2 Agonist; treatment of shock; Dose-dependent receptor specificity Low: dopamine receptors only Mod: dopamine and Beta 1 receptors High: dopamine, beta 1 and alpha 1 Adrenergic Agonist: Non-catecholamines Phenylephrine - Alpha1 Agonist locally to reduce nasal congestion parenterally to elevate blood pressure. Eye drops can be used to dilate the pupil. Albuterol: Beta2 Agonist Bronchodilation: Asthma attacks Adverse effects : Tremor is most common If dosage is excessive, albuterol can cause tachycardia by activating beta1 receptors in the heart (looses selectivity) Contraindication – Dysrhythmia REVIEW: Adrenergic Receptors Which neurotransmitters: Epinepherine and Norepinepherine What are the classes of Adrenergic Agonists? Cats and Non-cats CH 21: Adrenergic Antagonists Alpha Antagonists (Blockers) Prazosin tx for Hypertension Adverse: OH, reflex tachycardia, (different process) congestion NSG: Administer first dose at bedtime, First dose effect, Watch for signs of orthostatic hypotension, escort to the bathroom First dose effect: Pt Passes out, why take at bed time Doxazosin : tx HTN and BPH Adverse: Orthostatic Hypotension, reflex tachycardia, congestion NSG: Start low dose and titrate up as needed to treat, Give first dose at night. Routine dose in am; First dose effect, Watch for signs of orthostatic hypotension, escort to the bathroom Tamsulosin : only used for BPH; no BP effects Adverse: drowsiness, dizziness, abnormal ejaculation Admin: Give 30 minutes after the same meal each day, DO NOT CRUSH or open caps Beta Blockers Propranolol : 1st gen; blocks both beta1 and beta 2 (non-selective) Indications: HTN, Angina, cardiac dysrhythmias, MI Adverse effects: Bradycardia, AV heart block, heart failure, Rebound cardiac excitation, bronchoconstriction (ONLY ONE different than Metoprolol) NSG: Do NOT stop abruptly, Can cause/exacerbate depression. Can mask signs of hypoglycemia, Determine heart rate before administering Do not give to asthma patients (affects the lungs, can cause bronchoconstriction) Metoprolol : 2nd gen; Normal doses : blocks beta1 high doses: can affect beta 2 Indications: HTN, Angina, cardiac dysrhythmias, MI Adverse effects: Bradycardia, AV heart block, heart failure, Rebound cardiac excitation NSG : Do NOT stop abruptly, determine heart rate before administering , Can mask signs of hypoglycemia, Preferable for diabetic patients because it is cardio-selective (beta1 only)