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Peripheral Nervous System Drugs

Peripheral Nervous System Drugs. Sympathetic: (Adrenergic) Activators Sympthomimetics Agonists Blockers Sympatholytic Antagonists Receptors Alpha 1 & 2 Beta 1 & 2 Dopamine. Parasympathetic (Cholinergic) Activators Parasympathomimetics Agonists Blockers Anticholinergics

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Peripheral Nervous System Drugs

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  1. Peripheral Nervous System Drugs

  2. Sympathetic:(Adrenergic) Activators Sympthomimetics Agonists Blockers Sympatholytic Antagonists Receptors Alpha 1 & 2 Beta 1 & 2 Dopamine Parasympathetic(Cholinergic) Activators Parasympathomimetics Agonists Blockers Anticholinergics Antimuscarinics Parasympatholytics Antagonists Receptors Muscarinic Nicotinic N & M **Peripheral Nervous System Vocabulary**

  3. For the Test: Cholinergic Drugs • Muscarinic agonists: no agents • Muscarinic antagonists (anticholinergics): 7 agents see slide • Ganglionic blockers: no agents • Neuromuscular blockers: no agents • Cholinesterase inhibitors: neostigmine, physostigmine (difference and use)

  4. Muscarinic Agonists(Parasympathomimetics) • Limited uses: • Urinary retention • Increase GI peristalsis • Glaucoma, eye surgery • Adverse effects • Bradycardia, hypotension • Excess saliva, cramps, diarrhea • Urinary (contra: bladder obstruction &surgery) • Asthma exacerbation

  5. Muscarinic Poisoning • Sources • Muscarinic agonists • Cholinesterase inhibitors • Mushrooms • Symptoms • Profuse salivation, tearing, bronchospasm, diarrhea, bradycardia, hypotension • Treatment: atropine

  6. Muscarinic Antagonists (Parasympatholytics) • “Anticholinergics” • Agents to know forever • Atropine: strongest, general use • Oxybutinin (Ditropan): overactive bladder • Tolerodine (Detrol): overactive bladder • Scopolamine: sedation, motion sickness • Ipratropium, Tiotropium: lungs • Dicyclomine (Bentyl): IBS, diarrhea

  7. Atropine • Mechanism: blocks muscarinic receptors by competing with Acetylcholine • high doses will block nicotinic as well • Route: PO, topically (eye), injection

  8. Pharmacologic effects: ↑ heart rate ↓ secretions (GI, tear, salivary) ↓ smooth muscle (peristalsis, urination) Dilate eye (mydriasis) ↑ CNS excitability Therapeutic Uses Preanesthesia (make sure heart doesn’t stop) Eye surgery: (dilate eye) Bradycardia: ↑ heart rate Intestinal hypertonicity, hypermotility (slows GI tract) Muscarinic Agonist Poisoning (antidote) Atropine

  9. Adverse (Anticholinergic) EffectsMust Know: “Just too much effect” • Xerostomia (Dry Mouth) • Blurred vision, photophobia • Elevation of IOP • Urinary retention • Constipation • Anhidrosis (no sweat) • Tachycardia • Asthma: secretions too thick and crusty • Dementia

  10. Anticholinergic Toxicity • Dry as a bone • Red as a beat • Hot as a hare • Blind as a bat • Mad as a hatter • **Must determine whether psychosis is real or anticholinergic • Treatment: • Minimize absorption • Cholinesterase inhibitor

  11. Dose dependent Low dose High dose Glands: sweat, salivary, bronchial Heart Eye Bladder Intestine motility Lung Stomach Atropine

  12. Interactions • Drugs with anti-muscarinic (anticholinergic) side effects effects • Antihistamines • Phenothiazine antipsychotics • Tricyclic antidepressants • Furosemide (Lasix)

  13. Cholinesterase Inhibitors(Parasympathetic Agonists) • Increase Acetylcholine at all receptors! • Reversible (must know these agents) • Neostigmine: myasthenia gravis • Physostigmine: anti-cholinergic antidote • Irreversible (do not need to know for test) • Used as insecticides • Developed in WW2 as “nerve gas” • One is used for glaucoma (just trivia for you attorney types)

  14. Myasthenia Gravis • Etiology: Antibodies against Nicotinic-M receptors • Clinical manifestations: fatigue, muscular weakness, dyspnea • Treatment • Cholinesterase inhibitors • Side effects: can cause accumulation of acetylcholine and nicotinic-M and muscarinic receptors

  15. Myasthenia Gravis • Treatment • Side effects cont • Muscarinic effects • Neuromuscular blockade (toxicity)

  16. Neuromuscular Blockers • Neuromuscular Blockers • Paralyze muscle • Use to intubate so they don’t fight • Agents • Nondepolarizing: tubocurarine, et al. • Depolarizing: succinylcholine • Uses • Surgery • Mechanical Ventilation, ET intubation • Adjunct to ECT

  17. Adrenergic Drugs • Phenylephrine and Pseudoephedrine • Epinephrine, Norepi, Dopamine, Dobutamine • All lung beta-2 agonists • Alpha blockers: terazosin, phentolamine • Beta blockers: propanolol, metoprolol, atenolol, carvedilol • Indirect antagonists: Clonidine

  18. Catecholamines: Broken down by MAO and COMT in liver and intestine Parenteral only Cannot be given orally, short half-life Colorless solutions; color is sign of oxidation Natural catecholamines: epi, norepi, dopamine Synthetic: dobutamine (others we don’t need to know) Non-catecholamines Can be given PO Last longer in body Adrenergic Agonists Activate alpha and beta receptors

  19. Adrenergic Agonists • Noncatecholamines • Phenylephrine: (alpha1) nasal congestion, inotropic support (rare now) • Pseudoephedrine (all alpha and beta): • Nasal congestion • Can be used to make amphetamines

  20. Adrenergic AgonistsCatecholamine Receptor Specificity

  21. Alpha1 Activation • Therapeutic effects • Vasoconstriction • ↑ BP (intensive care, last resort) • Hemostasis • ↓ local anesthesia absorption • ↓Nasal decongestion • Mydriasis • Adverse effects • Hypertension • Necrosis • Bradycardia

  22. Beta1 Activation • Therapeutic Uses • Cardiac arrest (make heart beat again) • Heart Failure: inotropic support • Shock: inotropic and chronotropic support • A-V heart block (speed conductivity) • Adverse effects • ↑ HR • Angina pectoris • dysrhythmia

  23. Beta2 activation • Therapeutic use • Asthma: bronchodilate • Preterm labor: stop contraction • Adverse effects • Hyperglycemia • Tremor

  24. Therapeutic uses: ↓ absorption of local anesthetics Control superficial bleeding ↑ BP Mydriasis AV block, V. fib, Asystole Status Asthmaticus Anaphylactic shock Reduce nasal congestion Adverse events Hypertensive crisis Dysrythmias Angina pectoris Necrosis Hyperglycemia EpinephrineReceptors: all alpha and beta

  25. Epinephrine • Absorption • Inhalation: minimal • Injection • Preparations • SC, IM, IV, Intracardiac, intraspinal, inhalation, • Lidocaine with epi • No fingers, nose, penis, and toes • Inactivation: MAO and COMT in liver

  26. Epinephrine • Interactions • MAO inhibitors (why oh why?) • Alpha-adrenergic blocking agents • Beta-adrenergic blocking agents

  27. Dopamine • Receptor: dopamine, alpha1, (beta1 higher doses) • Therapeutic Uses • Shock: • ↑ HR and contractility • Maintain renal artery perfusion • Heart failure: same as above • ARF: low dose (may not be effective) • Adverse Effects • Dysrhythmias, angina pectoris

  28. Beta-2 agonists • Short acting • Albuterol • Levalbuterol • Long acting • Salmeterol • Formoterol

  29. Other Adrenergic Agonists • Dobutamine (beta1) uses • Shock (inotropic support) • Stress Echoes • Terbutaline: (beta2) uses • Stop preterm labor contractions

  30. Norepinephrine • Receptor: alpha 1 & 2, beta1 • Therapeutic uses • Hypotensive state • Cardiac arrest (last resort) • Brand: Levophed (Leave ‘em dead!)

  31. Adrenergic Antagonists Can be quite selective for receptors

  32. Therapeutic uses Hypertension BPH Reverse toxicity of epinephrine Pheochromocytoma(what is it?) Raynaud’s disease Adverse effects Orthostatic hypotension Reflex tachycardia Nasal Congestion Inhibition of ejaculation Na+ & H2O retention Alpha1-blockers

  33. Alpha-Adrenergic Blockers • Prazosin - HTN • Doxazosin – HTN, BPH • Terazosin – HTN, BPH • Tamsulosin – BPH • Phentolamine – Pheochromocytoma, tissue necrosis

  34. Therapeutic Uses MI HF Angina Pectoris Dysrhythmias HTN Other Hyperthyroid Migraine Stage Fright Pheochromocytoma Glaucoma Adverse Effects (β1) ↓ HR CO AV heart block Precipitate HF Rebound cardiac excitation Adverse Effects (β2) Bronchoconstriction Inhibition of glycogenolysis Beta-blockers

  35. Beta1, Beta2 Propanolol* Nadolol Pindolol Selective Metoprolol* Atenolol* Bisoprolol * Means must know Beta1,beta2, alpha1 Labetalol Carvedilol* Used for HF Metoprolol* Carvedilol* Beta Blockers Agentsby receptor selectivity

  36. Indirect Adrenergic Antagonists • Clonidine • activates alpha-2 receptors in CNS  ↓ norepinephrine release • Uses • Hypertension • Pain relief in cancer (epdidural use only) • Adverse effects • Drowsiness, dry mouth, rebound HTN, bradycardia • Preparations • Oral: at least twice a day • Transdermal: seven days

  37. Indirect Adrenergic Antagonists • Reserpine • Suppresses NE synthesis and promotes MAO-mediated destruction • Crosses BBB • Effects • Hypotension • Adverse effects • Depression, sedation, apathy • Bradycardia, hypotension • Guanethidine: similar but fewer CNS effect

  38. Indirect Adrenergic Antagonists • Methyldopa, Methyldopate • Similar to clonidine, but are taken up in brain stem neurons and converted to active alpha2 agonist • Use: HTN • Adverse effects • 10 – 20% Positive Coombs test (5%) will go on to have hemolytic anemia • Hepatotoxicity • Drowsiness, dry mouth, hypotension, etc.

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