Pharmacology

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Pharmacology

• Unit II

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Autonomic Nervous System

• Parasympathetic nervous system
• Sympathetic nervous sytem

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Sympathetic and Parasympathetic

• Some organs may have opposing effects
• Male sex organs may have complementary effects
• Other organs only regulated by one blood
  vessels

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3 transmitters

• Acetylcholine
• Norepinephrine
• epinephrine

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Cholinergic receptors

• Nicotinic N
• Nicotinic M
• muscarinic

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Adrenergic receptors

• Alpha 1
• Alpha 2
• Beta 1
• Beta 2
• Dopamine

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Cholinergic Drugs

• Agents that influence the activity of cholinergic
  receptors
• Mimic or block actions of acetylcholine

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Six categories

• Muscarinic agonists mimic
• Muscarinic antagonists block
• Ganglionic stimulating mimic effects
• Ganglionic blocking block
• Neuromuscular blocking block acetylcholine
• Cholinesterase inhibitors prevent breakdown
  acetylcholine

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Muscarinic Agonists

• Bind to muscarinic receptors activation
• Bethanechol
• Bradycardia
• Increased secretion sweating, bronchial, GI
• Smooth muscle contraction
• Pupillary constriction and accommodation for near
  vision(contraction of ciliary muscle)

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• Principle indication urinary retention
• Should be given only orally or subcutaneously
  side effects increase with sc route
• Contraindicated in patients with gastric ulcers

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Pilocarpine

• Given for glaucoma

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Poisoning

• Mushrooms and medications
• Excessive salivation, bronchospasm, bradycardia,
  hypotension
• Atropine muscarinic blocking agent drug of
  choice to reverse signs of toxicity

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Muscarinic Antagonists

• Atropine also called anticholinergic
• Blocks the action of acetylcholine at muscarinic
  receptors

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Atropine

• Increases heart rate
• Decreases secretion
• Relaxation of smooth muscle bronchi, urinary
  bladder, GI tract
• Dilation of pupil
• Relaxes ciliary muscle focus far vision

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Atropine

• 3 hour half-life
• Orally, topically, injection
• Used to be used preoperatively to decrease
  tracheal secretions

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Adverse effects

• Dry mouth, constipation, blurred vision,
  increased intraocular pressure, urinary
  retention, tachycardia, asthma drying of
  secretions

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Scopolamine

• Produces sedation
• Suppresses emesis and motion sickness

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Dicyclomine

• Bentyl, Di-Spaz
• Used for irritable bowel

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Poisoning

• Antimuscarinic poisoning
• From belladonna, atropine, scopolamine, some
  antihistamines
• Dry mouth, blurred vision, hyperthermia,
  hallucinations, respiratory depression

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antidote

• Physostigmine an inhibitor of
  acetylcholinesterase
• Charcoal, syrup of ipecac

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Cholinesterase inhibitors

• Reversible neostigmine
• Indication myasthenia gravis autoimmune
  disorder nicotinic M receptors are reduced at
  neuromuscular junction

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• Reverse nondepolarizing neuromuscular blockade
• PACU

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Cholinergic crisis

• Overdose with cholinesterase inhibitors
• Increased bronchial secretions
• Respiratory failure
• Atropine may be helpful

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Irreversible

• Cholinesterase inhibitors found in insecticides
• Nerve gases
• Indication - glaucoma

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Neuromuscular blockers
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Adrenergic Agonists

• Sympathomimetics
• Activate adrenergic receptors catecholamines
  vs. noncatecholamines

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Catecholamines

• Norepinephrine
• Epinephrine
• Isoproterenol
• Dopamine
• Dobutamine

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Noncatecholamines

• Ephedrine
• Phenylephrine
• Terbutaline

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• Catacholamine receptor sites located throughout
  the body

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Alpha receptor sites

• Alpha-adrenergic receptor sites smooth muscle of
  blood vessels, GI tract, GU tract when
  stimulated produce vasoconstriction

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Beta 1

• Heart muscle
• Increase contractility - inotrope
• Increase heart rate - chronotrope
• Increase av and sa node conduction - dromotrope

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Beta 2

• Respiratory system located in bronchial smooth
  muscle
• Produce bronchial dilation
• Bronchodilator
• Would increase blood sugar in pts with diabetes

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Adrenergic antagonists

• Alpha blockade for essential hypertension
• Cause vasodilation
• Pheochromocytoma, reversal of toxicity from
  epinephrine, raynauds disease

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• Prazosin selective blockade minipress
• Terazosin hytrin
• Doxazosin - cardura

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• Phentolamine regitine nonselective
  pheochromocytoma - infiltration

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Beta blockade

• Angina
• Hypertension
• Cardiac dysrhythmias
• MI
• Heart failure
• hyperthyroidism

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Adverse effects

• Brady
• Decreased CO
• AV block
• Rebound cardiac excitation

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Adverse effects of beta2 blockade

• Bronchconstriction - asthma
• Inhibition of glycogenolysis
• Propranolol - Inderal

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Metoprolol

• Cardioselective only blocks beta 1 receptors
• At usual therapeutic doses

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Indirect-acting antiadrenergic agents

• Reduce stimulation of peripheral adrenergic
  receptors

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• Reserpine hypertension
• Clonidine centrally acting (Catapres)

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GI tract

• Alpha1 and beta2 receptor sites
• Increasing gastric motility
• Primarily anorexiants
• Dexadrine
• Methamphetamine (Desoxyn)

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• Also helpful for reducing intraocular pressure
  and dilating pupils
• Good for glaucoma

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