BASIC PRINCIPLES OF PERIPHERAL NERVOUS SYSTEM PHARMACOLOGY - PowerPoint PPT Presentation

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BASIC PRINCIPLES OF PERIPHERAL NERVOUS SYSTEM PHARMACOLOGY

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... adjuncts to anesthesia (preanesthetic medication, ... Atropine (preparation for anaesthesia, ophthalmic examination, bradycardia, ... INTRAVENOUS ANESTHESIA ... – PowerPoint PPT presentation

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Title: BASIC PRINCIPLES OF PERIPHERAL NERVOUS SYSTEM PHARMACOLOGY


1
BASIC PRINCIPLES OF PERIPHERAL NERVOUS SYSTEM
PHARMACOLOGY
  • Synaptic neurotransmission target of drugs
  • PNS somatic and autonomic divisions
  • Differences in neurotransmitters and receptors in
    the ANS

2
CHOLINERGIC DRUGS
  • ANS - parasympathetic cholinergic (muscarinic)
    synapses
  • effects of muscarinic agonists and antagonists
  • antimuscarinic side effects of some drugs
  • effects of anticholinesterase (cholinesterase
    inhibitor) drugs

3
CHOLINERGIC DRUGS
  • Drug action at the neuromuscular junction
    (nicotinic receptors)
  • muscle relaxation for surgery and ECT nicotinic
    receptor blockade
  • reversal of this neuromuscular blockade
    anticholinesterase drugs

4
ADRENERGIC DRUGS
  • ANS sympathetic division adrenergic synapses
  • receptor selectivity of adrenergic drugs
  • clinical use of adrenergic agonists and
    antagonists

5
LOCAL AND GENERAL ANAESTHESIA
  • 1. Local anestheticsa) classification and
    therapeutic usesb) adverse effects/ toxicityc)
    application topically injection (nerve block,
    IV regional anesthesia, epidural spinal
    anesthesia)

6
LOCAL AND GENERAL ANAESTHESIA
  • 2. General anesthetics a) types (i) inhalation
    agents (halothane, nitrous oxide) (ii)
    intravenous agents (barbiturates,
    benzodiazepines, opioid analgesics)b)
    stages of anesthesiac) basic pharmacologyd)
    adverse effects
  • e) adjuncts to anesthesia (preanesthetic
    medication, anticholinergic drugs, neuromuscular
    blocking agents, postanesthetic medications)

7
THE NERVOUS SYSTEM A REVIEW
  • Overall Functions - integration and homeostasis
  • Divisions - CNS PNS, PNS - somatic motor
    autonomic NS, ANS - parasympathetic sympathetic

8
PNS somatic and autonomic divisions
  • SOMATIC
  • comprises single neurone btw CNS effector
  • innervates skeletal muscle
  • always leads to muscle excitation
  • AUTONOMIC
  • two neurone chain btw CNS effector
  • innervates smooth cardiac muscle, glands and GI
    neurones
  • inhibition / excitation of effector cells

9
AUTONOMIC NERVOUS SYSTEM REVISITED
  • Functions of the ANS - regulation of heart,
    secretory glands (salivary, gastric, sweat),
    smooth muscle (bronchi, blood vessels,
    urogenital, GIT)
  • Effector Organs
  • Structure

10
COMPARISON OF SYMPATHETIC PARASYMPATHETIC NS
  • PARASYMPATHETIC NS
  • slow heart rate
  • increase gastricsecretion
  • emptying of bowel
  • emptying of bladder
  • accomodation
  • pupil constriction
  • SYMPATHETIC NS
  • regulation of the CV system
  • regulation of body temperature
  • fight or flight (fright) response

11
Synaptic Neurotransmission Target of Drugs
  • Neural synapses, initiation of action potentials
  • Neuropharmacology
  • Transmitter synthesis (increase, decrease)
  • Transmitter storage (deplete vesicles of
    transmitter, decrease receptor stimulation)
  • Transmitter release (promote, inhibit)
  • Receptor binding (agonist, antagonist)
  • Termination of transmitter action (block uptake,
    inhibit breakdown of transmitter)

12
Differences in neurotransmitters and receptors in
the ANS
  • NEUROTRANSMITTERS
  • RECEPTORS
  • ACETYLCHOLINE
  • NORADRENALINE
  • NICOTINIC, MUSCARINIC, alpha, beta receptor
    subtypes

13
CHOLINERGIC DRUGS
  • Effects of muscarinic agonists
  • Bethanecol (urinary retention and intestinal
    paralysis)
  • Effects of muscarinic antagonists
  • Atropine (preparation for anaesthesia, ophthalmic
    examination, bradycardia, biliary colic,
    intestinal hypermotility and muscarinic poisoning

14
CHOLINERGIC DRUGS
  • Antimuscarinic side effects of some drugs
  • - dry mouth, blurred vision photophobia,
    elevation of IOP, urinary retention,
    constipation, ansence of sweating, tachycardia,
    asthma (drying of bronchial secretions)
  • Effects of anticholinesterase (cholinesterase
    inhibitor) drugs
  • Neostigmine Physostigmine
  • muscarinic effects, myasthenia gravis

15
CHOLINERGIC DRUGS
  • Drug action at the neuromuscular junction
    (nicotinic receptors)
  • succinylcholine (depolarising)
  • binds to nicotinic receptors but does not
    immediately dissociate
  • muscle relaxation (preceded by tansient
    contractions and paralysis is shorter in
    duration)
  • tubocurarine (non-depolarising)
  • competes with Ach for nicotinic binding sites
  • muscle relaxation, hypotension, CNS (nil)
  • reversal of this neuromuscular blockade
    anticholinesterase drugs

16
ADRENERGIC DRUGS
  • Sympathomimetics
  • Mechanisms of receptor stimulation (direct,
    promote NA release, inhibit reuptake, inhibit NA
    metabolism, receptor selectivity)
  • Consequences of alpha and beta stimulation

17
Adrenergic Agonists ADRENALINE ISOPRENALINE
  • Clinical uses
  • delay absorption of local anaesthetic
  • control superficial bleeding
  • produce nasal congestion
  • elevate BP
  • mydriasis
  • AV heart block
  • myocardial arrest
  • shock
  • asthma (not routine)
  • Adverse effects
  • hypertensive crisis
  • arrythmias
  • angina
  • necrosis
  • hyperglycaemia

18
Adrenergic Antagonists Propranolol
Phentolamine
  • Adverse Effects
  • ALPHA BLOCKADE
  • postural hypotension
  • reflex tachycardia
  • nasal congestion
  • inhibition of ejaculation
  • BETA BLOCKADE
  • bradycardia
  • reduce CO
  • CHF
  • AV heart block
  • bronchial constriction
  • Clinical Uses
  • ALPHA BLOCKADE
  • hypertension
  • reversal of xs alpha stimulation
  • phaechromocytoma
  • BETA BLOCKADE
  • hypertension
  • angina pectoris
  • cardiac arrhythmias

19
Local Anesthetics
  • MECHANISM OF ACTION
  • blockade of axonal conduction (block Na
    channels), nonselective, temporal sequence (pain,
    cold, warmth, touch, deep pressure)
  • CLASSIFICATION
  • esters vs amide types
  • THERAPEUTIC USES
  • Localised loss of sensation
  • Use with vasoconstrictors

20
Local Anesthetics
  • ADVERSE EFFECTS / TOXICITY
  • CNS stimulation then depression
  • CVS vasodilation cardiac depression
  • allergy, hypersensitivity reactions (esters)
  • depress uterine contractions, bradycardia, CNS
    depression in neonate
  • APPLICATION- topical (surface skin mucous
    membranes) lignocaine, cocaine - by injection
    (nerve block, IV regional, epidural, spinal (SA)
    - hypotension

21
General Anesthetics
  • Types(i) inhalation agents (halothane, NO2)
  • suppression of neuronal activity of brain and
    spinal cord, not receptor mediated
  • index of potency MAC (low MAC high potency)
  • (ii) intravenous agents (barbiturates,
    benzodiazepines, opioid analgesics)
  • used alone or as adjunct to IH A
  • Thiopental, Diazepam,

22
Stages of Anesthesia
  • Stage of analgesia
  • Stage of delirium
  • Stage of surgical anesthesia
  • Stage of medullary paralysis

23
Basic Pharmacology
  • Neuronal effect
  • anesthetic disrupt membrane structure of nerves
  • interferes in action potential generation
  • is not a receptor-mediated process

24
Adverse Effects
  • INHALATIONAL ANESTHESIA
  • respiratory cardiac depression
  • sensitisation of the heart to catecholamines
    (halothane)
  • malignant hyperthermia (rare)
  • aspiration of gastric contents (loss of reflexes)
  • INTRAVENOUS ANESTHESIAextravasation can cause
    tissue damage, 24-hr hangover, cv respiratory
    depression, cv respiratory depression,
    unpleasant psychological reactions

25
Adjuncts to Anesthesia (preanesthetic medication)
  • Anticholinergic drugs (decrease secretions)
  • Anxiolytic agents (reduce anxiety)
  • Opioids or NO2 (analgesia)
  • Antiemetics
  • Neuromuscular blocking agents (muscle
    relaxation)
  • Post-anesthetic medications
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