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Drugs Affecting the Parasympathetic Nervous System. Drugs Affecting the Parasympathetic Nervous System. Parasympathetic Nervous System Neurotransmitter is ACH The receptors are called cholinergic receptors.

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drugs affecting the parasympathetic nervous system2
Drugs Affecting the Parasympathetic Nervous System

Parasympathetic Nervous System

  • Neurotransmitter is ACH
  • The receptors are called cholinergic receptors.
  • Drugs that bind to cholinergic receptors and produced effects similar to ACH are referred to as cholinergic drugs.
drugs affecting the parasympathetic nervous system3
Drugs Affecting the Parasympathetic Nervous System

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

Acetylcholinesterase

drugs affecting the parasympathetic nervous system4
Drugs Affecting the Parasympathetic Nervous System

Receptors

Muscarinic Receptors

Nicotinic Receptors

N-1

N-2

drugs affecting the parasympathetic nervous system5
Drugs Affecting the Parasympathetic Nervous System

Nicotinic Receptors

Nicotinic-II Receptors

Nicotinic-I Receptors

Found at ganglions of

Sympathetic and Parasympathetic

Post- ganglionic fibers

Found at Neuromuscular junction of

Skeletal muscles.

drugs affecting the parasympathetic nervous system6
Drugs Affecting the Parasympathetic Nervous System

Ganglion, Nicotinic I receptor

Sympathetic Fibers

Post-ganglionic Fiber

Pre-ganglionic Fiber

Adrenergic Receptor

Ganglion, Nicotinic I receptor

Parasympathetic Fibers

Pre-ganglionic Fiber

Post-ganglionic Fiber

Muscarinic Receptors

Somatic Fibers

Nicotinic II Receptors

drugs affecting the parasympathetic nervous system7
Drugs Affecting the Parasympathetic Nervous System

Nicotine

  • Alkaloid obtained from tobacco.
  • Stimulate the NI receptors at low doses.
  • Block the NII receptors at high doses.
drugs affecting the parasympathetic nervous system8
Drugs Affecting the Parasympathetic Nervous System

Nicotinic I

Drugs

Ganglionic

Stimulants

Ganglionic

Blockers

drugs affecting the parasympathetic nervous system9
Drugs Affecting the Parasympathetic Nervous System

Muscarinic Receptors

  • Found at the parasympathetic postganglionic nerve endings
  • Drugs that act like ACH at these receptors are referred to as cholinergic or muscarinic drugs.
  • Drugs that block ACH at the muscarinic receptors are referred to as anticholinergic or antimuscarinic drugs.
drugs affecting the parasympathetic nervous system10
Drugs Affecting the Parasympathetic Nervous System

Parasympathetic

Drugs

Cholinergic

Drugs

Anti-cholinergic

Drugs

drugs affecting the parasympathetic nervous system11
Drugs Affecting the Parasympathetic Nervous System

Cholinergic

Drugs

Direct Acting

Cholinergic Drugs

Indirect Acting

Cholinergic Drugs

drugs affecting the parasympathetic nervous system12
Drugs Affecting the Parasympathetic Nervous System

Direct Acting Cholinergic Drugs

  • Bind to muscarinic receptors.
  • Produces ACH like effect.
  • Slowly inactivated by acetylcholinesterase.
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Drugs Affecting the Parasympathetic Nervous System

Pharmocological Effects

  • Increase GI secretion and motility
  • Increase in genitourinary activity.
  • Bronchoconstriction
drugs affecting the parasympathetic nervous system14
Drugs Affecting the Parasympathetic Nervous System

Pharmocological Effects

  • Miosis
  • Vasodilatation (lower BP)
  • Decrease heart rate.
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Drugs Affecting the Parasympathetic Nervous System

Indirect Acting

Cholinergic Drugs

(Anticholinesterases)

Irreversible

Inhibitors

Reversible

Inhibitors

drugs affecting the parasympathetic nervous system17
Drugs Affecting the Parasympathetic Nervous System

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

ACH

Acetylcholinesterase

Anticholinesterases

drugs affecting the parasympathetic nervous system18
Drugs Affecting the Parasympathetic Nervous System

Reversible Inhibitors

  • Blocks cholinergic and nicotinic receptors.
  • Use in the diagnosis and treatment of myasthenia gravis.
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Drugs Affecting the Parasympathetic Nervous System

Irreversible Inhibitors

  • Derivatives of organophosphate compounds.
  • Widely used as insecticides, pesticides and chemical warfare agents.
  • Long duration of action
drugs affecting the parasympathetic nervous system20
Drugs Affecting the Parasympathetic Nervous System

Clinical Use

  • Topical use in glaucoma
  • Treatment of myasthenia gravis
  • Treatment of urinary retention and intestinal stasis
drugs affecting the parasympathetic nervous system21
Drugs Affecting the Parasympathetic Nervous System

Clinical Use

  • Treatment of Alzheimer’s disease.
  • Antidote to skeletal muscle blockers.
  • Antidotes to anticholinergic drug poisoning.
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Drugs Affecting the Parasympathetic Nervous System

Indirect-Acting

Cholinergic Drug

Irreversible

Isoflurophate

Reversible

Ambenonium

Edrophonium

Neostigmine

Physostigmine

Pyridostigmine

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Drugs Affecting the Parasympathetic Nervous System

Adverse and Toxic Effect

  • Nausea
  • Vomiting
  • Diarrhea
  • Blurred vision
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Drugs Affecting the Parasympathetic Nervous System

Adverse and Toxic Effect

  • Excessive sweating
  • Muscular tremors
  • Bronchoconstriction
  • Bradycardia
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Drugs Affecting the Parasympathetic Nervous System

Adverse and Toxic Effect

  • Hypotension
  • Mucular paralysis
  • Respiratory arrest
drugs affecting the parasympathetic nervous system26
Drugs Affecting the Parasympathetic Nervous System

Cholinergic Crisis

  • Excessive drug dosage in patients with myasthenia gravis.
  • High concentration of ACH causes excessive stimulation of the muscarinic receptors.
  • High concentration of ACH causes blockade of nicotinic receptor.
drugs affecting the parasympathetic nervous system27
Drugs Affecting the Parasympathetic Nervous System

Treatment

  • Stop anticholinesterase drug administration.
  • Give atropine to block the effect of excess muscarinic stimulation
drugs affecting the parasympathetic nervous system28
Drugs Affecting the Parasympathetic Nervous System

Cholinergic Crisis

  • Excessive exposure to sprays containing derivatives of irreversible anticholinesterase.
  • High concentration of ACH causes excessive stimulation of the muscarinic receptors.
  • High concentration of ACH causes blockade of nicotinic receptor.
drugs affecting the parasympathetic nervous system29
Drugs Affecting the Parasympathetic Nervous System

Treatment

  • Remove person from the exposure.
  • Give Pralidoxime to reactivate the anticholinesterase enzyme.
  • Give atropine to block the effect of excess muscarinic stimulation
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Drugs Affecting the Parasympathetic Nervous System

Anticholinergic Drugs

  • Binds to muscarinic receptors.
  • Act by competitive antagonism of ACH.
  • Prototype drugs: Belladonna alkaloids, atropine and scopolamine
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Drugs Affecting the Parasympathetic Nervous System

Pharmacological Action

  • Increase heart rate.
  • Increase the secretions of the respiratory tract and may cause bronchoconstriction.
  • Reduce salivary and GI tract.
  • Inhibit urinary peristalsis and voiding of urine.
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Drugs Affecting the Parasympathetic Nervous System

Pharmacological Action

  • Depressant effects on the CNS causing drowsiness and sedation.
  • At high doses cause both stimulation and depression of the CNS
  • At toxic doses excitation, delirium, hallucination and profound CNS depression leading to respiratory arrest and death.
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Drugs Affecting the Parasympathetic Nervous System

Ocular Effect

  • Mydriasis
  • Cycloplegia
  • Increases Intraocular pressure.
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Drugs Affecting the Parasympathetic Nervous System

Adverse and Toxic Effect

  • Cause by excessive blockage of the Parasympathetic Nervous System.
  • Dry mouth.
  • Visual disturbances
  • Urinary retention
  • Constipation.
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Drugs Affecting the Parasympathetic Nervous System

Adverse and Toxic Effect

  • Dryness of the skin
  • Flushing
  • Hyperpyrexia
  • CNS stimulation and depression
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Drugs Affecting the Parasympathetic Nervous System

Anticholinergic Drugs

Semisynthetic Drug

Homatropine

Synthetic Drugs

Diclyclomine

Isopropamide

Propantheline

Methantheline

Belladonna Alkaloids

Atropine

Scopolamine

Hyoscyamine