4.cholinergic and anticholinergics

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  1. 1. Drugs Acting On AutonomicDrugs Acting On Autonomic Nervous System (ANS)Nervous System (ANS)
  2. 2. NeurotransmittersNeurotransmitters Sympathetic: noradrenaline (norepinephrine) Parasympathetic : acetylcholine
  3. 3. Cholinergic receptorsCholinergic receptors Muscarinic: M1 M5 Activated by muscarine Nicotinic: NM, NN Activated by nicotine
  4. 4. Actions of AchActions of Ach Acetylcholine major neurotransmitter of PNS
  5. 5. Actions of Ach Characteristics M1 (neuronal) M2 (cardiac) M3 (glandular) Location & Function Ganglia impulse transmission SA node -Decreased rate of impulse generation AV node decreased conduction velocity Atrium, ventricle- decreased contractility Exocrine glands- secretion Visceral smooth Muscle contraction
  6. 6. Actions of Ach Characteristics M1 (neuronal) M2 (cardiac) M3 (glandular) Location & Function Ganglia impulse transmission SA node -Decreased rate of impulse generation AV node decreased conduction velocity Atrium, ventricle- decreased contractility Exocrine glands- secretion Visceral smooth Muscle contraction
  7. 7. Actions of Ach Characteristics M1 (neuronal) M2 (cardiac) M3 (glandular) Location & Function Ganglia impulse transmission SA node -Decreased rate of impulse generation AV node decreased conduction velocity Atrium, ventricle- decreased contractility Exocrine glands- secretion Visceral smooth Muscle contraction
  8. 8. Actions of Ach Characteristics M1 (neuronal) M2 (cardiac) M3 (glandular) Location & Function Ganglia impulse transmission SA node -Decreased rate of impulse generation AV node decreased conduction velocity Atrium, ventricle- decreased contractility Exocrine glands (salivary, sweat) -secretion Visceral smooth Muscle (bronchus, bladder, GIT) contraction
  9. 9. Actions of Ach Characteristics NM (muscle type) NN (neuronal type) Location & Function Skeletal neuromuscular junction (NMJ) contraction Autonomic ganglia impulse transmission
  10. 10. Actions of ACh on eye Muscarinic: Eye: -Circular muscle of iris (M3)- contraction- miosis -Ciliary muscle (M3) contraction- eyes focus is accomodated for near vision spasm of accomodation -Better drainage of aqueous humor reduced intraocular pressure -Lacrimal glands (M3) - lacrimation
  11. 11. AcetylcholineAcetylcholine No therapeutic use because i) Ultra short action: rapidly hydrolyzed by cholinesterases ii)Widespread and nonselective activity: act on all receptors
  12. 12. Drugs which mimic the actions of Ach are called as cholinergic drugs or parasympathomimetic drugs or cholinomimetic or cholinergic agonists
  13. 13. Classification 1. Directly acting Methacholine, bethanechol, pilocarpine Act on muscarinic receptors
  14. 14. 2. Indirectly acting (Anticholinesterases) A. Reversible : Physostigmine, neostigmine, pyridostigmine, edrophonium B. Irreversible: Organophosphates: Parathion, Malathion
  15. 15. Mechanism of action of Anticholinesterases Inhibit acetylcholinesterase (AChE) enzyme Ach ----------- Choline + acetate AChE Accumulation of Ach Action Neostigmine ___ _
  16. 16. Therapeutic uses Ophthalmic use : i) Glaucoma ii)To counteract the effects of mydriatics iii) To break adhesions between the iris and lens or iris and cornea Myasthenia gravis : neostigmine Belladona (Atropine) poisoning : Physostigmine specific antidote
  17. 17. Irreversible AChE inhibitorsIrreversible AChE inhibitors Mainly used as insecticides and pesticides
  18. 18. Adverse effects ofAdverse effects of anticholinesterasesanticholinesterases Diarrhea, urination, bronchoconstriction, lacrimation, salivation, sweating, bradycardia, fasciculation of skeletal muscle Organophosphorus poisoning: treated with an anticholinergic, atropine
  19. 19. Anticholinergic DrugsAnticholinergic Drugs
  20. 20. Classification Natural alkaloids : Atropine* (prototype), Scopolamine (Hyoscine) Semisynthetic derivatives : Homatropine*, ipratropium bromide, tiotropium bromide Synthetic compounds : i) Mydriatics Cyclopentolate*, tropicamide ii)Antiparkinsonian Benzhexol, Biperiden, Benztropine
  21. 21. iii) Antisecretory- antispasmodics Dicyclomine Pirenzepine Glycopyrrolate Semisynthetic and synthetic anticholinergics - Atropine substitutes
  22. 22. Pharmacological actions of atropinePharmacological actions of atropine CNS : High doses restlessness, delirium, disorientation
  23. 23. CVS : Tachycardia
  24. 24. Eye : mydriasis : Passive mydriasis Photophobia, abolition of light reflex Paralysis of accomodation or cycloplegia Rise in IOP Decrease in lacrimation dry eyes
  25. 25. Respiratory system : Bronchodilatation Decreased secretions GIT : Reduce gastric acid secretion Reduced tone and motility of gut, constriction of sphincters constipation
  26. 26. Genitourinary tract : Relaxation of ureter and urinary bladder urinary retention Glands : Decreases sweat, salivary, tracheobronchial and lacrimal secretion Body temperature : Rise in body temperature Atropine fever
  27. 27. Uses of atropineUses of atropine Preanaesthetic medication: to decrease secretion Oraganophosphorous poisoning
  28. 28. Therapeutic usesTherapeutic uses Motion sickness : Scopolamine Parkinsons disease :benzhexol, benztropine etc. Bronchial asthma : ipratropium and tiotropium bromide Preanaesthetic medication : glycopyrrolate , As mydriatic during fundoscopy and testing of refractive error Tropicamide, cyclopentolate
  29. 29. Side effects of atropine : Dry mouth Blurred vision and photophobia Urinary retention Constipation Dry, hot skin Precipitation of glaucoma Decreased sweating