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Cholinoceptor Blocking Agents

Cholinoceptor Blocking Agents. Pawitra Pulbutr M.Sc. In Pharm (Pharmacology). Objectives. นิสิตมีความรู้ความเข้าใจถึงเภสัชวิทยา กลไกการออกฤทธิ์ เภสัชจลนศาสตร์ การใช้ประโยชน์ทางคลินิก อาการไม่พึงประสงค์ ข้อควรระวังการใช้ยาของที่ออกฤทธิ์ต้านโคลิโนเซปเตอร์. Cholinoceptor Blocking Agents.

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Cholinoceptor Blocking Agents

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  1. Cholinoceptor Blocking Agents Pawitra Pulbutr M.Sc. In Pharm (Pharmacology)

  2. Objectives • นิสิตมีความรู้ความเข้าใจถึงเภสัชวิทยา กลไกการออกฤทธิ์ เภสัชจลนศาสตร์ การใช้ประโยชน์ทางคลินิก อาการไม่พึงประสงค์ ข้อควรระวังการใช้ยาของที่ออกฤทธิ์ต้านโคลิโนเซปเตอร์

  3. Cholinoceptor Blocking Agents • Inhibit binding of ACh or cholinoceptor agonist to cholinoceptor • Cholinoceptor antagonist/ blocker • Parasympatholytic … Not appropriate • Antimuscarinic receptor • Antinicotinic receptor • Ganglionic blocker • Neuromuscular blocker

  4. Basic Pharmacology of Muscarinic blocker • Prototype = “Atropine” • Tertiary amine derivative • Quaternary amine derivative … increase peripheral effect • Atropine (Hyoscyamine) • Atropa belladonna (deadly nightshade) • Datura stramonium (jimsonweed or thorn apple) • L (-) hyoscyamine = natural occur • d,l- hyoscyamine = commercial available • Scopolamine (Hyoscine) • Hyoscyamus niger • L (-) hyoscine = natural occur • L-isomer is more active than d-isomer

  5. Organ System Effects • CNS • Atropine • CNS stimulation…also sedative effect • Scopolamine … More CNS effect • Drowsiness, amnesia • Toxic dose … excitement, agitation, hallucination, coma • Use • Tremor in Parkinson’s disease • Overcholinergic activity… Too much ACh • Lack of dopaminergic activity in brain • Antimuscarinic agent + Dopamine precursor • Motion sickness … Vestibular disturbance • Scopolamine

  6. Eyes • Cholinoceptor … Control pupillary contractor muscle & ciliary muscle • Anticholinoceptor • Mydriasis • Inhibit ciliary muscle contraction • Cycloplegia • Focus defect • Use in ophthalmology • Caution in glaucoma… increase intraocular pressure • Decrease lacrimal secretion, sandy eyes

  7. CVS • Atropine at heart • Low dose… Inhibit presynaptic cholinoceptor first … increase ACh release …bradycardia • Moderate to high dose… Relative tachycardia • AV node • (+) dromotropic … Shorten PR interval • Less effect on ventricle • Total effect of Atropine • >>> Modest effect in normal hemodynamic • Tachycardia • Less effect on BP

  8. Respiratory system • Vagal innervation … Smooth muscle & secretory gland • Atropine • Bronchodilation • Decrease secretion • Use • Asthma… less effective than 2-agonist • Chronic Obstruction Pulmonary Disease (COPD) • Premedication of inhalant anesthetic agent… decrease secretion & laryngospasm

  9. GI tract • Decrease GI motility & secretion • Prolong gastric emptying time & intestinal transit time • Partially effect …ENS controlled by local hormone & other noncholinergic neuron • Decrease saliva …dry mouth • Less effect on gastric secretion • Mostly on basal secretion • Pirenzepine, Telezepine… decrease gastric acid secretion • No effect on pancreatic & intestinal secretion … under hormonal control • Use • Peptic ulcer… Not use recently • Control diarrhea from parasympathetic system overactive • Spasmolytic action

  10. Genitourinary tract • Relaxation of ureter & bladder • Decrease voiding • Use …urinary tract spasm… inflammation • Caution in elderly male … BPH>>> urinary retention • No effect on uterus

  11. Sweat gland • Inhibit thermoregulatory sweating • Inhibit eccrine gland secretion • Controlled by cholinergic sympathetic nerve • May cause …Atropine fever

  12. Clinical Pharmacology • Parkinson’s disease • Motion sickness • Mydriasis • Adjunct to general anesthesia • Asthma/ COPD • Hyperactive carotid sinus reflex … fainting • Antispasmodic, traveller diarrhea, peptic ulcer • Urinary urgency • Urolithiasis • Cholinergic poisoning

  13. ADRs of anticholinoceptor • Depends on desired effect • Cholinoceptor blocking effect • Dry mouth, mydriasis, tachycardia, hot flush, agitation, delirium, increase body temperature (esp infant) • Reversal of atropine overdosage • Symptomatic • ACh E inhibitor … physostigmine … ADRs

  14. Contraindication of Atropine • Glaucoma • Angle closure glaucoma • Elderly male • BPH • Peptic ulcer • Decrease gastric emptying

  15. Q & A

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