3.cholinergic drugs


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Third Year

Published in: Health & Medicine

3.cholinergic drugs

  1. 1. Introduction Organization of the nervous system Lippincott’s pharmacology 4th edition
  2. 2. Drugs Act on Autonomic nervous system Drugs that produce Parasympathetic like actions = Parasympathomimetics = Cholinergics  Drugs that oppose Parasympathetic = Parasympatholytic = Anticholinergics Drugs that produce sympathetic like action = Sympathomimetics = Adrenergics  Drugs that oppose sympathetic = Sympatholytics = Antiadrenergics
  3. 3. Cholinergic transmission Lippincott’s pharmacology 4th edition
  4. 4. Cholinoceptors • Muscarinic receptors: 3 subtypes are well defined pharmalogically M1, M2 M3 found on ganglia of the peripheral nervous system and on the autonomic effector organs, such as the heart, smooth muscle, brain, and exocrine glands • Nicotinic receptors (N) present in autonomic ganglia adrenal medulla neuromuscular junction
  5. 5. Drugs that stimulate muscarinic receptors Direct Parasympathomimetics Indirect Parasympathomimetics (Anti-cholinesterases) Direct Parasympathomimetics: They stimulate the muscarinic receptors directly. Indirect Parasympathomimetics (Anti-cholinesterases): They inhibit cholinesterase enzyme leading to accumulation of endogenous acetylcholine at both muscarinic and nicotinic receptors Mechanism of action
  6. 6. Pharmacological actions of Cholinergics Effector organs Effects Eye Myosis Accommodation Reduction of intraocular pressure (IOP) Increase lacrymation. Heart ↓ heart rate ↓ force of contraction Slow conduction Blood vessels Constriction of coronary arteries Stomach and Intestine ↑ motility and secretion Urinary bladder Relaxation of sphincters and contraction of bladder wall Respiratory system Constriction of bronchi increased bronchial secretions Exocriene glands Stimulate all e.g. sweating, salivation and lacrymation.
  7. 7. Direct cholinergic agentsAcetyl-choline is It is a natural direct parasympathomimetic. stimulates directly both muscarinic & nicotinic receptors important physiologically, it is not used clinically because its actions are very brief because of rapid hydrolysis Methacholine more selective on cardiovascular system .Weak nicotinic effect. Carbachol : has muscarinic and nicotinic but it is mainly selective on EYE, gastrointestinal tract and urinary tract Bethanichol Actions: No nicotinic action, but only muscarinic action which is mainly selective on gastrointestinal tract , and urinary system. Pilocarpine Direct muscarinic agonist specific on eye and secretions . Very weak nicotinic action
  8. 8. Reversible anticholinesterases Physostigmine has muscarinic action most specific on eye and CNS stimulation Neostigmine It produces both nicotinic and muscarinic actions but it is more active on the nicotinic receptors of the N-M junction. Its muscarinic actions are more specific on the gastrointestinal and urinary tracts. No CNS action
  9. 9. Generic name Indication Methacholine paroxysmal atrial tachycardia and peripheral vascular disease Carbachol Glucoma Post-operative paralytic ileus Post- operative retention of urine Bethanechol Post-operative paralytic ileus Post- operative retention of urine Pilocarpine Glucoma physostigmine Glucoma Anti-cholinergic poisoning Neostigmin Myasthenia gravis Reversal of neuromuscular blockade Urine retention Cholinergic agents indications
  10. 10. cholinergic agents Adverse effects • Muscarinic: ◆ Miosis, lacrymation, salivation, sweating ◆ Urgency and spontaneous micturition ◆ Bronchospasm and increased bronchial secretion. ◆ Bradycardia and hypotension. ◆ Colic, vomiting, diarrhea, hyperacidity & peptic ulcer • Nicotinic: skeletal muscle twitches followed by paralysis Contraindication • Bronchial asthma • Peptic ulcer • Coronary insufficiency • Thyrotoxicosis • Mechanical obstruction of the GIT and urinary bladder