Anticholinergics (VK)

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  • 1. Anticholinergics
  • 2. Anticholinergics   Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS) i.e. on muscarinic receptors: Autonomic effectors CNS Nicotinic antagonists also block certain actions of Ach, they are generally referred to as- Ganglionic blockers / NMBs
  • 3. Cholinergic Blocking Agents: Mechanism of Action    Competitive antagonists Compete with ACh Block ACh at the muscarinic receptors in the PSNS  As a result, ACh is unable to bind to the receptor site and cause a cholinergic effect.
  • 4. Classification  Natural: Atropine, Hyoscine (Scopolamine)  Semisynthetic: Homatropine Atropine methonitrate Ipratropium bromide Hyoscine butylbromide
  • 5.  Synthetic: a) Mydriatics: Cyclopentonate, Tropicamide b) Antisecretory antispasmodic: I) Quaternary compounds: Propantheline, Clidinium, Oxyphenonium, Pipenzolate methyl bromide, Glycopyrolate. II) Tertiary compounds: Dicyclomine, Pirenzepine c) Vasicoselective: Oxybutinin, Flavoxate, Tolterodine d) Antiparkinsonian: Trihexyphenidyl, Biperidin.
  • 6. Pharmacological actions Atropine as prototype  CNS Overall CNS stimulant effect  Small doses: These effects are not appericiable, decrease muscle rigidity and tremors  Large doses: stimulates medullary centres- vagal , respiratory, vasomotor centres    drowsiness, disorientation, hallucinations –(cortical excitation) Depresses vestibular excitation- antimotion sickness property.
  • 7.  Cardiovascular Small doses: decrease heart rate  Large doses: increase heart rate, facilitates AV conduction.  No considerable effect on BP   Eye Dilated pupils (mydriasis)  Decreased accommodation due to paralysis of ciliary muscles (cycloplegia lasting for 7-10 days)  This results into long lasting blurring of vision and photophobia   Body temperature   Rise in body temp.high doses Local anaesthetic
  • 8.  Gastrointestinal     Relax smooth muscle tone of GI tract Decrease intestinal and gastric secretions Decrease motility and peristalsis Genitourinary   Increased constriction of internal sphincter   Relaxed detrusor muscle Result: urinary retention Glandular   Decreased bronchial secretions, salivation, sweating Respiratory  Decreased bronchial secretions  Dilated bronchial airways
  • 9. Atropine substitutes Quaternary compounds  Hyoscine butyl bromide- 20-40mg oral, i.m., Use- oesophageal, Gi spastic conditions.  Atropine methonitrate-2.5-10mg orally, im Use-abdominal colic, hyperacidity  Ipratropium bromide-40-80microgram inhalational Use-COPD, Bronchial asthma
  • 10. Quaternary compounds  Glycopyrrolate: 0.1-0.3 mg im,1-2 mg oral No central effect  Potent and rapidly acting antimuscarinic  Use- For preanaesthetic medication and during anaesthesia   Propanthelin, Clidinium, OxyphenoniumUse- peptic ulcer , gastritis, irritable bowel syndrome, colic, gi hypermotility
  • 11. Tertiary amines  Dicyclomine :20mg oral/im Direct smooth muscle relaxant action  Antispasmodic action  Antiemetic  Use: Dysmenorrhea, irritable bowel syndrome, motion sickness, morning sickness.   Pirenzepine :Use-relief of peptic ulcer pain
  • 12. Vasicoselective drugs  Oxybutinin High affinity for receptors of urinary bladder, and salivary glands  Uses : Neurogenic bladder  spina bifida nocturnal enuresis overactive bladder-urinary urgency, frequency, dysuria
  • 13.  Atropine    Potent Slow & Longer acting Undesirable for refraction tesing    10 times less potent than atropine Dilatation takes 45-60mins last for 1-3 days Cyclopentonate     Pupils dilates in 30-40mins,cycloplegia in 1-3 hrs last for a week Homatropine   Mydriatics Potent and fast acting (dilatation 30-60mins and last for 1day) Preffered for cycloplegic refraction, uveitis, iritis Adverse effects-transient behavioral abnormalities Tropicamide   Quickest (onset-20-40mins , brief duration for 3-6 hrs) Satisfactory for refraction testing in adults and for fundoscopy
  • 14. Uses  As antisecretory Preanaesthetic medication-(Atropine, glycopyrolate, hyosine)  Peptic ulcers  Pulmonary embolism  To check sweating , salivation in parkinsonism   As antispasmodic Intestinal, biliary, renal colic, abdominal cramps  Nervous , functional diarrheoa  Irritable bowel syndrome, spastic constpation  Pylorospasm, gastric hypermotility, gastritis, gastric dyspepsia  Urinary frequency, urgency, enuresis in children  dysmenorrhea 
  • 15.   Bronchial asthma, COPD As mydriatic and cycloplegic    As cardiac vagolytic    Diagnostic therapeutic In partial AV block AMI, digitalis toxicity For central action    Motion sickness Antiparkinsonian OPPs
  • 16. Cholinergic Blocking Agents: Therapeutic Uses CNS Decreased muscle rigidity and muscle tremors  Parkinson’s disease  Drug-induced extrapyramidal reactions
  • 17. Cholinergic Blocking Agents: Therapeutic Uses Cardiovascular Affect the heart’s conduction system   Low doses: slow the heart rate High doses: block inhibitory vagal effects on the SA and AV node pacemaker cells  Result: increased heart rate
  • 18. Cholinergic Blocking Agents: Therapeutic Uses Atropine Used primarily for cardiovascular disorders    Sinus node dysfunction Symptomatic second-degree heart block Sinus bradycardia with hemodynamic compromise (advanced life support)
  • 19. Cholinergic Blocking Agents: Therapeutic Uses Respiratory Blocking the cholinergic stimulation of the PSNS allows unopposed action of the SNS.  Results:  Decreased secretions from nose, mouth, pharynx, bronchi  Relaxed smooth muscles in bronchi and bronchioles  Decreased airway resistance 
  • 20. Cholinergic Blocking Agents: Therapeutic Uses Respiratory agents are used to treat:     Exercise-induced bronchospasms Chronic bronchitis Asthma Chronic obstructive pulmonary disease
  • 21. Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal PSNS controls gastric secretions and smooth muscles that produce gastric motility.  Blockade of PSNS results in:  Decreased secretions  Relaxation of smooth muscle  Decreased GI motility and peristalsis
  • 22. Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal agents are used to treat:    Peptic ulcer disease Irritable bowel disease GI hypersecretory states
  • 23. Cholinergic Blocking Agents: Therapeutic Uses Genitourinary     Relaxed detrusor muscles of the bladder Increased constriction of the internal sphincter Reflex neurogenic bladder Incontinence
  • 24. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Cardiovascular Increased heart rate, dysrhythmias CNS CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium
  • 25. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Eye Dilated pupils, decreased visual accommodation, increased intraocular pressure Gastrointestinal Decreased salivation, decreased gastric secretions, decreased motility
  • 26. Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Genitourinary Urinary retention Glandular Decreased sweating Respiratory Decreased bronchial secretions