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Anticholinergic Drugs



  1. Natural alkaloids - Atropine, Hyoscine (Scopolamine).
  2. Semisynthetic derivatives -  Homatropine, Atropine methonitrate, Hyoscine butylbromide, Ipratropium bromide, Tiotropium bromide.
  3. Synthetic compounds
    1. Mydriatics - Cyclopentolate, Tropicamide
    2. Antisecretory - antispasmodics:
      1. Quaternary amines - Propantheline, Oxyphenonium, Clidinium, Isopropamide, Glycopyrrolate.
      2. Tertiary amlnes - Dicyclomine, Valethamate. Pirenzepine.
    3. Vasicoselective (Bladder): Oxybutynin, Flavoxate, Fesoterodine, Tolterodine, Drotaverine, Darefenacin, Solifenacin
    4. Antiparkinsonian: Trihexyphenidyl(Benzhexol), Procyclidine, Biperiden


Atropine is prototype

  1. Atropine is a tertiary amine                          
  2. Competitive antagonist of MUSCARINIC RECEPTORS
  3. Affects nicotinic receptors in high dose          
  4. Balladona alkaloid
  5. Lipid soluble                                                        
  6. Even skin can absorb it


  1. Atropine is 100% absorbed
  2. Half of atropine is metabolised; rest is eliminated unchanged (glucoronidation)
  3. In normal therapeutic dose, the drug does not enter blood brain or blood placental barrier

Atropine Actions:-

  1. Brain
    1. Sedation                  
    2. Amnesia              
    3. Antimotion sickness (Scopolamine is most potent)
    4. Atropine is oldest antirigidity drug; trihexyphenidyl is more potent & more selective
    5. Transient bradycardia                                                                              
    6. In overdose, stimulation followed by depressin (respiratory depression)
  2. Eye
    1. Mydriasis          
    2. Cycloplegia          
    3. Paralysis of accomodation
    4. Photophobia                              
    5. Dry eyes (sandy eyes)
    6. Used as a cosmetic in renaissance period “belladona” (beautiful lady)
    7. Decreases aqueous outflow-increases IOP
  3. Salivary glands
    1. Dry mouth (0.5 mg)
    2. MC side effect of atropine in adults; in children; MC side effect is hyperthermia
    3. At 10 mg atropine has total antivagal property
  4. Bronchi
    1. Atropine is oldest bronchodilator
    2. Ipratropium & tiotropium are more potent, more selective, longer acting
    3. Ipratropim is the DOC                          
    4. COPD                  
    5. Asthma in diabetics
    6. Used both in acute & chronic asthma              
    7. S/e-dry mouth-fungal sore throat-nystatin gargles
  5. Heart
    1. Antagonises AV block produced by Ach
    2. Increases HR
    3. Bradycardia precedes tachycardia
    4. Brady occurs due to M2 receptor block in presynaptic neurons
    5. RR interval, PR interval-less
  6. Stomach
    1. Decreases volume of gastric juice (least sensitive secretion)
    2. Pirenzepine, telenzepine are used as antisecretary drugs
    3. More selective, & longer acting than atropine
    4. Volume becomes less, pH is unaffacted
    5. Pirenzepine is a tertiary amine
  7. Intestines
    1. Decreases tone, amplitutde, frequency          
    2. Antispasmodic, antidiarroheal

As Antispasmodic agents Synthetic drugs are more potent, selective:-

  1. Flevoxate is selective for ureters; ureteric colic, dysuria, bladder colic
  2. Dicyclomine, antiemetic & antispasmodic-used in dysmennorea-DOC for dysmen-NSAIDS
  3. Pipenzolate use-infantile colic
  1. Bladder
    1. Reduces intravesical pressure
    2. Increase bladder storage capacity
    3. Tolterodine (M3) is most selective for urinary bladder

DOC-irritable bladder syndrome

  1. Oxybutynin is least selective for bladder-hence causes lots of anticholinergic symptoms
  2. Still it is most commonly used drug for urge incontinence and considered as DOC.

Atropine uses


  1. Mushroom poisoning-amanita muscaria            
  2. Organophosphate poisoning
  3. Sinus bradycardia                                      
  4. Sick sinus syndrome
  5. Nerve gas poisoning                                
  6. Mydriasis & cycloplegia (works for 7-10 days)
    Atropine produces both mydriasis & cycloplegia-for routine fundal examination
    Others mydriatic:-
    1. Homtropine-24 hour
    2. Cyclopentolate-1-3 days   
    3. Tropicamide-6 hours (shortest acting)
    4. Atropine is not used in adults, due to long duration of action
    5. It should be used as an ointment

Organophosphate poisoning

  1. Oximes are antidotes                                       
  2. Give them with in 24 hours  
  3. Pralidoxime is peripheral, obidoxime is central                 
  4. Ineffective in carbamate poisoning
  5. DOC for carbamate poisoning-atropine





Atropa belladonna, Datura stramonium

Hyoscyamus niger

ACT mainly on

Heart , bronchus, intestine

eye, secreatory glands


Long acting

Short acting






Depressant, excitatory at high doses.


Poisoning By Antimuscarinic Agents

  1. The deliberate or accidental ingestion of natural belladonna
  2. H1-receptor antagonists
  3. Phenothiazines
  4. Tricyclic antidepressants: protriptyline and amitriptyline


  • Dry mouth, difficulty in swallowing and talking.
  • Dry, flushed and hot skin (especially over face and neck), fever, difficulty in micturition, decreased bowel sounds, a scarlet rash may appear.
  • Dilated pupil, photophobia, blurring of near vision, palpitation.
  • Excitement, psychotic behavior, ataxia, delirium, dreadful visual hallucinations.
  • Hypotension, weak and rapid pulse, cardiovascular collapse with respiratory depression.


  • Physostigmine 1-3 mg s.c. or i.v. antagonizes both central and peripheral effects, but has been found to produce hypotension and arrhythmias in some cases. As such, its utility is controversial.
  • Neostigmine does not antagonise the central effects hence contraindicated.


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