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Cholinergic Drugs



  1. Directly Acting;



a.  Acetylcholine            
b. Methacholine
c. Carbachol                    
d. Bethanecol

a. Pilocarpine                   
b. Arecholine
c. Lobeline                   
d. Nicotine
e. Muscarine

  1. Indirectly Acting: acts by inhibition of Acetylcholinesterase.

 Two types:  reversible and irreversible

  1. Reversible can be further of two types: Tertiary (lipid soluble) and Quaternary (lipid insoluble)

Tertiary Amines (lipid soluble)

Quaternary Amines (lipid insoluble)

Lipophilic ; crosses BBB, absorbed from git

Hydrophillic; does not cross BBB, GIT

i.   Physiostigmine
ii.  Tacrine
iii. Galantamine
iv. Donepezil
v.  Rivastigmine

i.    Edrophonium                                 
ii.   Neostigmine   
iii.  Ambenonium                 
iv.  Pyridostigmine

  1. irreversible can be further of two types:



1. Malathion             

2. Parathion                              

3. Sulthion

4. Echothiophate   

5. Matrifonate

6. DFP

7. Chlorpyrifos

8. Nerve gas – Tabun, Sarin, Soman


1. Propoxur

2. Carbaryl

3. Aldicarb



  1. Ach is shortest acting drug

    1. T1/2=10-20 seconds                         
    2. Metabolised by Acetylcholinesterase (ACE)
    3. Two Types: True and Pseudo cholinesterase
      Uses: Acetylcholine (MIOCHOL-E) is available as an ophthalmic surgical aid for rapid production of miosis. 
  2. Bethanechol –
    1. Most resistant to hydrolysis, acts on g.i.t and bladder mainly (M-3),
    2. Used in postoperative and postpartum urinary retention and in certain cases of chronic hypotonic, myogenic, or neurogenic bladder.
    3. Adrenergic antagonists are useful adjuncts in reducing outlet resistance of the internal sphincter.
    4. Value in certain cases of postoperative abdominal distention and in gastric atony or gastroparesis.
    5. Prokinetic agents with combined cholinergic-agonist and dopamine-antagonist activity (e.g., metoclopramide) or serotonin-antagonist activity have largely replaced bethanechol in gastroparesis and esophageal reflux disorders.
  3. Carbachol
    1. Direct + indirect (Nico>>musca)   
    2. Also releases stored acetylcholine
    3. Lusitropic (myocardial relaxant effect)               
    4. Maximum hypotension/bradycardia
    5. Do not give by IV injection
  4. Methacholine;
    Methacholine chloride (PROVOCHOLINE) may be administered for diagnosis (provocative test) of bronchial hyperreactivity. Most cardioselective (M-2)
  5. Pilocarpine:
    1. Used in case of Xerostomia assos with Sjogren syndrome.
    2. As ophthalmic solution for MIOSIS.
    3. In open angle glaucoma as Implant (OCUSERT)
      *CEVIMELINE : selective M3 agonist for xerostomia
  6. Arecholine:
    Naturally found in areca nuts (gutka etc)
  7. Muscarine:
    Accidental intake results in poisoning (Mushroom Poisoning)


Symptoms of muscarine intoxication: Salivation, lacrimation, nausea, vomiting, headache, visual disturbances, abdominal colic, diarrhea, bronchospasm, bradycardia, hypotension, shock) develop within 30–60 minutes of ingestion. Treatment with atropine (1–2 mg intramuscularly every 30 minutes) effectively blocks these effects.


  1. Amanita muscaria: Symptoms arises from the neurologic and hallucinogenic properties of muscimol, ibotenic acid, and other isoxazole derivatives that stimulate excitatory and inhibitory amino acid receptors. Symptoms range from irritability, restlessness, ataxia, hallucinations, and delirium to drowsiness and sedation. Treatment is mainly supportive; benzodiazepines are indicated when excitation predominates; atropine often exacerbates the delirium.
  2. Psilocybe and Panaeolus species: Contain psilocybin and related derivatives of tryptamine that cause short-lasting hallucinations. Gyromitra species (false morels) produce GI disorders and a delayed hepatotoxicity. Although fatalities from liver and kidney failure have been reported, they are far less frequent than with amatoxin-containing mushrooms. 
  3. Amanita phalloides, other Amanita species, Lepiota, and Galerina species: These species account for >90% of fatal cases. Ingestion of as little as 50 g of A. phalloides (deadly nightcap) can be fatal. The principal toxins are the amatoxins (a- and b-amanitin), a group of cyclic octapeptides that inhibit RNA polymerase II and hence block messenger RNA (mRNA) synthesis. This causes cell death, particularly in the GI mucosa, liver, and kidneys. Initial symptoms include diarrhea and abdominal cramps. A symptom-free period lasting up to 24 hours is followed by hepatic and renal malfunction. Death occurs in 4–7 days from renal and hepatic failure. Treatment is largely supportive; penicillin, thioctic acid, and silibinin may be effective antidotes.

Acetylcholinesterase Inhibitors (indirectly acting)

  1. Edrophonium
    1. Short acting (half life=10-20 mins)          
    2. Carbamate with alcoholic group      
    3. Nicotinic >> muscarinic

Tensilon Test: Given IV to differentiate between cholinergic weakness from mysthetic weakness (Tensilon test)

Test also positive in Lambert Eaton syndrome           

  1. Neostigmine
    1. Quaternary amine
    2. Ganglion stimulant >>> followed by block
    3. Can exhibit sympathomimetic activity due to ganglion stimulation


DOC;  Cobra bite ,Reversal of neuromuscular block(Not in case of Sch/mivacurium), post op paralytic ileus and post op urinary retention  

  1. Echothiophate

    1. Long acting                      
    2. Half life=100 hours      
    3. Irreversible                  
    4. only irreversible compound used clinically for glaucoma
  2. PHYSIOSTIGMINE: Increases intestinal and bladder motility

a. Reverses CNS and cardiac effects of tricyclic antidepressants

b. Reverses CNS effects of atropine

c. Uncharged, tertiary amine thatcan penetrate the CNS

  1. Pyridostigmine: longest acting, DOC for myasthenia gravis
  2. Tacrine: Used in Alzheimer’s disease but is hepatotoxic
  3. Donepazil (DOC-most selective, longest). Other drugs are rivastigmine, galantamine.  
  4. Galantamine (stimulates both nicotinic & muscarinic receptors)
  5. Memantine (NMDA blocker-advanced disease); useful in advanced Alzheimers disease


Intoxication by anti-ChE agents (Organophosphorous poisoning)

  1. Irreversible AChE inhibitors (mostly organophosphate compounds):
  2. Commonly used as agricultural insecticides, which has led to numerous cases of accidental poisoning with these agents. In addition, they are frequently used for suicidal and homicidal purposes.
  3. Organophosphate nerve gases such as sarin are used as agents of warfare and chemical terrorism.
  4. Toxicity with these agents is manifested as nicotinic and muscarinic signs and symptoms (cholinergic crisis). Depending on the agent, the effects can be peripheral or can affect the whole body.


General measurement: ABC

  1. Atropine in sufficient dosage effectively antagonizes the actions at muscarinic receptor sites, and to a moderate extent, at peripheral ganglionic and central sites. Atropine should be given until muscarinic symptoms disappear, if they reappear, or until signs of atropine toxicity appear.
  2. Atropine is virtually without effect against the peripheral neuromuscular compromise (Nicotinic), which may be reversed by pralidoxime (2-PAM), a cholinesterase reactivator. AChE reactivators are beneficial in the therapy of rganophosphorus anti-ChE intoxication, but their use is supplemental to the administration of atropine.
  3. It is ineffective antidote to carbamate anti-ChEs (physiostigmine neostigmine, carbaryl, propoxur) in which the anionic site of the enzyme is not free to provide attachment to pralidoxime. It is rather contradicated in carbamate poisoning, because it has weak anti-ChE activity of its own.
  4. Other oximes are Obidoxime (more potent than pralidoxime) and Diacetyl-Monoxime (DAM), which is lipophilic and hence cross BBB.


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