Cholinergic drugs

Cholinergic drugs:

drugs, which act on acetylcholine receptors and evoke response similar to those, produced by acetylcholine and to those,which result from cholinergic nerve stimulation,are called cholinergic drugs.

           Cholinergic drugs

Classification of cholinergic drugs

 Direct acting

1.Choline esters:

•   Acetylcholine 
•   Methacholine
•   Carbachol
•   Bethanechol

2.Natural cholinomimetic alkaloids:

•   Pilocarpine
•   Arecoline
•   Muscarine
•   Nicotine

Indirect acting

1.Reversible:

•   physostigmine
•   Neostigmine
•   Pyridostigmine
•   Endrophonium

2.Irreversible 

  a) Alkyl-phosphate group:

•     TEPP(tetra-ethyl pyro-phosphate)
•     HETP(hexa-ethyl tetra-phosphate)
•     DFP(di-isopropyl fluro-phosphate)
•     OMPA(octa methyl pyrophosphor amide)

  b) Aryl group:

•     Chlorothion
•     Malathion
•     Parathion
•     Diazinon

Clinical uses of cholinergic drugs (or muscarinic agonist )

1.  Treatment of glaucoma(Pilocarpine eye drop)
2.  Urinary bladder atony(Carbachol)
3.  Supraventricular tachycardia(Methacholine)
4.  Cerebrospinal disease( Arecoline)
5.  After bowel surgery(to prevent paralytic ileus) 

contraindication of cholinergic drugs

1.  Bronchial asthma.
2.  Peptic ulcer disease.
3. Myocardial infarction.
4. Hyperthyroidism
5. Obstructive urinary retention.

Adverse effects of cholinergic drugs

Mild:

•     Lacrimation
•     Salivation
•     Bradycardia

severe

•     Hypotension
•     Bronchospasm
•     cardiac arrhythmia

Individual cholinergic drugs

Acetylcholine

Acetylcholine is an organic chemical that works in the brain and body of a variety of animals, including humans-

As a neurotransmitter - a chemical message issued to send the cells signals to other cells through a neural message [neurons, muscles Cells and gland cells]

Pharmacological action of Acetylcholine:

muscarinic action:

1.On cardiac muscle;
Depress the cardiac muscle by stimulating vagus nerve and produce-

• "-ve" inotropic action : Decrease force of contraction.
• "-ve" chronotropic action : Decrease heart rate.
• "-ve" bathmotropic action :Decrease conductivity.
• "-ve" dromotropic action :Decrease automaticity.
• Decrease stroke volume and cardiac output

                              (the net effect :fall of blood pressure)

2.On smooth muscle:

Contraction of smooth muscles except vascular and aphincteric smooth muscle.

On Eye:

•  Miosis (due to constriction of circular muscle)
•  Accommodation for near vision(due to contraction of ciliary muscle)
•  Decrease intraocular pressure.
•  Increase lacrimal secretion (tear).

On lung:

•  Bronchoconstriction
•  Increase bronchial secretion

On GIT:

• Increase HCL secretion
• Increase intestinal secretions
• Increase motility

Nicotinic action:

On autonomic ganglia:
  CVS action:

•  Tachycardia
•  Increase blood pressure

  
 GIT action:

• Increase motility
• Increase secretion

 CNS action:

• Excitation followed by depression
• Anxiety
• Restlessness
• Insomnia

Pilocarpine

• Pilocarpine is an alkaloid obtained from the leaf of "Pilocarpus jaborandi". It shows only muscarinic action and its action can be blocked by atropine.

Pharmacological action of Pilocarpine

On CVS:

• Negative inotropic action
• Negative chronotropic action

On blood vessels:

• Vasodilatation

On Lung:

•  Bronchoconstriction
•  Increase bronchial secretion

On GI trac:

•  Increase salivation
•  Increase GIT secretions
•  Increase motility of gut
•  Sphincter relaxation

On Urinary bladder:

• constraction of detrusor muscle

On Exocrine glands:

• Lacrimation
• Salivation 
• Sweating

On Eye:

• Miosis

Indication of Pilocarpine

• Treatment of glaucoma along with anti-cholinesterase
• As miotics 
• Urinary bladder atony
• Atropine fever

adverse effects of Pilocarpine

• Nausea
• Vomitine
• Diarrhoea
• Salivation 
• Sweating 
• Bronchospasm
• Cutaneous vasodilatation

Physostigmine 

• Alkaloid in nature (source:calabar bean).
• Tertiary amine compound-so can enter into the CNS.
• Orally active 
• Main action on the eyes and CNS
• Eye: Miosis:Constraction of pupil.

Therapeutic uses:

•  Treatment of glucoma 
•  Atropine poisoning