cholinergic and anti cholinergic drugs

Nervous system Central nervous system Peripheral nervous system

Autonomic nervous system Somatic nervous system

Sympathetic system Para Sympathetic system

Cholinergic receptors

Muscarinic

Nicotinic

Cholinergic Agents

Anti cholinergic Agents

ClassificationDirect-acting cholinergic agonistsBind to cholinergic receptors located in various tissues and activating them.

Indirect-acting cholinergic agonistsInhibit the enzyme cholinesterase which breaks down acetylcholine these causes an increase in acetylcholine at the receptors

Cholinergic drugs

Direct acting Indirect acting

Direct acting

Muscarinic Nicotinic

Choline esters Alkaloids

Indirect acting

Reversible anticholinesterases

Irreversible anticholinesterases

Classification 1.Esters of choline

2.Cholinomimetic alkaloids

3.Anti cholinesterase

Reversible Irreversible

1.Esters of choline

Acetyl choline.

Bethanechol

Carbachol

2.Cholinomimetic alkaloids

Muscarine Nicotine Pilocarpine

3.Anti cholinesterase

Reversible Physostigmine , Neostigmine , Rivastigmine

Edrophonium. Pyridostigmine

Irreversible Organo phosphorus compounds

Carbamates

Physostigmine Organo phosphorus

compounds

Pyridostigmine

Carbamates

Rivastigmine

Neostigmine

ACTIONS

Heart

It depresses the S A node

reduces the heart rate

Decrease output, lowers BP

Blood vessels

ACh relaxes vascular smooth muscles and dilates blood vessels skin and mucus membranes

Smooth muscles

Ach increases the tone of all other non vascular smooth muscles

Gastro intestinal tract

Increase tone and motility of GI smooth muscles

Increase peristalsis

Urinary bladder

Contraction of the detrusor muscle bladder increase bladder pressure and relaxes trigon and bladder sphincter promotes urination.

Bronchial smooth muscles

Contracts resulting in bronchospasm.

Secretory glands

Enhances the secretions of all glands ; salivary, lacrimal, nasopharyngeal, tracheo bronchial, gastric and intestinal secretions are increased.

Sweating is also increased.

 

Eye

Ach bring about constriction of pupil(miosis) by contracting the circular muscles of the iris.

Neuro muscular junction

Ach brings about contraction of skeletal muscle by stimulating nicotinic receptors.

Ophthalmological Uses

Glaucoma - Carbachol ,Pilocarpine

Miotic in surgery - Acetylcholine and Carbachol

Xerostomia - Pilocarpine

Bethanechol (Urecholine)

GI smooth muscle stimulant - Gastrointestinal atony 

Postoperative abdominal distension

Post-operative paralytic ileus

Indirect acting cholinergic agonists

Anti cholinesterases

Reversible anti cholinesterase

Irreversible anti cholinesterase

Reversible anti cholinesterase

Physostigmine

1.As a miotic – physostigmine causes miosis , spasm of accommodation and a decrease IOP.

Glaucoma – can be used with pilocarpine for better effect.

2. Myasthenia gravis

Chronic auto immune disease characterized by progressive weakness with easy fatiguability of skeletal muscles.Neostigmine (15 mg tab 6 hrly) or pyridostigmine

3.Poisoning due to anticholinergic drugs

Physostigmine is used in atropine poisoning

4.Curare poisoning

Skeletal muscle paralysis cause by curare can be antagonised by AntiChEs

5.Post-operative paralytic ileus and urinary retention Neostigmine may be useful.

6.Cobra bite cobra venom , a neuro toxin causes skeletal muscle paralysis. Intra venous edrophonium prevents respiratory paralysis

 Irreversible anti cholinesterase

Organo phosphorus compounds

Carbamates

Treatment

If poisoning is through skin remove clothing and wash the skin with soap and water; if consumed by oral gastric lavage is given.

2.Drug of choice is atropine I V 2 mg every 10 minutes

3.The antidote of choice is pralidoxime (protopam,PAM).

Anticholinesterase or Organophosphate poisoning

DUMBBELSS

Diarrhea, Urination, Miosis, Bronchospasm, Bradycardia, Excitation of skeletal muscle and CNS, Lacrimation, Sweating, Salivation

ANTICHOLINEGIC DRUGS

CLASSIFICATION

1.Natural alkaloids

2. Semisynthetic derivatives

3.Synthetic substitutes

1.Natural alkaloids

Atropine, hyoscine

2.Semisynthetic derivatives

Homatropine, ipra tropium bromide

3.SYNTHETIC SUBSTITUTES

MydriaticsTropicamide, eucatropine 

Anti-spasmodic ant secretory agents

Dicyclomine,telenzipine, glycopyrrolate

Antiparkinsonian agentsBenztropine, trihexy phenidyl

Actions

 1.CVSIncreases heart rateIn large doses vaso dilation and hypo tension occurs. Lowers HR (in small doses) Increases HR (in large doses)

2.SecretionsAtropine reduces all secretions except milk.Decreased salivation resulting in dry mouth and difficulty in swallowing.

3.Smooth muscleGIT Relaxes smooth muscle of GI tract Decreases intestinal and gastric secretions Decreases motility and peristalsis

Biliary tract

Smooth muscle are relaxed and biliary spasm is relieved.

RespiratoryDecreases bronchial secretions Dilates bronchial airways

 

Urinary bladderRelaxes ureter and urinary bladder and may cause urinary retention. Relaxes detrusor muscle

Uses 1.Anti spasmodic

  2.As a mydriatric and cycloplegic

3. as pre anaesthetic medication

Adverse effects

Blurring of vision, dry mouth, ,dry skin dysphagia, fever constipation and urinary retention. High doses causes palpitation, flushing, restlessness,

delirium, hallucinations, psychosis , convulsions and coma

 anti-SLUD  (Salivation, Lacrimation, Urination, Defecation)

Contraindications

*Drug Allergy *Narrow-angle glaucoma *Acute asthma *Myasthenia gravis *Respiratory distress *Acute cardiovascular instability *GI/GU obstructions