Cholinergic And Anticholinergic Drugs Flashcards
Cholinergic agonists types
- Direct-acting cholinoreceptor stimulants
* Indirect-acting cholinomimetics (inhibit destruction of ACh)
Direct-acting cholinomimetic agonists
- Cholinesters
* Cholinergic alkaloids
Cholinesters examples
ACh, methacholine, carbachol, betachol
Cholinergic alkaloids
Pilocarpine, arecoline, muscadine
Cholinesters therapeutic uses
- GI disorders: Bethanechol for paralytic ileus, congenital megacolon
- Urinary bladder disorders - neurogenic bladder
Alkaloid therapeutic uses
- Xerostomia: orally for Sjögrand’s and head and neck radiation
- Glaucoma: decrease IOP
Cholinergic agonists adverse effects
- Abdominal cramps, belching
- Flushing, syncope, sweating
- Bronchospasm
- Hypotension, bradycardia, heart block
Cholinergic agonists contraindications
- Asthma
- Hyperthyroidism
- Coronary insufficiency
- Peptic ulcer
Mushroom poisoning sources
- Inocybe, clitocybe: muscarine
* Amanita Muscaria: muscimol, ibotenic acid
Mushroom poisoning symptoms
- Salivation
- Lacrimation
- Vomiting
- Headache
- Colic
- Diarrhoea
- Bronchospasm
- Hypotension
- Shock
MOA of anti-cholinesterases
Anti-ChE agents cause accumulation of ACh at ALL sites of Cholinergic transmission
Myasthenia Gravis medication
- Edrophonium: for diagnosis
- Pyridostigmine: longer acting, preferred in patients whose muscles are weak on wakening
- Neostigmine: poorly absorbed, lasts 4h, no CNS action, atropine given tgt
- Distigmine: longest acting (SE: Cholinergic crisis)
Alzheimer’s disease medication
- Tacrine
- Donepezil
- Rivastigmine
Intoxication by anticholinergic drugs medication
• Physostigmine
Reversal of non-depolarising NMB in anaesthesia
• Physostigmine
Acute glaucoma medication
- Pilocarpine
* Physostigmine
Adverse effects of anti-cholinesterases
- Increased muscarinic effects
- Depolarising block
- Cholinergic crisis
- CNS: stimulation followed by inhibition (confusion, drowsiness, convulsion, coma)
Treatment of anti-ChE poisoning (organophosphate insecticide
- Termination of exposure, removal of clothing, washing contaminated skin, gastric lavage
- Maintenance of patient airway
- Control of muscarinic effects: atropine
- Cholinesterase reactivators: oximes
- Supportive measures: oxygen
Atropine dosage
- initial 2-4mg, repeated every 5 mins
- May need 100 ampoules
- Maintained for >72hours
Pralidoxime (PAM)
- 1-2g IV over 5 mins, may repeat after 1 hour
- Drug will reactive AChE enzyme, hasten recovery (most marked in NMJ)
- Metabolised in liver, excreted in urine
- Diacetyl monoxime (DAM) is an alternative
Anticholinergic drugs classification
Muscarinic antagonist
Nicotinic antagonist
Muscarinic antagonist classification
- Natural alkaloids
* Synthetic derivatives
Nicotinic antagonists classification
- Neuro-muscular blockers
* Ganglion blocking agents
Anti-muscarinic alkaloids
- Atropine
* Scopolamine
Muscarinic antagonists synthetic derivatives
- Homatropine
* Ipratropium
Nicotinic antagonists NMB examples
- Tubocurarine
* Vecuronium
Nicotinic antagonists ganglion blocking agents examples
- Mecamylamine
* Trimethaptan
Source of anti-muscarinic alkaloids
- Atropine: Atropa belladonna, Datura stramonium
* Scopolamine: Hyocyamus niger
MOA of anti-muscarinics
- Compete with ACh for common binding site on muscarinic receptors, prevent muscarinic actions
- No blockade of Nicotinic receptors
- Atropine: little CNS action, Scopolamine: marked central effects
Effect of anti-muscarinics on CVS
- Tachycardia: increased HR
- No change to BP
- Treatment of bradycardia due to MI or organophosphate poisoning
- SE: palpitation
Effect of anti-muscarinics on eye
• Action: mydriasis, cycloplegia
• Uses: thorough examination of retina, optic disc
Therapy of iridocyclitis, keratitis
Alternated with miotics for breaking and preventing development of adhesion btwn iris and lens
• SE: photophobia, blurred vision, precipitation of glaucoma
Effect of anti-muscarinics on GIT
- Decreased salivary secretion (treat sialorrhoea) (M3)
- Decreased gastric secretion (M1), mucin, proteolytic enzyme secretion
- useful for pre-anaesthetic medication, treatment of diarrhoea, acute pancreatitis
Effect of anti-muscarinics on GI motility
• Action: prolonged inhibition of motility in stomach, duodenum, jejunum, ileum, colon
reduced tone and amplitude of contractions
• Uses: intestinal colic, diarrhoea, IBS, diverticulitis
Facilitate endoscopy, GI radiology
• SE: constipation
Effect of anti-muscarinics on respiratory tract
- Action: Decreased secretion in both upper and lower respiratory tract
- Uses: relieve acute rhinitis (coryza or hay fever), relax bronchial smooth muscle (bronchial asthma, COPD) (Ipratropium)
- SE: viscid material hard to remove, can block airway, predispose to infection
Effect of anti-muscarinics on respiratory tract (smooth muscle contraction)
- Action: Inhibit smooth muscle contraction in larynx and bronchioles
- Uses: prevent laryngospasm and bronchospasm in anaesthesia
Effect of anti-muscarinics on Genito-urinary tract
- Action: Relax smooth muscle contraction
- Uses: renal colic (opioids), biliary colic, ureteric colic, enuresis in children (tolterodine), reduce urinary frequency in spastic paraplegia
- SE: urinary retention
Atropine in CNS
- Benztropine, benzhexol: control of tremor in Parkinsonism
- Scopolamine: prevention of motion sickness
- SE: dizziness, light-headedness, fatigue
Atropine other uses
- Treatment of mushroom poisoning, organophosphate insecticide poisoning, exposure to chemical warfare agents (sarin)
- Myasthenia Gravis: used with Neostigmine
Ganglion stimulating agents
- Nicotine, Lobeline, TMA
* Stimulates CNS
Ganglion blocking agents examples
- Hexamethonium
- Mecamylamine
- Trimethaphan
Ganglion blocking agents effects
- Blockade of sympathetic ganglia (vasodilation, hypotension, venous pooling, decreased cardiac output)
- Blockade of parasympathetic ganglia (atropine like effects on heart, eye, urinary bladder, salivary glands)
Ganglion blocking agents therapeutic uses
- Acute hypertensive crisis
* Autonomic hyperreflexia
Pyridostigmine use
Myasthenia gravis
Succinylcholine use
Neuromuscular block (eg. tracheal intubation)
Pilocarpine use
Acute narrow angle glaucoma
Atropine use
Pre-anaesthetic medication, organophosphate insecticide poisoning, mushroom poisoning, eye examination
Benztropine use
Parkinsonism
Scopolamine use
Motion sickness
Tubocurarine use
NMB (Nicotinic block)