Drug (examples) MOA, indications and ADRs

  1. acetylcholine esterase inhibitor
    • edrophonium (SA), neostigmine (LA)
    • organophosphates which phosphorylate the acetylcholine esterase enzyme preventing its breakdown, increasing [ACh] in synaptic junction and therefore increasing the EPSP
    • myasthenia gravis (reduced AChRs), antidote for muscle relaxants
    • increased parasympathetic activity e.g. GI disturbances, bronchoconstriction. decreased HR
  2. muscarinic antagonist
    • atropine, ipratropium (bronchodilator with with beta2), scopalamine (motion sickness)
    • competitively bind to muscarinic receptors to prevent binding and depolarisation by ACh, decreasing parasympathetic stimulation
    • decreased GI motility (constipation), secretion (dry mouth), increased HR (tachycardia, palpitations), urine retention
  3. depolarising neuromuscular blockers
    • succinylcholine
    • binds to free closed NMJ nicotinic receptor causing a depolarision but desensitising the receptor to ACh even after repolarisation to prevent further depolarisation by ACh binding, decreasing muslce contraction
    • muscle relaxant pre-op
    • may bind to M receptors as agonist causing parasympathetic disturbances (increased GI secretions, motility; bradycardia), muscle pains, hyperkalemia due to excessive contraction at administration
  4. non-depolarising neuromuscular blocker
    • tubocurarine
    • binds to NMJ nicotinic receptor preventing binding and depolarisation by ACh preventing muscle contraction
    • adjuvant to surgical anaesthesia
    • histamine release causes hypotension and bronchospasm
  5. norepinephrine
    • nonspecific adrenergic agonist which binds to activates both alpha and beta adrenergic receptors
    • however lower affinity for beta 2 meaning its alpha 1 effects are magnified causing vasoconstriction, HTN and reflex bradycardia
    • used for severe hypotension, septic shock
  6. epinephrine
    • nonspecific adrenergic agonist which binds to activate both alpha and beta adrenergic receptors
    • increases HR and decreases BP at low dose, cause HTN at high dose
    • used for cardiogenic shock, cardiac arrest
  7. alpha 1 specific agonist example and indication
    • phenylephrine
    • nasal decongestant
  8. alpha 2 specific agonist (-ADRs)
    • clonidine, alpha methyldopa
    • activate alpha 2 receptors which act in negative feedback, decreasing sympathetic stimulation, therefore actually acting to decrease adrenergic nerve stimulation overall
    • antihypertensive
  9. beta 1 specific agonist (-ADRs)
    • dobutamine
    • increase HR and SV
    • heart failure, cardiogenic shock
  10. beta 2 specific agonist
    • salbutomal, salmeterol (+ fluticasone)
    • increase bronchodilatory action of beta 2 receptors in respiratory SM
    • asthma
    • hypotension with reflex tachycardia, skeletal tremors and hypokalemia (futher increasing HR)
  11. alpha adrenergic blockers
    • prazosin, doxazosin
    • block alpha 1 adrenergic receptors which normally cause vasoconstriction, causing vasodilation and reducing BP
    • antihypertensive
    • few side effects due to specificity
  12. beta adrenergic blockers
    • propanolol (nonselective), metoprolol/atenolol (beta 1 seelctive), carvedilol (beta 1 and 2, alpha 1)
    • block beta 1 and 2 (cause bronchoconstriction as a side effect) adrenergic receptors which normally increase HR/SV, while extra blockade of carvedilol also causes vasodilation for antihypertensive
    • used for range of CVS diseases
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Drug (examples) MOA, indications and ADRs