PHARM: ANS Drugs Flashcards
3 types of B-receptors
- β1: increased HR and contraction force (we have 1 heart)
- β2: bronchodilation, pupil dilation, (we have 2 lungs and eyes), relax GIT and bladder muscle
- β3: lipolysis in adipose tissue, relax GIT and bladder muscle
2 types of a-receptors
- a1: vasodilation to skeletal muscle, contraction of GIT/bladder/bowel sphincters, pupil dilation, constriction of nasal vessels
- a2: noradrenaline -ve feedback (decreased NA) + vasoconstriction
types of M receptors and where are they found?
- M1, M4, M5: mostly CNS
- M2 = heart
- M3 = everywhere else, mostly smooth muscle INC SWEAT GLANDS
structure of nicotinic and muscarinic receptors
- N: pentameric ligand-gated ion channels (Ach leads to opening of ion channels > Na+ influx > depol) - ionotropic = susceptible to depolarising block
- M: G-protein coupled receptors (metabotropic)
adrenaline vs noradrenaline affinity for a/B receptors
- adrenaline: greater affinity for a-receptors
- NA: greater affinity for B-receptors
structure of a/B receptors
- G-protein coupled (metabotropic)
why aren’t there many drugs which block N receptors at the ganglia?
- b/c both sympathetic and parasympathetic ganglia have N receptors
- therefore it will have adverse effects and block both
acronym to think abt effects of parasympathetic NS
- Diarrhoea
- Urination
- Miosis (pupil constriction)
- Bradycardia
- Emesis
- Lacrimation (tears)
- Lethargy
- Salivation
what is anticholinergic syndrome and what is the Tx?
- decreased response to Ach
- Tx: physostigmine (AChE inhibitor)
ophthalmologic uses of muscarinic antagonists and agonists
- agonists (e.g. pilocarpine) = contract iris and ciliary muscles = outflow of aqueous humour to reduce pressure + treat glaucoma
- antagonists (e.g. atropine) = pupil dilation for eye exam
respiratory uses of muscarinic antagonists
- ipratropium = bronchodilator for asthma and COPD
- atropine used before surgery to reduce lung secretions prior to anaesthesia
GI uses of muscarinic antagonists and agonists
- agonist (e.g. bethanechol) stimulates GI motility
- antagonist (e.g. hyoscine) decreases GI motility so used for GI cramping + diarrhoea
CNS uses of muscarinic antagonists + agonists
- agonists (e.g. pilocarpine): limited use but potential to increase cognitive function in alzheimer’s
- antagonists: hyoscine prevents motion sickness and benzatropine counteracts movement disorders in Parkinson’s
describe the potency of noradrenaline, adrenaline and isoprenaline for a and B receptors
- a: noradrenaline > adrenaline > isoprenaline
- B: isoprenaline > adrenaline > noradrenaline
use of adrenoreceptors in the eye
- a1 agonists (e.g. phenylephrine): pupil dilation
- B2 antagonists (e.g. timolol): reduce aqueous humour formation to decrease pressure > treat glaucoma
use of adrenoreceptors in the heart
- B1 agonist (dobutamine): increase contractility for ACUTE heart failure
- B2 antagonist (atenolol): decrease contractility for HFrEF, also anti-HTN
use of adrenoreceptors in lungs
- B2 agonists: bronchodilation (salbutamol most common, eformoterol longer lasting)
- B antagonists: contraindicated in asthmatics b/c may result in bronchospasm
phentolamine MOA
- a1 antagonist: lowers BP thru vasodilation
- also a2 antagonist: reduced NA -ve feedback = increased NA = tachycardia
pyridostigmine
- class
- MOA
- AChE inhibitor
- reversibly binds to acetylcholinesterase to slow ACh breakdown > increased parasympathetic
pralidoxime
- class
- MOA
- antidote
- reactivates AChE if it has been impaired after organophosphate poisoning to decrease [ACh]
atropine
- class
- MOA
- antimuscarinic
- reversibly binds to M receptors which prevents ACh from binding = increase in sympathetic
rocuronium
- class
- MOA
- muscle relaxant (non-depolarising blocker)
- competitive antagonist @ N receptors > overcome by increasing [Ach]
suxamethonium
- class
- MOA
- muscle relaxant (depolarising blocker)
- agonist @ N receptors > keep in depolarised state instead of allowing for depol/repol cycle which is needed for contraction
- inactivate Na+ channel > receptors unresponsive to Ach
- action made worse by increasing Ach
benztropine
- class
- MOA
- antimuscarinic
- corrects imbalance of dopamine and ACh which is seen in ppl w/ Parkinson’s
hyoscine
- class
- MOA
- antimuscarinic (GIT)
- acts on emesis centre in brain = useful for motion sickness
ipratropium
- class
- MOA
- antimuscarinic (respiratory)
- causes bronchodilation and decreased mucous secretions (useful for COPD and asthma)
oxybutynin
- class
- MOA
- antimuscarinic (urinary)
- relaxes smooth muscle in bladder and hence relieves urinary incontinence
prazosin
- class
- MOA
- alpha blocker (a1)
- antihypertensive and improves urinary flow
tamsulosin
- class
- MOA
- alpha antagonist (a1)
- uroselective: relaxes smooth muscle in bladder + prostate
clonidine
- class
- MOA
- a2 agonist
- decreases NA release = decreased sympathetic effects
levodopa
- class
- MOA
- what drug is it often combined with?
- decarboxylase inhibitor
- restores dopamine lvls in Parkinson’s
- often combined w/ carbidopa
