SNS drugs Flashcards
Adrenaline: describe its selectivity. Give 4 reasons why it treats anaphylactic shock. How does it work in glaucoma? Describe 4 other clinical uses of adrenaline.
Non-selective. Causes bronchodilation, tachycardia, vasoconstriction and supresses mast cell mediator release. In glaucoma, it stimulates a1 recpetors to cause vasconstriction of blood vessels in the ciliary body. Also used to treat asthma (bronchodilation, B2), cardiogenic shock (positive inotropic actions via B1), with spinal anaesthesia (maintains BP) and with local anaesthesia (prolongs duration of action via a1 vasoconstriction).
Name 4 unwanted effects of adrenaline.
Reduced and thickened mucus, tachycardia, arrythmias, hypertension, pulmonary oedema, tremor.
Phenylephrine- describe its selectivity and degradation. Name 3 uses.
Selective for a1. Resistant to COMT but not MAO. Used for vasoconstriction, mydriasis and as a nasal decongestant.
Clonidine- describe its selectivity. Describe 2 clinical uses.
Selective for a2. Hypertension and migraine.
Isoprenaline- describe its selectivity and breakdown. Half-life and significance. 3 clinical uses. One common unwanted effect.
Selective for B1=B2. Resistant to MAO and uptake-1 protein so has a much longer half life than adrenaline of 2 hours. Used for cardiogic shock, acute heart failure and myocardial infarction. Reflex tachycardia via baroreceptors.
Dobutamine- describe selectivity. Breakdown. Clinical use and advantage.
Selectivity for B1. Rapidly metabolized by COMT so plasma half life only 2 minutes. Used to treat cardiogenic shcok and doesn’t usually cause reflex tachycardia (less b2 mediated vasodilation)
Salbutamol- describe selectivity and breakdown. Two clinical uses and two unwanted effects.
Selectivity for B2 (ventolin) and relative resistance to COMT and MAO. Used to treat asthma and threatened premature labour. Can cause reflex tachycardia, blood sugar dysregulation and tremor.
What can cocaine be described as? How does it work? What effects does it have at low and high doses?
An indirectly-acting SNS agonist.It blocks uptake 1 protein. CNS effects- at low doses= euphoria, at high doses= CNS depression and respiratory failure. CVS- low does= tachycardia, vasoconstriction. Hogh doses= VF and cardiac arrest.
What is tyramine? What can it be described as? When is it a problem? Mechanism. (5)
A dietary amino acid found in red wine, cheese and soy sauce. Can be desrcibed as a indirectly-acting SNS agonist. Is a problem when the normal machnisms for degradation of monoamines aren’t in operation. Mechasims: 1) some weka agonist activity at post-synaptic adrenoceptors. 2) competes for take up by uptake 1. 3) displaces NA from intra-cellular storage esicles 4) COMPETES WITH NA FOR SITES ON MAO 5) cytosol NA leaks out into the synpase anyway.
4 general uses of SNS anatgonists
Hypertension, cardiac arrythmias, angina and glaucoma.
6 general unwanted effects of SNS antagonists
Bronchoconstriction, cardiac failure, hypoglycaemia, fatigue, cold extremities, bad dreams.
Propanolol- describe selectivity. Useful when? Describe method in arrhythmia.
B1 and B2. To prevent the effect of exercise/stress on HR, CO and arterial pressure. Works by decreasing sympathetic drive to the heart and increasing refractory period.
Atenolol- describe selectivity. Advantage. How do they work for angina? Contra-indications.
B1 selective (“cardioselective”). Less effect on airways than non-selective but this is concentration dependent. Work by reducing myocardial oxygen demand by decreasing HR, syst BP and contractile activity. Dont use if bradycardiac, hypotensive, with bronchospasms or severe CHF.
Labetolol- describe selectivity, Main use
a1 and B1 but 4:1 ratio. Mainly used to lower blood pressure (blocking a1 leads to vasodilation of visceral vascular)
Phentolamine- describe selectivity. Main use. Main problem. 1 other side effect.
Non-selective a agonist. Used to lower blood pressure but concomitant blockade of a1 enhances relfex tachycardia. Also increases GIT motility= diarrhoea.
