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16 Cards in this Set
- Front
- Back
These antagonists bind α- or β-adrenoceptors at target organs, inhibiting α- or β-adrenoceptor mediated effects, respectively. They block endogenous and exogenous ____ agonists (e.g. E, NE, phenylephrine, isoproterenol and salbutamol) |
Adrenoceptor antagonists |
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This α-adrenoceptor antagonist blocks both α1 and α2 -adrenoceptors |
Phentolamine |
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This α-adrenoceptor antagonist selectively blocks α1- adrenoceptors. -> Reduce blood pressure of hypertensive patients. Toxicities include nasal stuffiness, orthostatic hypotension and reflex tachycardia |
Prazosin -nasal stuffiness - due to blood flow to the mucus membrane -orthostatic hypotension - dilatation of veins thereby reducing return of blood to the heart -tachycardia due to reflex increase in sympathetic discharge in response to a decrease in blood pressure (and subsequent β-adrenoceptor activation). |
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This β-adrenoceptor antagonist blocks β1- and β2– adrenoceptors
Mechanism of action involves blocking β1-adrenoceptors: -in the central NS -> reduce sympathetic outflow -in the peripheral NS (at pre-junctional sympathetic nerve terminal -> reduce NE release
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Propranolol
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This β-adrenoceptor antagonist selectively blocks β1-adrenoceptors antagonist Mechanism of action involves blockade of β1-adrenoceptors in the CNS to reduce sympathetic outflow and peripherally (at pre-junctional sympathetic nerve terminal) to reduce NE release. |
Metoprolol |
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Both Propranolol and Metoprolol are so-called cardiac protective, blocking B1 adrenoceptors -> decrease SNA, CO, HR/cardiac work... Drug use? |
Prevent increased HR and CO during exercise. Treat hypertension and angina/myocardial infarction. |
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Propranolol blocks β1-adrenoceptor -> dec SNA blocks β2– adrenoceptors -> reduce tremor inskeletal muscles Drug use? |
management of acute panic symptoms and performance anxiety. |
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Toxicities of β-adrenoceptors antagonists
β1-adrenoceptors blockers reduces heart rate and cardiac contraction -> toxicity?
β2-adrenoceptors blockers -> bronchoconstriction -> toxicity? |
Reduced cardiac function, congestive heart failure (may worsen heart failure in patients with high β1-adrenergic tone).
Asthma attack in patients with asthma |
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These drugs inhibit transmitter (NE and E) release from adrenergic nerves, blocking adrenergic neurons -> reduce the activity of the SNS, but not the actions of already circulating E, NE or sympathomimetic drugs. |
Antiadrenergic drugs |
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Both of these antiadrenergics activate central and peripheral prejunctional α2-adrenoceptors -> reduce sympathetic outflow and release of E and NE. |
Clonidine and α-methyl dopa |
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This antiadrenergic drug blocks VMAT -> reduces uptake of DA and NE into storage vesicles -> prevents NT release. |
Reserpine |
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This antiadrenergic drug is taken up via Uptake-1 into the sympathetic nerve terminal. Large [drug] in the nerve terminal -> blocks Na+ influx -> inhibits AP propagation -> blocks release of NE from storage vesicles.
->-> depletes NE stores at the nerve terminal. |
Guanethidine |
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These drugs bind to and inhibit the action of nicotinic receptors at both sympathetic and parasympathetic ganglia; their influences depend on predominance of parasympathetic or sympathetic tone at a particular site. |
Ganglionic blockers (e.g., hexamethonium) |
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Ganglionic blocker -> Inhibit activity in organs with high parasympathetic tone: heart eye gastrointestinal organs genitourinary organs -> effect of inhibition? (Think, what does PNS stimulation do? What is opposite?) |
Increase heart rate Mydriasis Paralysis of accommodation Decreased gastrointestinal tone and motility Urinary retention |
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Ganglionic blocker -> Inhibit activity in organs with predominate sympathetic tone: BV-- arterioles veins -> effect of inhibition? (Think, what does SNS stimulation do? What is opposite?) |
Vasodilation (arterioles) Venodilation (vein) -> reduced BP -> pooling of blood in the lower limbs |
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To review, Ganglionic blockers (e.g. hexamethonium) -> ? |
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