SNS Antagonists Flashcards
Describe the effects of each type of adrenoceptor. Alpha 1 Alpha 2 Beta 1 Beta 2 Beta 3
Alpha 1: Vasoconstriction + GIT relaxation
Alpha 2: Inhibition of transmitter release + Contraction of vascular smooth muscle + CNS actions
Beta 1: increased HR + contractility, increased renin release + GIT relaxation
Beta 2: Bronchodilation, Vasodilation, Relaxation of visceral smooth muscle + Hepatic glycogenolysis
Beta 3: Lipolysis
State 5 adrenoceptor antagonists including the receptors that they block.
Carvedilol = alpha 1 + beta 1 Phentolamine = alpha 1 + alpha 2 Prazosin = alpha 1 Propranolol = beta 1 + beta 2 Atenolol = beta 1
State 4 main clinical uses of SNS antagonists and false transmitters.
Hypertension
Angina
Arrhythmia
Glaucoma
What is defined as hypertension?
Sustained BP > 140/90 mm Hg
State 3 elements that contribute to hypertension.
Blood volume
Peripheral vascular tone
Cardiac output
What are the target tissues for hypertensives? What effect do beta blockers have on these?
Heart: reduces FOC + HR
Kidney: blocks renin release, blocks production of AII (vasoconstrictor) + aldosterone
CNS: Reduces sympathetic tone
Blockade of facilitatory effects of presynaptic B-adrenoceptors on NA release
Blockade of which receptors cause the positive and negative effects of beta-blockers?
Beta 1 blockade = positive effects
Beta 2 blockade = negative effects
What are beta-1 selective blockers called?
Cardioselective Beta-blockers
How does the effect of beta-blockers on the heart change?
The effect of beta blockade on the heart disappears with chronic treatment as the heart begins to reset itself
What is the effect of presynaptic beta 1 receptors?
positive facilitation effect on the synthesis + release of noradrenaline
State 4 conditions in which you would not give a patient a betablocker. Explain each of them.
Asthma: blockade of B2 receptors in the lungs can prevent B2 mediated bronchodilation, can be fatal
Cardiac Failure: these patients rely on a certain degree of sympathetic drive to the heart to maintain adequate CO
COPD: same reason as asthma
Diabetes: B blockade masks the symptoms of hypoglycaemia (tremors, palpitations, sweating) + B2 blockade inhibits hepatic glycogenolysis
State 3 unwanted actions of beta-blockers.
Fatigue
Cold extremities
Bad dreams
What effect does propranolol have on heart rate, cardiac output and blood pressure?
Little effect on these parameters at rest
Decreases all of these parameters when exercising
Why would you still not give a cardioselective beta-blocker to anasthmatic patient?
Selectivity is dependent on concentration
List 4 types of beta blocker
Non selective: Propanolol
B1-selective: Atenolol (more selective for B1)
Mixed B-A blockers: Carvedilol (A1 blockade gives additional vasodilator properties)
New: Nebivolol (potentiates NO) + Sotalol (Inhibits K+ channels)
What is the main mediator of total peripheral resistance?
Alpha 1 mediated vasoconstriction
What are the effects of alpha blockade?
Vasodilation causing a fall in TPR + hence a fall in BP
What reflex will be triggered by alpha blockade?
Baroreceptor mediated reflex tachycardia to increase HR + CO