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Old 11-19-2011
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Sphygmomanometer Why beta blockers and hypertension?

Hi,

Just can't understand mechanism of action of beta blocker in hypertension since it blocks b2 receptors and cause vasoconstriction?
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Old 11-19-2011
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Beta blockers are not the first line therapy for hypertension. They are specifically used in situations such as post-MI or congestive heart failure. Otherwise for regular essential hypertension we don't use them.

The drugs that are used are generally those who have B1 selective effects with minimal B2 effects such as Atenolol.

When you block B1, you decrease the heart rate and myocardial contractility, such effects are desirable in the case of hypertension.

Also, remember that B2 are not innervated, which means if you block it, there won't be a problem, only if there is an opposing parasympathetic (circulating acetyl choline) overactivity such as patients with asthma or vasospastic conditions such as Prinzmetal angina or Raynaud's.

So in general we think of the B1 effects (receptors mainly present in the heart and not in the vasculature) when we talk about beta blockers in hypertension.

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Old 11-19-2011
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I think Betablocker also prevent RAAS activation like in CHF, where RAAS is counterproductive after a certain time.
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Old 11-20-2011
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thank you so much
but also in another subject about ACEi as it states in uworld that they cause constriction in afferent of glomerular capillaries
how is that while they block angitensin II action????
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Old 11-20-2011
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Hey flowerlady are you sure? I always read the opposite Which question in uworld are you refering to?
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Old 11-13-2012
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Beta blockers cause a decrease in renin secretion that's why they are antihypertenssive, but the exact mechanism is not fully understood
i checked many sources and my info are 100% legit
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Old 11-13-2012
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Quote:
Originally Posted by flowerlady View Post
thank you so much
but also in another subject about ACEi as it states in uworld that they cause constriction in afferent of glomerular capillaries
how is that while they block angitensin II action????
Probably they cause it because they ultimatley inhibit angiotensin action on efferent arteriole this causes an increased bloodflow through the glomerular capillaries causing increased hydrostatic pressure Near the distal tubule which causes increased Na and H2O content in the distal tubule stimulating the macula densa which ultimately constricts rhe afferent arteriole to reduce the load to the tubules
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