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Old 09-21-2011
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Default Atenolol VS Captopril

A person has hypertension. He is given a drug that decreases sodium absorption and decreases potassium excretion from distal tubule.

Which drug is most likely the one and how can you explain? Atenolol or captopril?
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Old 09-21-2011
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Its Captopril-ACE inhibitor as it decrease the synthesis of aldosterone resulting in decrease activity of aldosterone receptor which result in decrease absorption of Na and water.Because of decrease in absorbtion of Na will result in no positive charge intacellularly hence K are not excreted out which were initially exctreted to keep intracellular electrical neutral.
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Old 09-21-2011
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Thanks. You are correct, just like what Kaplan said.

But I was actually thinking beta-blockers could do the same. As renin release is caused Beta-1 stimulation, Atenolol (selective Beta-1 receptor blocker) will decrease renin release. With the decreased renin release, there would be less angiotensin II and hence less aldosterone release. Less aldosterone means less Na+ absorption and less K+ excretion at collecting duct.

So the real question is aren't both of these drugs leading to the same effect? Or is there something incorrect about my understanding. Or is it just because ACEI works closer to the end of the R-A-A pathway, making it a better answer?
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Old 09-21-2011
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I think the main action of beta blocker is its action on heart by decreasing CO(cardiac output).Continous decrease in CO overtime can itself act as stimulus to inrease renin production which can counteract the direct action of beta blocker on RAAS.
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