ACEi and cough

[Sir Gillies]

Hi guys,

I had a few questions that I hope someone can help me with...

1) does anyone know how ACEi cause cough? I imagine that it has to do with the increase of bradykinin, but not sure how...

2) Also on page 527 of FA, it says that ARBs have similar effects to ACEi but do not increase KALLIKREIN - do they mean bradykinin?

3) Also, can anyone point me to a good schematic diagram of the kinin system, or don't we need to know it?

Thanks in advance for your help.

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[Phloston]

Hi guys,

I had a few questions that I hope someone can help me with...

1) does anyone know how ACEi cause cough? I imagine that it has to do with the increase of bradykinin, but not sure how...

2) Also on page 527 of FA, it says that ARBs have similar effects to ACEi but do not increase KALLIKREIN - do they mean bradykinin?

3) Also, can anyone point me to a good schematic diagram of the kinin system, or don't we need to know it?

Thanks in advance for your help.

1) Bradykinin causes vasodilation. Stimulates cough reflex.

2) I've even seen in a practice question a while ago an answer choice that had to do with ACEi and kallikrein. If you look at the clotting cascade early in the haeme chapter, you'll notice kallikrein converts HMWH --> bradykinin. We always here ACE is "bradykininase," but it's also been suggested that ACE inhibits prokallikrein --> kallikrein, thereby decreasing bradykinin. ACE inhibitors increase kallikrein, causing increased bradykinin.

3) Look at FA.

 

[tiedyeddog]

1) Bradykinin causes vasodilation. Stimulates cough reflex.

2) I've even seen in a practice question a while ago an answer choice that had to do with ACEi and kallikrein. If you look at the clotting cascade early in the haeme chapter, you'll notice kallikrein converts HMWH --> bradykinin. We always here ACE is "bradykininase," but it's also been suggested that ACE inhibits prokallikrein --> kallikrein, thereby decreasing bradykinin. ACE inhibitors increase kallikrein, causing increased bradykinin.

3) Look at FA.

yeah, this is basically what pholston said but I like graphs and flowcharts so

Inhibiting ace =
1. no angiotensin I to angiotensin II
2. No inactivation of bradykinin

more bradykinin = more fluid retention in the lungs + dilation = higher hydrostatic pressure = leakage of fluid into the bronchioles = cough.

Hope this helps!