ACE-inhibitors

Question 1

What are some examples of ACE-i’s and what do they do

Answer 1

• Ramipril, enalapril, captopril, perindopril

- Reduce blood pressure

Question 2

What are the indications for use

Answer 2

• HTN (1st line)
• HF
• CVD prevention/management - post-MI, mild CKD, diabetic nephropathy

Question 3

What do ACE-i’s do

Answer 3

• control BP, blood volume, electrolyte haemostasis

Question 4

What is the mechanism of renin-angiotension-aldosterone system (RAAS)

Answer 4

Angiotensinogen —(RENIN)—> Angiotensin 1 —-(ACE)—> Angiotensin 2

• Renin released from juxtaglomerular apparatus in response to falling Na2+ levels, decreased renal perfusion, sympathetic activity
• Ang1 formed in liver + then circulates in blood
• ACE found in pulmonary circulation + in endothelium of BVs
• Ang2 vasoconstricts, increases aldosterone, ADH + sympathetics

Question 5

What is the mechanism of action of ACE-i

Answer 5

• Prevent conversion of Ang1 to Ang2
• Blocking Ang2 reduced peripheral vascular resistance (afterload) –> lowers BP
• Dilates efferent glomerular arteriole (reduce intraglomerular pressure + slow prg CKD)
• Reducing aldosterone = ++ Na and H2O excretion - help reduce venous return (preload) - beneficial in HF

Question 6

What are the side effects of ACEi

Answer 6

• Hypotension (particularly after 1st dose)
• Persistent dry cough (++ levels bradykinin –> usually inactivated by ACE)
• Hyperkalaemia (lower aldersterone promotes K+ retention)
• Cause/ worsen renal failure
• Angioedema/ anaphylactoid reactions

Question 7

What are the contra-indications

Answer 7

• Renal artery stenosis
• Acute kidney injury
• Pregnancy/ breastfeeding

Question 8

What are the interactions

Answer 8

• Potassium elevating drugs (risk of hyperkalaemia already) e.g. potassium-sparing diuretics
• NSAID - increases risk renal failure