ANGIOTENSIN CONVERTING ENZYME/ACE inhibitors

1. AngiotensinConvertingEnzyme
Inhibitors
Dr zikrullah

2. Objectives
• Overview of ACEI
• Indications and Uses
• Effectiveness and
• The Evidence

3. Renin-Angiotensin-Aldosterone
System
• Juxtaglomerular apparatus secretes renin.
• Renin acts on angiotensinogen (gamma
globulin from the liver) giving angiotensin I
• Angiotensin converting enzyme (ACE) acts on
angiotensin I giving angiotensin II

4. • Renin:
1. It is secreted by the juxtaglomerular cells in
Kidney
2. Changes in secretion is in response to
changes in renal arterial pressure,
sympathetic nervous system signals and
some hormones
3. Its substrate is angiotensinogen

5. • Angiotensinogen
It is a glycoprotein synthesized and secreted into
the bloodstream by the liver
Angiotensinogen Renin angiotensin
ACE
Angiotensin III Angiotensin II

6. Renin-Angiotensin-Aldosterone System
• Angiotensin converting enzyme (ACE) is also
known as kinanase II
• It converts angiotensin I to II (vasoconstrictor) and
inactivates bradykinin (vasodilator)
• The principal site of its action is vascular
epithelium
• It is inhibited by synthetically produced Captopril
drug

7. Effects of Angiotensin IIEffects of Angiotensin II

8. • Aldosterone:
It is a mineralocorticoid produced in the adrenal
cortex
Increases cortical collecting tubule reabsorption
of Na+ and secretion of K+ and H+

9. Regulation of Aldosterone
• Angiotensin II and III stimulate aldosterone
release
• Changes in volume ( long Negative feedback
loop)
• Inhibition of renin secretion by angiotensin II
(short negative feedback loop)
• Endothelin and vasopressin stimulate
aldosterone secretion
• ANP is a potent inhibitor, dopamine also
inhibits it.

10. ACE Inhibitor Groups
A. Sulfhydryl-containing agents:
– Captopril , the first ACE inhibitor
B. Dicarboxylate-containing agents:
– Enalapril
– Ramipril
– Quinapril
– Perindopril
– Lisinopril
– Benazepril
C. Phosphonate-containing agents:
– Fosinopril
– Trandolapril

11. ACE inhibitors
• Captopril, lisinopril., enalapril, ramipril and
fosinopril etc.

12. Clinical Indications for ACEI
• Hypertension
• CHF
• Post MI
• Diabetes Mellitus
• Proteinuria
• Vascular Disease
• Post - transplant

13. ACE inhibitors in Hypertension
Captopril
• Sulfhydryl containing dipeptide and abolishes
pressor action of Angiotensin-I and not
Angiotensin-II and does not block AT receptors
• Pharmacokinetics:
– Available only orally, 70% - 75% is absorbed
– Partly absorbed and partly excreted unchanged in
urine
– Food interferes with its absorption
– Half life: 2 Hrs, but action stays for 6-12 Hrs

14. Captopril – Pharmacological
actions
1. In Normal:
– Depends on Na+ status – lowers BP marginally
on single dose
– When Na+ depletion – marked lowering of BP
2. In hypertensive:
– Lowers PVR and thereby mean, systolic and
diastolic BP
– RAS is overactive in 80% of hypertensive cases
and contributes to the maintenance of vascular
tone – inhibition causes lowering of BP

15. – Initially correlates with renin-angiotensin status
but chronic administration is independent of
renin activity
– Captopril decreases t.p.r on long term –
arterioles dilate – fall in systolic and diastolic BP
– No effect on Cardiac output
– Postural hypotension is not a problem - reflex
sympathetic stimulation does not occur
– Renal blood flow is maintained – greater
dilatation of vessels

16. DOSE OF Captopril--
Hypertension :
• Start: 12.5 to 25 mg 2-3 times/day; may
increase by 12.5 to 25 mg/dose at 1- to 2-
week intervals up to 50 mg 3 times/day

17. Dose of captopril
• CHF: Start 6.25 to 12.5 mg three times daily. Initial
dose depends upon patient's fluid/electrolyte
status. Target: 50 mg 3 times/day.
Prevention of LV dysfunction following MI: Oral:
Initial: 6.25 mg; followed by 12.5 mg 3 times/day;
increase to 25 mg 3 times/day over the next few
days; following by gradual increase to a goal of 50 mg
tid.

18. Dose of captopril
• Renal Dose Adjustments
• CrCl 10 to 50 mL/min: 75% of the normal dose
is recommended.
CrCl less than 10 mL/min: 50% of the normal
dose is recommended.

19. Captopril – Adverse effects
• Cough – persistent brassy cough in 20% cases
– inhibition of bradykinin and substanceP
breakdown in lungs
• Hyperkalemia in renal failure patients with K+
sparing diuretics, NSAID and beta blockers
(routine check of K+ level)
• Hypotension – sharp fall may occur – 1st dose
• Acute renal failure: CHF and bilateral renal
artery stenosis

20. • Angioedema: swelling of lips, mouth, nose etc.
• Dysgeusia: loss or alteration of taste
• Rashes, urticaria etc
• Foetopathic: hypoplasia of organs, growth
retardation etc
• Neutripenia
• Contraindications: Pregnancy, bilateral renal
artery stenosis, hypersensitivity and
hyperkalaemia

21. • 1st line of Drug:
–No postural hypotension or electrolyte
imbalance (no fatigue or weakness)
–Safe in asthmatics and diabetics
–Prevention of secondary
hyperaldosteronism and K+ loss
–Renal perfusion well maintained
Benefits of ACEI

22. – Reverse the ventricular hypertrophy and increase
in lumen size of vessel
– No No rebound hypertension
– hyperuraecemia or deleterious effect on plasma
lipid profile
– Minimal worsening of quality of life – general
wellbeing, sleep and work performance etc.

23. Additional Benefits of ACEI
• Prevention of diabetes
• Prevention of stroke recurrence
• Prevention of atrial fibrillation

24. How ACEI is useful in hypertension?
• ACE inhibitors block the conversion of
angiotensin I to angiotensin II
• Lower arteriolar and renovascular resistance
• Increase venous capacity,
• Increase cardiac output, cardiac index and
stroke volume.

25. Fixed Drug Combination
► To achieve recommended blood
pressure goals, it is often necessary to
combine two or more antihypertensive
agents.

26. Choice of antihypertensive agents
When implementing blockade of the renin–
angiotensin system start treatment with an ACE
inhibitor first then move to an ARB if the ACE
inhibitor is not tolerated.

27. Less effective
Diuretics Beta Blockers
ACEIs
ARBs
Calcium
Channel
Blockers
1-Receptor Blockers
Particularly effective
Adapted from Chalmers J. Clin Exp Hypertens. 1993;15:1299–1313.
Concomitant Use of
Antihypertensive Drugs

28. The Moral of the Tale
As long as we reach
the objective BP
below 140/90
(130/80), it doesn’t
matter how we get
there

29. ACEI and the Kidneys – Contd:
• Decreases Proteinuria (DM and Non-DM)
• Beneficial effect on permeability
• Beneficial effect on size selectivity
• Slow the Rate of GFR Decline

30. Pharmacotherapy –BP Control
• In people without CKD aim to keep the systolic
blood pressure below 140 mmHg (target range
120–139 mmHg) and the diastolic blood pressure
below 90 mmHg.
• In people with CKD and diabetes with urinary
protein excretion 1 g/24 h or more) aim to keep
the systolic blood pressure below 130 mmHg
(target range 120–129 mmHg) and the diastolic
blood pressure below 80 mmHg

31. ACEI and the Kidneys
Clinical studies have shown ACE inhibitors
reduce the progress of diabetic nephropathy
independently from their blood pressure-
lowering effect.
This action of ACE inhibitors is used in the
prevention of diabetic renal failure.

32. The Heart Matters – the effect of ACEI
• Prevents cardiac hypertrophy
• Limits infarct size
• Improves cardiac function
• Improves cardiac metabolism

33. ACEI in Heart Failure
• ACE inhibitors are recommended to treat HF
due to systolic dysfunction.
• The benefit of ACE inhibitors has been
demonstrated in all severities of symptomatic
HF and in patients with asymptomatic left
ventricular (LV) dysfunction.

34. ACE in Heart Failure: the evidence
A meta-analysis evaluated five trials
• Improvement in symptoms
• A lower total mortality.
• A lower rate of readmission for HF).

35. ACE Inhibitors for ‘Diastolic’ Heart
Failure?
• Guidelines for the management of heart
failure focus on patients with left ventricular
systolic dysfunction.
• However, guidelines make no
recommendation for their use in patients with
heart failure and preserved left ventricular
systolic function.

36. Type 2 diabetes
Management of cardiovascular risk factors
Lending our patients a hand

37. Can ACEI prevent Diabetes ?
• Several recent studies indicate that ACE
inhibitor therapy reduces the development of
type 2 diabetes in persons with essential
hypertension.
• HOPE, CAPPP, SOLVD, and ALLHAT
• DREAM & ONTARGET = more recent

38. Path physiology
• Exact mechanism is not known
• ACEI reduces oxidative stress
• Increases insulin sensitivity in the liver
• Reduces Insulin resistance in muscles
• Helps in the preservation of islet cells of
pancreas

39. Angiotensin Receptor Blockers e.g.
Losartan
• Block only the AT-1 subtype
• Comparable effects to ACE Inhibitors in almost
all situations.
• Less decrease in GFR in volume depleted
states
• Less side effects especially cough,
angioedema, rash
• Block all AII effects and not dependent on
particular pathway

40. • Theoretical superiority over ACEIs:
– Cough is rare – no interference with bradykinin
and other ACE substrates
– Complete inhibition of AT1 – alternative remains
with ACEs
– Result in indirect activation of AT2 – vasodilatation
(additional benefit)
– Clinical benefit of ARBs over ACEIs – not known

41. • However, losartan decreases BP in hypertensive
which is for long period (24 Hrs)
– heart rate remains unchanged and cvs reflxes are
not interfered
– no significant effect in plasma lipid profile, insulin
sensitivity and carbohydrate tolerance etc
– Mild uricosuric effect

42. ACE inhibitors versus ARBs: comparison of
practice guidelines and treatment selection
• ACC/AHA Heart Failure guidelines 2005. ACE
inhibitors should be prescribed to all patients
with left ventricular systolic dysfunction HF
(class IA recommendation).
• They recommend ARBs as a "reasonable
alternative" first-line therapy (class IIA
recommendation).

43. ACE inhibitors versus ARBs: comparison of
practice guidelines : Contd
• ACEI more cost effective
• ARB better tolerated than ACEI
• Deciding factor may be largely patient-
specific.

44. • The ACE inhibitor Enalapril has also been
shown to reduce cardiac cachexia in patients
with chronic heart failure
• Cachexia is a poor prognostic sign in patients
with chronic heart failure. ACE inhibitors are
now used to reverse frailty and muscle
wasting in elderly patients without heart
failure.

45. THANK YOU