Ace inhibitors short note
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ACE Inhibitors - Short Note
Definition & Class
Angiotensin-Converting Enzyme (ACE) inhibitors are a class of antihypertensive and cardioprotective drugs that block the enzyme ACE, which converts angiotensin I (inactive) to angiotensin II (a potent vasoconstrictor). They end in the suffix "-pril".
Mechanism of Action
ACE inhibitors lower blood pressure via two complementary actions:
- Block ACE → prevents conversion of Ang I to Ang II → reduces vasoconstriction → arteriolar and venous dilation
- Prevent bradykinin breakdown (ACE also degrades bradykinin) → bradykinin accumulates → increases nitric oxide and prostacyclin production → further vasodilation
By lowering Ang II levels, ACE inhibitors also reduce aldosterone secretion → less sodium and water retention → decreased preload and afterload → reduced myocardial workload.
In the kidneys, efferent arteriolar vasodilation lowers intraglomerular pressure, providing renoprotection.
- Lippincott Illustrated Reviews: Pharmacology, p. 302
Examples (Common Drugs)
| Drug | Brand Name | Notes |
|---|---|---|
| Captopril | Generic | Short-acting; active drug (no prodrug conversion needed) |
| Enalapril | Vasotec | Prodrug; IV form (enalaprilat) available |
| Lisinopril | Prinivil, Zestril | Active drug; no hepatic conversion needed |
| Ramipril | Altace | Used post-MI |
| Fosinopril | Generic | Only one NOT eliminated by kidneys; no renal dose adjustment |
| Quinapril | Accupril | - |
| Benazepril | Lotensin | - |
| Perindopril | Generic | - |
| Trandolapril | Generic | - |
All except captopril and lisinopril are prodrugs requiring hepatic conversion to active metabolites. Fosinopril is unique in not requiring renal dose adjustment.
Therapeutic Uses
ACE inhibitors are first-line agents for:
- Hypertension (especially with compelling indications below)
- Heart failure with reduced ejection fraction (HFrEF) - reduce morbidity and mortality
- Post-myocardial infarction - improve ventricular remodeling and reduce LV hypertrophy
- Diabetic nephropathy - slow progression and reduce albuminuria
- Chronic kidney disease (CKD)
- Patients at high risk of coronary artery disease
- History of stroke
All ACE inhibitors are equally effective for hypertension at equivalent doses. - Lippincott, p. 303
Pharmacokinetics
- All are orally bioavailable (as drug or prodrug)
- Fosinopril: only member with dual excretion (renal + hepatic) - no renal dose adjustment needed
- Enalaprilat: only IV formulation in this class
- Captopril and lisinopril are active drugs (no hepatic conversion) - preferred in severe hepatic impairment
- Lippincott, p. 303
Adverse Effects
| Adverse Effect | Mechanism | Notes |
|---|---|---|
| Dry cough | Bradykinin/substance P accumulation in lungs | Up to 10% of patients; more common in women; resolves on stopping |
| Angioedema | Excess bradykinin causes submucosal swelling | Rare but potentially fatal; involves lips, mouth, throat; 5x more common in people of African ancestry |
| Hyperkalemia | Reduced aldosterone → less K+ excretion | Avoid potassium supplements and K+-sparing diuretics |
| First-dose hypotension | Especially in volume-depleted patients | - |
| Elevated creatinine | Reduced GFR from efferent dilation | Up to 30% rise above baseline is acceptable; do not stop |
| Skin rash / altered taste | - | Especially with captopril |
| Teratogenicity | Fetal renal impairment | Absolutely contraindicated in pregnancy |
Contraindications
- Pregnancy (teratogenic - fetal renal dysplasia, oligohydramnios)
- Bilateral renal artery stenosis (can precipitate acute renal failure)
- History of ACE inhibitor-induced angioedema
- Severe hyperkalemia
- Do NOT combine with ARBs (no added benefit, increased adverse effects) or aliskiren
ACE Inhibitors vs. ARBs (Key Comparison)
| Feature | ACE Inhibitors | ARBs |
|---|---|---|
| Bradykinin levels | Increased | Unchanged |
| Cough | Common (10%) | Rare |
| Angioedema | Rare | Very rare |
| Mechanism | Blocks ACE enzyme | Blocks AT1 receptor |
| Use in pregnancy | Contraindicated | Contraindicated |
ARBs are preferred when patients are intolerant of ACE inhibitor-induced cough. - Lippincott, p. 304; Goodman & Gilman
Mnemonic for Adverse Effects - "CAPTOPRIL"
- C - Cough
- A - Angioedema
- P - Potassium elevated (hyperkalemia)
- T - Taste altered
- O - (first-dose) hypOtension
- P - Pregnancy contraindicated
- R - Renal failure (in RAS)
- I - Increased creatinine
- L - Leukopenia (rare)
Short note according to shanbagh pharmacology book
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I have all I need. Here is the note written in Shanbhag's style - concise, exam-oriented, with numbered points, clear headings, and the typical Indian pharmacology exam format Shanbhag follows.
Note: Shanbhag's Pharmacology is not available in the library. The content below is written in Shanbhag's exact style and format (short, exam-focused, numbered subheadings, drug tables, uses/ADRs/CI structure) using standard pharmacology content from Katzung and Lippincott - which covers the same material Shanbhag presents.
ACE Inhibitors
(As per Shanbhag's Pharmacology style)
Introduction
ACE (Angiotensin-Converting Enzyme) inhibitors are drugs that block the enzyme ACE, thereby preventing conversion of angiotensin I to angiotensin II. They form an important class of antihypertensives, cardioprotective, and renoprotective agents.
Drugs
| Drug | Trade Name | Remarks |
|---|---|---|
| Captopril | Generic | Prototype; active drug; short-acting |
| Enalapril | Vasotec | Prodrug; oral + IV (enalaprilat) |
| Lisinopril | Prinivil, Zestril | Active drug (not a prodrug) |
| Ramipril | Altace | Post-MI cardioprotection |
| Fosinopril | Generic | Dual (renal + hepatic) excretion |
| Quinapril | Accupril | Long-acting |
| Perindopril | Coversyl | Long-acting |
| Trandolapril | Mavik | Long-acting |
| Benazepril | Lotensin | Long-acting |
All end in suffix "-pril". All except captopril and lisinopril are prodrugs that undergo hepatic hydrolysis to active forms.
Mechanism of Action
ACE (= kininase II) is a peptidyl dipeptidase enzyme that:
- Converts angiotensin I (inactive) → angiotensin II (potent vasoconstrictor)
- Inactivates bradykinin (vasodilator)
ACE inhibitors block both actions:
- ↓ Angiotensin II → ↓ vasoconstriction → ↓ peripheral vascular resistance
- ↑ Bradykinin → ↑ nitric oxide and prostacyclin → vasodilation (arterial + venous)
- ↓ Aldosterone secretion → ↓ Na⁺ and water retention → ↓ preload
- In kidney: efferent arteriolar dilation → ↓ intraglomerular pressure → renoprotection
- No reflex tachycardia (unlike direct vasodilators) - baroreceptor resetting + enhanced parasympathetic tone
Pharmacokinetics
| Feature | Detail |
|---|---|
| Route | Oral (all); IV - enalaprilat only |
| Prodrugs | All except captopril and lisinopril |
| Hepatic conversion | Required for prodrugs |
| Elimination | Renal (most); Fosinopril - renal + hepatic |
| Dose reduction in renal failure | Required for all except fosinopril |
| Preferred in hepatic failure | Captopril or lisinopril (no hepatic conversion needed) |
Therapeutic Uses
- Hypertension - first-line agent, especially with compelling indications:
- Diabetes mellitus
- Heart failure
- Post-MI
- CKD / Proteinuria
- High cardiovascular risk
- Congestive Heart Failure (CHF) - reduces preload + afterload; reduces mortality
- Post-Myocardial Infarction - prevents ventricular remodeling; reduces LV hypertrophy
- Diabetic nephropathy - reduces proteinuria, slows progression of CKD (even without hypertension)
- Chronic Kidney Disease - stabilizes renal function, reduces proteinuria
- Prevention of diabetes - in high cardiovascular-risk patients
Adverse Effects
(Mnemonic: CAPTOPRIL)
| Adverse Effect | Mechanism | Notes |
|---|---|---|
| Dry cough | ↑ Bradykinin + substance P in lungs | Up to 10% patients; more in women; resolves on stopping |
| Angioedema | ↑ Bradykinin → submucosal swelling | Rare but life-threatening; lips, tongue, throat; 5x more in Blacks |
| Hypotension (first dose) | Sudden ↓ BP | Especially in volume-depleted/HF patients |
| Hyperkalemia | ↓ Aldosterone → ↓ K⁺ excretion | Avoid K⁺ supplements + K⁺-sparing diuretics |
| Renal failure | In bilateral renal artery stenosis | ↓ GFR → acute renal failure |
| ↑ Serum creatinine | ↓ Intraglomerular pressure | Up to 30% rise acceptable; do NOT stop |
| Teratogenicity | Fetal renal hypoperfusion | Fetal anuria, oligohydramnios, malformations |
| Taste alteration / Rash | - | Especially captopril (sulfhydryl group) |
| Neutropenia / Proteinuria | - | Captopril - high doses in renal insufficiency |
Contraindications
- Pregnancy (all trimesters - teratogenic)
- Bilateral renal artery stenosis
- History of ACE inhibitor-induced angioedema
- Hyperkalemia
- Severe aortic stenosis (relative)
Drug Interactions
| Drug | Interaction |
|---|---|
| K⁺ supplements / K⁺-sparing diuretics | Severe hyperkalemia |
| NSAIDs | ↓ Antihypertensive effect (block bradykinin-mediated vasodilation) |
| ARBs / Aliskiren | Avoid combination - increased toxicity without added benefit |
| Lithium | ↑ Lithium levels (risk of toxicity) |
ACE Inhibitors vs ARBs (Shanbhag-style comparison)
| Feature | ACE Inhibitors | ARBs |
|---|---|---|
| Site of action | ACE enzyme | AT₁ receptor |
| Bradykinin | ↑ Elevated | Normal |
| Cough | Common (10%) | Rare |
| Angioedema | Rare | Very rare |
| Aldosterone | ↓ | ↓ |
| Use in pregnancy | Contraindicated | Contraindicated |
Key Points (Exam Tips)
- Prototype drug: Captopril (first ACE inhibitor introduced)
- Only IV ACE inhibitor: Enalaprilat
- No renal dose adjustment needed: Fosinopril (dual excretion)
- Cough due to: ↑ Bradykinin (switch to ARB if intolerant)
- Angioedema due to: ↑ Bradykinin (absolute contraindication for re-use)
- Most important use beyond hypertension: Diabetic nephropathy + Heart failure
- Do NOT use in: Pregnancy + Bilateral RAS
Content drawn from Katzung's Basic & Clinical Pharmacology 16e and Lippincott's Illustrated Reviews Pharmacology, structured in Shanbhag's exam format.
Nitric oxide short note cvs pharmacology
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Nitric Oxide (NO) - Short Note
(CVS Pharmacology - Shanbhag Style)
Introduction
Nitric oxide (NO) is a gaseous, free-radical signaling molecule (written as NO•) endogenously synthesized in the body. It is a key regulator of cardiovascular homeostasis - controlling vascular tone, blood pressure, platelet function, and cardiac remodeling. It must not be confused with:
- Nitrous oxide (N₂O) - anesthetic gas
- Nitrogen dioxide (NO₂) - toxic pulmonary irritant
Historical note: Nitroglycerin was used for angina in the 1860s; it was later discovered to work by releasing NO. NO was identified as the Endothelium-Derived Relaxing Factor (EDRF) - a discovery for which Furchgott, Ignarro, and Murad received the Nobel Prize (1998).
Synthesis of Nitric Oxide
NO is synthesized from L-arginine + O₂, catalyzed by Nitric Oxide Synthase (NOS) using NADPH as a cofactor. The byproduct is L-citrulline.
L-Arginine + O₂ + NADPH → NO + L-Citrulline
NOS Isoforms
| Isoform | Full Name | Location | Regulation |
|---|---|---|---|
| NOS-1 (nNOS) | Neuronal NOS | Neurons, skeletal muscle | Constitutive; Ca²⁺-dependent |
| NOS-2 (iNOS) | Inducible NOS | Macrophages, smooth muscle | Induced by inflammation/endotoxin; Ca²⁺-independent |
| NOS-3 (eNOS) | Endothelial NOS | Endothelium, platelets | Constitutive; Ca²⁺ + shear stress (PIEZO1 channel) |
eNOS is the key cardiovascular isoform. Triggered primarily by hemodynamic shear forces on endothelial cells - not just acetylcholine/Ca²⁺.
Mechanism of Action (Signaling Pathway)
Step-by-step:
- Shear stress / acetylcholine / bradykinin → ↑ Ca²⁺ in endothelial cells
- Ca²⁺-calmodulin complex → activates eNOS
- eNOS converts L-Arginine → NO
- NO diffuses freely across cell membranes into vascular smooth muscle
- NO binds to heme iron of soluble Guanylyl Cyclase (sGC) → activates sGC several hundredfold
- sGC converts GTP → cGMP
- cGMP activates Protein Kinase G (PKG)
- PKG → ↓ cytosolic Ca²⁺ → smooth muscle relaxation → vasodilation
In platelets: NO → ↑ cGMP → inhibits platelet aggregation (antithrombotic)
cGMP is broken down by Phosphodiesterase-5 (PDE-5). PDE-5 inhibitors (sildenafil) prolong cGMP action.
CVS Effects of Nitric Oxide
| Effect | Mechanism | Significance |
|---|---|---|
| Vasodilation (arteries + veins) | ↑ cGMP → ↓ smooth muscle Ca²⁺ | ↓ Peripheral vascular resistance, ↓ BP |
| Coronary artery dilation | eNOS-mediated | Prevents ischemia |
| ↓ Preload | Venodilation | Antianginal effect |
| Antiplatelet effect | ↑ cGMP in platelets | Prevents thrombosis |
| Anti-atherogenic | Inhibits vascular smooth muscle proliferation, leukocyte adhesion | Protects against atherosclerosis |
| Regulation of BP | eNOS knockout → hypertension | Tonic vasodilator tone |
| ↓ Cardiac remodeling | Reduces fibrosis | Cardioprotective |
NO Donors - Pharmacological Applications
These are prodrugs that release NO after biotransformation:
1. Organic Nitrates
- Nitroglycerin (GTN) - metabolized by mitochondrial aldehyde dehydrogenase-2 (enriched in veins) → predominantly venodilator → ↓ preload → antianginal
- Isosorbide dinitrate / mononitrate - longer acting
- Problem: Nitrate tolerance - continuous use → reactive oxygen species → inactivates aldehyde dehydrogenase-2 → loss of effect
2. Organic Nitrites
- Amyl nitrite (inhalant) - arterial vasodilator; no rapid tolerance
- Combining with PDE-5 inhibitors (sildenafil) = lethal hypotension (absolute contraindication)
3. Sodium Nitroprusside
- Dilates both arterioles and venules (balanced preload + afterload reduction)
- Used in hypertensive emergencies
- Biotransformation releases 5 cyanide molecules + 1 NO → risk of cyanide toxicity with prolonged use
4. Inhaled NO Gas
- Used in neonatal hypoxic respiratory failure and pulmonary arterial hypertension (PAH)
- Selectively dilates pulmonary vasculature → ↓ pulmonary artery resistance
- Stored as compressed gas with N₂ (inert diluent)
- Risks: NO + O₂ → NO₂ (pulmonary irritant); methemoglobin formation → monitor both
Drugs That Augment Endogenous NO Effects
PDE-5 Inhibitors
- Sildenafil, Tadalafil, Vardenafil
- Inhibit PDE-5 → ↑ cGMP persistence → prolonged vasodilation
- Used in: Erectile dysfunction, Pulmonary hypertension
sGC Stimulators
- Riociguat - binds sGC directly → ↑ affinity for NO → ↑ cGMP synthesis → pulmonary vasodilation
- Used in: Pulmonary arterial hypertension, Chronic thromboembolic PH
- Vericiguat - approved for heart failure with reduced EF → dilates pulmonary arteries → ↓ RV afterload
NO in Cardiovascular Disease
| Condition | Role of NO |
|---|---|
| Hypertension | ↓ eNOS activity / ↓ NO bioavailability → ↑ vascular tone |
| Atherosclerosis | ↓ NO → endothelial dysfunction → platelet adhesion + SMC proliferation |
| Diabetes | ↓ eNOS expression → ↓ NO → ↑ vascular tone + thrombosis risk |
| Heart failure | ↓ NO + oxidative stress → vasoconstriction + remodeling |
| Septic shock | iNOS massively upregulated → excess NO → profound hypotension |
| PAH | ↓ eNOS activity + reactive O₂ species scavenge NO → vasoconstriction + remodeling |
Inactivation of NO
- Half-life of NO: seconds (very short-lived)
- Rapidly reacts with:
- Hemoglobin (oxygenated Hb) → inactivation → ensures paracrine (local) not systemic action
- Superoxide (O₂⁻) → peroxynitrite (ONOO⁻) → toxic, causes tyrosine nitration → oxidative tissue damage
- Thiols → S-nitrosylation (some beneficial, some harmful)
- cGMP degraded by PDE-5 → terminates signaling
Summary / Exam Key Points
- NO = EDRF (endothelium-derived relaxing factor)
- Synthesized from L-Arginine by NOS; cofactors = NADPH, O₂, calmodulin
- Key isoform in CVS = eNOS (activated by shear stress)
- Mechanism: NO → sGC → cGMP → PKG → ↓ Ca²⁺ → vasodilation
- Nitroglycerin works via NO release → venodilation → ↓ preload → antianginal
- Nitroprusside = balanced arteriolar + venous dilation → hypertensive emergencies; cyanide risk
- Inhaled NO → used in neonatal respiratory failure + PAH
- PDE-5 inhibitors (sildenafil) + nitrates = fatal hypotension (contraindicated combination)
- In sepsis: iNOS overactivation → massive NO → refractory hypotension
- NOS inhibitors tried in sepsis - failed clinically (blocked beneficial eNOS too)
Sources: Katzung's Basic & Clinical Pharmacology 16e (Ch. 19), Braunwald's Heart Disease 12e - Lippincott Illustrated Reviews Pharmacology
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