Angiotensin-Converting Enzyme (ACE) Inhibitors are a cornerstone in the management of hypertension, heart failure, and myocardial infarction. These drugs play a crucial role in controlling the Renin-Angiotensin-Aldosterone System (RAAS), helping to relax blood vessels and improve blood flow throughout the body.
ACE inhibitors are easily identified by their common suffix “-pril”, which includes drugs such as Captopril, Enalapril, and Lisinopril.
Let’s explore the mechanism, uses, adverse effects, contraindications, and key mnemonics in a student-friendly format.
Classification
| Category | Type |
|---|---|
| Pharmacologic (P) | ACE Inhibitors |
| Therapeutic (T) | Antihypertensives |
Common ACE Inhibitors:
- Captopril
- Enalapril
- Lisinopril
- Ramipril
- Perindopril
- Benazepril
All end with the suffix “-pril”, which makes them easy to remember.
Mechanism of Action (MOA)
ACE inhibitors act by blocking the conversion of Angiotensin I to Angiotensin II.
Step-by-step mechanism:
1. Normally, the Angiotensin-Converting Enzyme (ACE) converts Angiotensin I → Angiotensin II, a potent vasoconstrictor.2. By inhibiting ACE, these drugs prevent the formation of Angiotensin II.
3. As a result:
- Blood vessels relax (vasodilation)
- Aldosterone secretion decreases → Less sodium and water retention
- Blood volume and pressure drop
Additionally, ACE inhibitors prevent the breakdown of bradykinin, a compound that promotes vasodilation — this enhances the blood-pressure-lowering effect but can also cause the well-known “ACE cough.”
Clinical Uses
ACE inhibitors are prescribed for a range of cardiovascular and renal conditions:
1. Hypertension (High Blood Pressure) – First-line agents, especially in young or diabetic patients.Adverse Effects – Remember with the Mnemonic “APRIL”
Since all ACE inhibitors end in “PRIL”, the mnemonic APRIL helps recall their key side effects:
| Letter | Adverse Effect | Explanation |
|---|---|---|
| A | Angioedema | Swelling of lips, face, or tongue due to increased bradykinin. |
| P | Potassium Elevated | Reduced aldosterone → potassium retention → hyperkalemia. |
| R | Recurrent Cough | Due to bradykinin buildup in the lungs. |
| I | Itchy Skin | Mild allergic or vasodilatory reaction. |
| L | Low Blood Pressure | From decreased vascular resistance and fluid loss. |
Mnemonic tip:
“APRIL” = Side effects of “-pril” drugs.
Drug Interactions
| Drug | Interaction Effect |
|---|---|
| Diuretics | Increase risk of hypotension (especially first dose). |
| Lithium | Increases lithium toxicity due to reduced clearance. |
| NSAIDs | May reduce the antihypertensive effect by interfering with kidney function. |
Monitoring is essential when combining ACE inhibitors with these agents.
Contraindications
ACE inhibitors should not be used in the following conditions:
1. Pregnancy – Can cause fetal injury, especially in the second and third trimesters.Black Box Warning
“Increased risk of fetal injury or death when administered during pregnancy.”
Hence, ACE inhibitors are contraindicated in pregnant women and those planning pregnancy.
Advantages of ACE Inhibitors
- Effective in reducing mortality in heart failure and post-MI.
- Provide renal protection in diabetic patients.
- Do not cause reflex tachycardia, unlike some other antihypertensives.
- Improve cardiac remodeling by reducing afterload and preload.
ACE Inhibitors vs. ARBs (Angiotensin II Receptor Blockers)
| Feature | ACE Inhibitors (“-pril”) | ARBs (“-sartan”) |
|---|---|---|
| Mechanism | Block conversion of Angiotensin I → II | Block Angiotensin II receptor |
| Bradykinin Effect | Increased (causes cough, angioedema) | None (no cough) |
| Common Side Effect | Dry cough | Rare angioedema |
| Preferred When | First-line for hypertension | Patient is intolerant to ACE inhibitor cough |
| Suffix | “-pril” | “-sartan” |
Both classes lower blood pressure but differ in side effect profiles.
Clinical Monitoring
While on ACE inhibitors, patients should undergo regular checks for:
- Serum potassium → to detect hyperkalemia
- Serum creatinine → to monitor kidney function
- Blood pressure → to adjust dosing if needed
Summary Table
| Parameter | Details |
|---|---|
| Drug Class | Angiotensin-Converting Enzyme (ACE) Inhibitors |
| Common Drugs | Captopril, Enalapril, Lisinopril |
| Mechanism | Blocks conversion of Angiotensin I → II; reduces RAAS activity |
| Uses | Hypertension, Heart Failure, Myocardial Infarction, Diabetic Nephropathy |
| Mnemonic for Adverse Effects | APRIL = Angioedema, Potassium ↑, Recurrent cough, Itchy skin, Low BP |
| Interactions | Diuretics (hypotension), Lithium (toxicity) |
| Contraindications | Pregnancy, Renal impairment, Hypotension |
| Black Box Warning | Fetal injury during pregnancy |
FAQs About ACE Inhibitors
Q1. Why are ACE inhibitors preferred for diabetic patients?
They reduce intraglomerular pressure and proteinuria, offering kidney protection in diabetes.
Q2. Why do ACE inhibitors cause cough?
Because they increase bradykinin levels, which can irritate the respiratory tract.
Q3. Which suffix helps identify ACE inhibitors?
All ACE inhibitors end with “-pril”, such as Captopril and Lisinopril.
Q4. What should patients avoid while taking ACE inhibitors?
Avoid potassium supplements or potassium-sparing diuretics, as these may cause hyperkalemia.
Q5. What’s the difference between ACE inhibitors and ARBs?
ACE inhibitors block enzyme conversion; ARBs block receptor binding. ARBs do not cause a cough.
