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# ACE Inhibitors
## Overview
Angiotensin-Converting Enzyme (ACE) inhibitors block the conversion of angiotensin I to angiotensin II, leading to systemic vasodilation, reduction in aldosterone secretion, and inhibition of cardiac/vascular remodeling.
## Primary Indications
Hypertension, heart failure (HFrEF), post-myocardial infarction, and chronic kidney disease (diabetic nephropathy/proteinuria).
## Adult Dosing
*(Representative examples based on common agents)*
* **Lisinopril:** Hypertension: 10 mg once daily (max 40 mg); Heart failure: 2.5–5 mg once daily (max 40 mg).
* **Enalapril:** Hypertension: 5 mg once/twice daily (max 40 mg); Heart failure: 2.5 mg twice daily (max 20–40 mg).
* **Ramipril:** Hypertension: 2.5 mg once daily (max 20 mg); Post-MI/CV risk reduction: 2.5 mg twice daily titrated to 5 mg twice daily.
## Pediatric Dosing
Dosing is highly dependent on weight and age; institutional protocols or specialized references (e.g., Harriet Lane Handbook) are mandatory.
* **Enalapril:** Usual starting dose 0.08 mg/kg once daily, titrated as needed.
* **Lisinopril:** Usually initiated at 0.07 mg/kg once daily.
* *Note:* Safety and efficacy in neonates are not established.
## Dose Adjustments
* **Renal Impairment:** Reduce starting doses and titrate slowly for CrCl <30 mL/min.
* **Hepatic Impairment:** Generally not required, though clinical response may be altered.
* **Elderly/Volume Depleted:** Initiate at the lowest authorized dose to avoid profound hypotension.
## Contraindications
* History of angioedema (hereditary or ACE-inhibitor induced).
* Concurrent use with aliskiren in diabetic patients.
* Concomitant use with neprilysin inhibitors (e.g., sacubitril) — requires a 36-hour washout period.
* Pregnancy (Category D: causes fetal injury/death).
## Adverse Effects
* **Common:** Dry, persistent cough (bradykinin-mediated), headache, dizziness.
* **Serious:** Angioedema (life-threatening airway obstruction), hyperkalemia, acute kidney injury, neutropenia (rare).
## Key Drug Interactions
* **Potassium-sparing diuretics/supplements:** Increases risk of severe hyperkalemia.
* **NSAIDs:** May reduce antihypertensive efficacy and increase risk of acute renal failure.
* **Lithium:** May lead to lithium toxicity by reducing renal excretion.
* **ARBs/Renin Inhibitors:** Dual blockade increases risk of hyperkalemia, hypotension, and renal dysfunction.
## Monitoring
* **Baseline/Follow-up:** Serum creatinine and potassium (within 1–2 weeks of initiation or dose change).
* **Blood Pressure:** Regular monitoring for orthostasis and therapeutic effect.
* **Angioedema:** Patient education on early symptoms (tongue/lip swelling, difficulty breathing).
## Clinical Pearls
* The dry cough is not dose-dependent; if it develops and impairs quality of life, transition to an Angiotensin Receptor Blocker (ARB).
* ACE inhibitors are generally not the first-line antihypertensive choice in Black patients due to lower efficacy and higher risk of angioedema.
* Monitor for "first-dose hypotension," especially in patients on diuretics or those who are salt/volume depleted.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult current institutional protocols, standardized clinical references (e.g., Lexicomp, Micromedex), and the FDA-approved package insert before prescribing or administering medication.
