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# ACE Inhibitors
## Overview
Angiotensin-converting enzyme (ACE) inhibitors are a class of medications primarily used to manage hypertension and heart failure. They work by blocking the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, leading to vasodilation and reduced blood pressure.
## Primary Indications
* Hypertension
* Congestive Heart Failure (CHF)
* Post-Myocardial Infarction (MI) (to improve survival)
* Diabetic Nephropathy (to slow progression)
* Proteinuric Chronic Kidney Disease
## Adult Dosing
Dosing is highly individualized and depends on the specific agent, indication, and patient response. Doses are typically started low and titrated upwards.
* **Hypertension:** Initial doses vary by agent (e.g., lisinopril 10 mg once daily, enalapril 5 mg once or twice daily, ramipril 2.5 mg once daily). Usual maintenance doses range from 10-40 mg daily for lisinopril, 10-40 mg daily for enalapril, and 5-10 mg daily for ramipril. Maximum doses are generally agent-specific.
* **Heart Failure:** Initial doses are often lower than for hypertension to avoid hypotension (e.g., lisinopril 5 mg once daily, enalapril 2.5 mg once or twice daily, ramipril 1.25 mg once daily). Doses are titrated up as tolerated, often to target doses of lisinopril 20 mg once daily, enalapril 20 mg twice daily, or ramipril 5 mg twice daily, or the maximum tolerated dose.
* **Post-MI:** Generally initiated within 24 hours in stable patients with evidence of LV dysfunction or heart failure, often starting at low doses (e.g., captopril 6.25 mg TID, enalapril 2.5 mg BID) and titrated up as tolerated.
* **Diabetic Nephropathy/Proteinuric CKD:** Typically initiated at standard doses for hypertension and titrated as tolerated, aiming for blood pressure control and reduction in proteinuria.
## Pediatric Dosing
Established pediatric dosing varies by agent and indication.
* **Hypertension:**
* **Enalapril:** 0.07-0.1 mg/kg/dose once daily (max 40 mg/day).
* **Lisinopril:** 0.07-0.2 mg/kg/dose once daily (max 40 mg/day).
* **Ramipril:** 0.05 mg/kg/dose once daily (max 10 mg/day).
* **Congestive Heart Failure:** Generally similar to hypertension dosing but may require closer monitoring.
## Dose Adjustments
* **Renal Impairment:** Reduce initial dose and titrate slowly based on renal function (serum creatinine, GFR) and potassium levels. Specific dose reductions depend on the agent and degree of renal impairment.
* **Hepatic Impairment:** Generally no specific dose adjustment, but caution and slow titration are advised.
## Contraindications
* History of angioedema related to previous ACE inhibitor treatment.
* Hereditary or idiopathic angioedema.
* Concomitant use with aliskiren in patients with diabetes mellitus or renal impairment.
* Pregnancy (especially second and third trimesters).
* Hypersensitivity to the specific ACE inhibitor.
## Adverse Effects
* **Common:** Cough (dry, persistent), dizziness, headache, fatigue, hypotension, hyperkalemia.
* **Less Common/Serious:** Angioedema (can be life-threatening), acute kidney injury, rash, taste disturbances, neutropenia/agranulocytosis (rare).
## Key Drug Interactions
* **Potassium-Sparing Diuretics (e.g., spironolactone, amiloride), Potassium Supplements, Salt Substitutes:** Increased risk of hyperkalemia.
* **NSAIDs, COX-2 Inhibitors:** May reduce antihypertensive effect and increase risk of renal impairment, especially in the elderly or volume-depleted patients.
* **Diuretics (especially thiazides, loop diuretics):** Increased risk of hypotension, particularly with initial doses.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **mTOR Inhibitors (e.g., sirolimus, everolimus):** Increased risk of angioedema.
* **ARBs (Angiotensin II Receptor Blockers):** Increased risk of hyperkalemia, hypotension, and renal dysfunction. Concomitant use is generally not recommended outside of specific heart failure protocols with close monitoring.
* **Aliskiren:** Increased risk of adverse events including hyperkalemia and hypotension; contraindicated in patients with diabetes or renal impairment.
## Monitoring
* **Baseline:** Serum creatinine, electrolytes (especially potassium), blood pressure.
* **During Therapy:**
* **Renal Function:** Monitor serum creatinine and GFR within 1-2 weeks of initiation or dose increase, and periodically thereafter (frequency depends on indication, renal function, and other comorbidities).
* **Potassium:** Monitor electrolytes within 1-2 weeks of initiation or dose increase, and periodically thereafter, especially in patients with renal impairment or on other agents that affect potassium.
* **Blood Pressure:** Monitor regularly to assess efficacy and detect hypotension.
* **Signs/Symptoms of Angioedema:** Patient education is crucial.
## Clinical Pearls
* The characteristic dry cough is thought to be due to bradykinin accumulation and is generally reversible upon discontinuation.
* Initiate at low doses and titrate slowly, especially in patients who are volume-depleted, salt-depleted, elderly, or have significant renal impairment, to minimize the risk of symptomatic hypotension.
* First-dose hypotension can occur, particularly in patients taking diuretics. Consider discontinuing the diuretic 2-3 days prior to initiating an ACE inhibitor or starting the ACE inhibitor at a lower dose.
* Angioedema can occur at any time during therapy and is a medical emergency. Educate patients to seek immediate medical attention if symptoms develop.
* ACE inhibitors are generally considered renoprotective in patients with diabetes and proteinuria, but close monitoring of renal function and potassium is essential.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details and to verify accuracy before making clinical decisions.*
