Angiotensin-Converting Enzyme Inhibitors
Introduction
- First-line agents for pediatric heart failure and hypertension
- Common agents: Captopril, Enalapril, Lisinopril, Ramipril
- Proven safety profile in children with appropriate monitoring
- Available in various formulations including oral solutions
Mechanism of Action
ACE inhibitors work through multiple pathways:
- Inhibit conversion of angiotensin I to angiotensin II
- Decrease aldosterone secretion
- Increase bradykinin levels
- Reduce sympathetic nervous system activity
Physiologic Effects
- Vasodilation of both arterioles and venules
- Reduction in total peripheral resistance
- Decreased cardiac preload and afterload
- Improved cardiac output without reflex tachycardia
- Reduction in left ventricular remodeling
Clinical Indications
Primary Indications
- Systolic heart failure
- Hypertension (primary and secondary)
- Proteinuric kidney diseases
- Post-cardiac transplantation
- Marfan syndrome (to slow aortic root dilation)
- Single ventricle physiology
Specific Clinical Scenarios
- Left-to-right shunts with pulmonary overcirculation
- Dilated cardiomyopathy
- Preservation of renal function in chronic kidney disease
- Management of protein-losing enteropathy
Dosing Guidelines
Captopril
- Initial: 0.1-0.3 mg/kg/dose
- Frequency: Every 8-12 hours
- Maximum: 6 mg/kg/day
- Note: Start lower in neonates (0.05-0.1 mg/kg/dose)
Enalapril
- Initial: 0.08-0.1 mg/kg/dose
- Frequency: Every 12-24 hours
- Maximum: 0.5 mg/kg/day
- Note: Once-daily dosing possible in older children
Lisinopril
- Initial: 0.07-0.1 mg/kg/dose once daily
- Maximum: 0.5 mg/kg/day up to 40 mg/day
- Note: Convenient once-daily dosing
Monitoring & Safety
Required Monitoring
- Baseline: Blood pressure, serum creatinine, potassium, CBC
- Follow-up: Blood pressure at 1-2 weeks
- Labs: Creatinine and potassium at 1-2 weeks, then quarterly
- Growth parameters in chronic therapy
Major Adverse Effects
- Hypotension (especially first-dose)
- Hyperkalemia
- Acute kidney injury
- Angioedema (rare but serious)
- Chronic cough (10-20% of patients)
Contraindications
- Pregnancy (teratogenic)
- Bilateral renal artery stenosis
- History of angioedema
- Hyperkalemia
Key Practice Points
- Start at lower doses in volume-depleted patients
- Consider sodium restriction in resistant cases
- Monitor white blood cell count in autoimmune conditions
- Assess renal function before procedures requiring contrast
- Hold during acute illness with dehydration risk
