What is Vasotec?
Vasotec (enalapril maleate) is an oral angiotensin-converting enzyme (ACE) inhibitor used to treat hypertension, symptomatic heart failure, and asymptomatic left ventricular dysfunction. 1
Mechanism and Formulation
Enalapril is a prodrug that requires bioactivation in the liver to its active form, enalaprilat, which inhibits the angiotensin-converting enzyme 1. This prevents conversion of angiotensin I to angiotensin II, thereby reducing peripheral vascular resistance and lowering blood pressure without increasing heart rate 2, 3.
The medication is available as 2.5 mg, 5 mg, 10 mg, and 20 mg tablets for oral administration 1.
FDA-Approved Indications
Vasotec has three primary indications 1:
- Hypertension: Effective alone or combined with other antihypertensives, particularly thiazide diuretics
- Symptomatic heart failure: Used in combination with diuretics and digitalis to improve symptoms, increase survival, and decrease hospitalization frequency
- Asymptomatic left ventricular dysfunction: In clinically stable patients with ejection fraction ≤35%, it decreases progression to overt heart failure and reduces hospitalization rates
Pharmacokinetics
The drug demonstrates a prolonged terminal half-life (>30 hours) due to enalaprilat binding to ACE, with an effective accumulation half-life of 11 hours following multiple dosing 4. Peak serum concentrations occur 4 hours post-dose, with steady-state achieved by the fourth daily dose 4. Excretion is 100% renal 1, 4.
Hemodynamic Effects
Enalapril lowers blood pressure by decreasing systemic vascular resistance while slightly increasing cardiac output and stroke volume, without causing reflex tachycardia 2, 3. It increases renal blood flow and decreases renal vascular resistance 4.
Important Renal Considerations
Monitor renal function carefully, particularly in high-risk patients 5:
- A 10-20% rise in serum creatinine after initiation is common in heart failure patients and typically stabilizes
- Greater creatinine increases occur more frequently with underlying chronic renal insufficiency
- Acute renal failure risk factors include: systemic hypotension (MAP <65 mmHg), volume depletion, bilateral renal artery stenosis, or concomitant nephrotoxins
- Temporarily discontinue if acute renal failure develops while correcting precipitating factors 5
Key Safety Warnings
Hyperkalemia: Relatively common but usually modest (≈1 mEq/L increase). Monitor potassium early after initiation, especially in patients with diabetes or chronic renal failure 5.
Surgical considerations: May cause profound hypotension during anesthesia, particularly cardiac surgery. Some suggest withholding 24-48 hours before surgery, though evidence is conflicting 5.
Population-specific concerns 1:
- Black patients may have reduced blood pressure response compared to non-blacks
- Black patients have higher incidence of angioedema with ACE inhibitors
- Risk of agranulocytosis exists, particularly in patients with renal impairment or collagen vascular disease
Common Adverse Effects
The most frequent adverse effect limiting ACE inhibitor therapy in clinical practice is dry cough 3. In comparative studies, enalapril carries a significantly higher risk of dry cough than angiotensin receptor blockers (risk ratio 2.88) 6. Other adverse effects are generally uncommon and mild 7.