Drug Monograph
Enalapril (Vasotec)
enalapril maleate
Pharmacokinetic Profile
Half-Life
11 h (effective accumulation)
Metabolism
Hepatic CES1 (prodrug → enalaprilat)
Protein Binding
50–60%
Bioavailability
~60% (oral)
Tmax
1 h (enalapril); 3–4 h (enalaprilat)
Clinical Information
Drug Class
ACE Inhibitor
Available Doses
2.5, 5, 10, 20 mg tablets; 1 mg/mL oral solution
Route
Oral; IV (enalaprilat 1.25 mg/mL)
Renal Adjustment
Yes — CrCl ≤30 mL/min
Hepatic Adjustment
Not required
Pregnancy
Contraindicated (Boxed Warning)
Lactation
Not recommended
Schedule
Prescription only (not scheduled)
Generic Available
Yes (since 2000)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Hypertension | Adults and children ≥1 month | Monotherapy or combination | FDA Approved |
| Symptomatic heart failure | Adults | Usually combined with diuretics ± digitalis | FDA Approved |
| Asymptomatic left ventricular dysfunction (EF ≤35%) | Adults | Monotherapy or combination | FDA Approved |
Enalapril is a cornerstone ACE inhibitor with robust evidence across the cardiovascular disease spectrum. The AHA/ACC/HFSA 2022 guideline positions ACE inhibitors as part of guideline-directed medical therapy for heart failure with reduced ejection fraction (HFrEF). The SOLVD Prevention and Treatment trials demonstrated that enalapril reduces hospitalisations and slows progression from asymptomatic to symptomatic heart failure.
Off-Label Uses
Diabetic nephropathy / proteinuric CKD — ADA/KDIGO guidelines recommend ACE inhibitors in patients with diabetes, hypertension, and elevated urine albumin-to-creatinine ratio (≥30 mg/g). Evidence: High
Post-myocardial infarction (STEMI/NSTEMI) — Used to reduce ventricular remodelling and mortality when started within 24 hours of haemodynamic stabilisation. Evidence: High
Stable coronary artery disease — Supports vascular protection in high-risk patients. Evidence: Moderate
Post-transplant erythrocytosis — ACE inhibitors reduce erythropoietin-driven polycythaemia after renal transplantation. Evidence: Moderate
Dosing
Adult Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Hypertension — not on a diuretic | 5 mg PO once daily | 10–40 mg/day | 40 mg/day | Give once daily or divide BID if trough effect wanes Onset: 1 h; peak BP reduction: 4–6 h (FDA PI) |
| Hypertension — already on a diuretic | 2.5 mg PO once daily | 10–40 mg/day | 40 mg/day | Consider holding diuretic 2–3 days before starting, or monitor closely for first-dose hypotension |
| Heart failure (HFrEF) — standard | 2.5 mg PO BID | 10–20 mg PO BID | 20 mg BID (40 mg/day) | Titrate over weeks; usually combined with diuretic ± digoxin Monitor for ≥2 h after first dose |
| Heart failure — elevated creatinine (>1.6 mg/dL) or Na <130 mEq/L | 2.5 mg PO once daily | Titrate slowly q4 days | 40 mg/day | Requires close medical supervision; check renal function and potassium at each increase |
| Asymptomatic LV dysfunction (EF ≤35%) | 2.5 mg PO BID | 10 mg PO BID | 10 mg BID (20 mg/day) | Based on SOLVD Prevention trial dosing protocol |
| Hypertensive urgency — IV (enalaprilat) | 1.25 mg IV over ≥5 min q6h | 1.25–5 mg IV q6h | 5 mg IV q6h | Onset: ~15 min; convert to oral when able On diuretics: start 0.625 mg IV |
Pediatric Dosing (Age ≥1 Month to 16 Years)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Hypertension — pediatric | 0.08 mg/kg PO once daily (max 5 mg) | Titrate q2 weeks | 0.58 mg/kg/day (max 40 mg/day) | Not recommended if GFR <30 mL/min/1.73 m² Oral solution (1 mg/mL) preferred for younger children |
Renal Impairment Adjustments
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| CrCl >30 mL/min | No adjustment | Standard | 40 mg/day | Monitor renal function periodically |
| CrCl ≤30 mL/min or SCr ≥3 mg/dL | 2.5 mg PO once daily | Titrate to BP response | 40 mg/day | Enalaprilat accumulates when GFR falls below this threshold (FDA PI) |
| Haemodialysis | 2.5 mg PO on dialysis days | Adjust on non-dialysis days | 40 mg/day | Enalaprilat is dialysable (clearance ~62 mL/min) |
Clinical Pearl: First-Dose Hypotension
Patients most at risk include those who are volume-depleted, on high-dose diuretics, hyponatraemic, or have heart failure with low cardiac output. Consider withholding the diuretic for 2–3 days before the first dose of enalapril, or start with 2.5 mg under supervision. If once-daily dosing does not maintain blood pressure control over 24 hours, splitting into twice-daily dosing often resolves end-of-dose trough escape.
Pharmacology
Mechanism of Action
Enalapril is an oral prodrug that undergoes hepatic de-esterification by carboxylesterase 1 (CES1) to yield enalaprilat, a potent competitive inhibitor of angiotensin-converting enzyme (ACE). ACE catalyses the conversion of angiotensin I to the vasoconstrictor angiotensin II and also degrades the vasodilator bradykinin. By blocking this dual pathway, enalaprilat reduces circulating angiotensin II levels, decreases aldosterone secretion, and increases bradykinin activity. The net haemodynamic effect is a reduction in systemic vascular resistance with preservation or modest improvement in cardiac output. In heart failure, these actions decrease preload and afterload, reduce pulmonary capillary wedge pressure, and improve exercise tolerance. Unlike captopril, enalapril lacks a sulfhydryl moiety, which may account for a lower incidence of taste disturbance and rash.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | ~60% oral bioavailability; Tmax enalapril ~1 h, enalaprilat 3–4 h | Food does not affect absorption; can be taken without regard to meals |
| Distribution | Protein binding 50–60%; does not cross blood-brain barrier significantly | Limited CNS penetration; crosses placenta (drives fetal toxicity warning) |
| Metabolism | Hepatic hydrolysis by CES1 via OATP1B1 uptake; no CYP involvement; sole metabolite is enalaprilat | Minimal drug–drug interaction risk via CYP enzymes; no dose adjustment needed for hepatic impairment |
| Elimination | ~94% excreted in urine and faeces (40% as enalaprilat in urine); effective accumulation t½ 11 h; biphasic elimination (initial 2–6 h, terminal ~36 h) | Dose reduction required when CrCl ≤30 mL/min; dialysable (clearance 62 mL/min) |
Side Effects
≥10%
Very Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Increased serum creatinine | 20% | Typically mild and reversible; reflects haemodynamic reduction in glomerular filtration pressure rather than structural renal injury |
| Hypotension-related symptoms (SOLVD population) | 14.8% | Higher in heart failure patients; includes dizziness, lightheadedness, and syncope combined |
1–10%
Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Dizziness | 4.3–7.9% | Higher in heart failure trials (7.9% vs 0.6% placebo); often improves after first weeks of therapy |
| Headache | 5.2% | Similar rate to placebo (5.3%) in hypertension trials; rarely treatment-limiting |
| Fatigue | 2.8–5.8% | More prominent in the SOLVD population (5.8% vs 3.5% placebo); dose-related in some patients |
| Cough | 1.3–5.0% | Class effect of ACE inhibitors due to bradykinin accumulation; dry, non-productive, and persistent; switch to ARB if intolerable |
| Hypotension | 0.9–6.7% | 0.9% in hypertension trials; 6.7% in heart failure trials (vs 0.6% placebo) (FDA PI); risk highest with first dose, dehydration, or concurrent diuretics |
| Nausea | 1.3% | Usually mild and transient |
| Diarrhoea | 1.4% | Rarely requires discontinuation |
| Rash | 1.0% | Less frequent than with captopril; maculopapular pattern described |
| Syncope | 0.5–2.2% | 0.5% in hypertension, 2.2% in heart failure (FDA PI); higher when combined with diuretics (1.3% with HCTZ); volume repletion and slow titration reduce risk |
| Hyperkalemia | 1.2–3.8% | 1.2% in SOLVD (EF ≤35%); 3.8% in FDA PI heart failure trials; risk increases with renal impairment, diabetes, potassium-sparing diuretics, or potassium supplements |
Serious
Serious (Regardless of Frequency)
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Angioedema | 0.4–0.7% | Any time during therapy; most common after first doses | Immediately discontinue enalapril; secure airway; administer epinephrine if laryngeal involvement; permanent discontinuation of all ACE inhibitors |
| Acute renal failure | Rare | Days to weeks; higher risk with bilateral renal artery stenosis | Discontinue enalapril; volume resuscitation; evaluate for renovascular disease |
| Neutropenia / agranulocytosis | Rare | Weeks to months; higher risk with collagen vascular disease + renal impairment | Monitor WBC in high-risk patients; discontinue if neutropenia confirmed |
| Cholestatic jaundice progressing to hepatic necrosis | Very rare | Variable | Discontinue ACE inhibitor immediately; hepatology referral; potentially fatal if delayed |
| Anaphylactoid reactions | Very rare | During haemodialysis with high-flux membranes or LDL apheresis | Emergency treatment; avoid ACE inhibitors with high-flux dialysis membranes |
| Fetal toxicity | Expected with 2nd/3rd trimester exposure | Second and third trimesters | Discontinue immediately when pregnancy detected; fetal monitoring for renal function and amniotic fluid |
Discontinuation
Discontinuation Rates
Hypertension Trials
3.3% similar to placebo (FDA PI)
Top reasons: Cough, hypotension, headache, rash
Heart Failure / LVD Trials (SOLVD)
15.2% vs 8.6% placebo
Top reasons: Hypotension, cough, azotaemia, fatigue
| Reason for Discontinuation | Incidence in SOLVD (vs Placebo) | Context |
|---|---|---|
| Hypotension | 14.8% vs 7.1% | Most common contributor to discontinuation in heart failure; dose-related and more frequent in volume-depleted patients |
| Cough | 5.0% vs 2.0% | Class effect; resolves after discontinuation; ARB substitution recommended |
| Worsening renal function | 3.8% vs 1.6% | Higher risk with bilateral renal artery stenosis or severe heart failure with low perfusion pressure |
| Fatigue | 5.8% vs 3.5% | Often difficult to distinguish from underlying disease fatigue in heart failure |
Managing ACE Inhibitor Cough
Cough occurs in 1–5% of patients and is a class effect caused by increased bradykinin and substance P in the airways. It is characteristically dry, non-productive, and worse at night. Before attributing cough to enalapril, exclude other causes (heart failure decompensation, respiratory infection, GORD). If the cough is confirmed ACE inhibitor-related and intolerable, switching to an angiotensin receptor blocker (ARB) is the standard approach, as ARBs do not inhibit bradykinin degradation.
Drug Interactions
Enalapril is a prodrug activated by hepatic carboxylesterase 1 (CES1), not by cytochrome P450 enzymes, so CYP-mediated drug interactions are not a concern. The key interaction risks relate to additive effects on the renin-angiotensin-aldosterone system, potassium homeostasis, and renal haemodynamics.
Major
Aliskiren
MechanismDual RAS blockade
EffectIncreased risk of hypotension, hyperkalaemia, and acute renal failure
ManagementContraindicated in patients with diabetes; avoid if GFR <60 mL/min
FDA PI
Major
Potassium-Sparing Diuretics (spironolactone, eplerenone, amiloride)
MechanismAdditive potassium retention due to reduced aldosterone
EffectPotentially life-threatening hyperkalaemia
ManagementAvoid in heart failure unless closely monitored; check K⁺ within 1 week of initiation and after dose changes
FDA PI
Major
Sacubitril/Valsartan (Entresto)
MechanismDual neprilysin and ACE inhibition increases bradykinin
EffectElevated risk of angioedema
ManagementDo not co-administer; allow at least 36-hour washout when switching between agents
FDA PI / AHA 2022
Moderate
NSAIDs (ibuprofen, naproxen, celecoxib)
MechanismReduced prostaglandin-mediated renal vasodilation
EffectBlunted antihypertensive effect; increased risk of renal impairment and hyperkalaemia
ManagementUse lowest effective NSAID dose for shortest duration; monitor renal function and BP, especially in elderly or volume-depleted patients
FDA PI
Moderate
Lithium
MechanismReduced renal lithium clearance
EffectElevated serum lithium with risk of toxicity
ManagementMonitor lithium levels frequently when initiating, adjusting, or discontinuing enalapril
FDA PI
Moderate
ARBs (dual RAS blockade)
MechanismDual blockade of the renin-angiotensin system
EffectIncreased risk of hypotension, hyperkalaemia, and renal dysfunction without proven additional benefit in most populations
ManagementAvoid combination in general; if used, monitor BP, K⁺, and renal function closely
FDA PI / ONTARGET
Moderate
Potassium Supplements / Salt Substitutes
MechanismAdditive potassium load with reduced aldosterone-mediated excretion
EffectHyperkalaemia
ManagementUse with caution; monitor serum K⁺; advise patients about potassium-containing salt substitutes
FDA PI
Minor
Antidiabetic Agents (insulin, sulfonylureas)
MechanismACE inhibitors may improve insulin sensitivity
EffectPossible enhanced hypoglycaemic effect
ManagementMonitor blood glucose more closely during initiation and dose changes
LexicompMonitoring
-
Blood Pressure
Each visit; 2 h post first dose in HF
Routine Measure seated and standing BP at initiation and after each dose increase. In heart failure, observe for at least 2 hours after the first dose to detect symptomatic hypotension. -
Renal Function
Baseline, 1–2 weeks, then periodically
Routine Serum creatinine and BUN. A rise of up to 30% from baseline is often acceptable and haemodynamic; a rise >30% or progressive increase warrants dose reduction or discontinuation. Check more frequently in patients with pre-existing renal impairment or concurrent NSAIDs. -
Serum Potassium
Baseline, 1–2 weeks, after dose changes
Routine Risk of hyperkalaemia increases with renal impairment, diabetes, concurrent K⁺-sparing diuretics, or potassium supplements. Target K⁺ <5.5 mEq/L. -
White Blood Cell Count
Baseline, then periodically if high-risk
Trigger-based Recommended for patients with collagen vascular disease (SLE, scleroderma) and/or renal impairment, who are at higher risk for neutropenia. Monitor more frequently during the first 3 months. -
Hepatic Enzymes
If symptoms develop
Trigger-based Check ALT, AST, and bilirubin if patient develops jaundice or unexplained hepatic symptoms. ACE inhibitors have rarely been linked to cholestatic hepatitis progressing to hepatic necrosis. -
Pregnancy Status
Before starting and ongoing
Routine Confirm negative pregnancy test before initiating in women of childbearing potential. Counsel on reliable contraception and immediate reporting of pregnancy. Discontinue enalapril as soon as pregnancy is detected.
Contraindications & Cautions
Absolute Contraindications
- History of angioedema associated with any ACE inhibitor, or hereditary/idiopathic angioedema
- Hypersensitivity to enalapril, enalaprilat, or any ACE inhibitor
- Pregnancy (second and third trimesters; discontinue immediately when pregnancy detected)
- Concurrent aliskiren in patients with diabetes mellitus
- Concurrent sacubitril/valsartan (must allow 36-hour washout period)
Relative Contraindications (Specialist Input Recommended)
- Bilateral renal artery stenosis or stenosis of a solitary functioning kidney — high risk of acute renal failure; use only with nephrological oversight and close creatinine monitoring
- Haemodynamically significant aortic stenosis or hypertrophic obstructive cardiomyopathy — afterload reduction may precipitate critical hypotension and syncope
- Collagen vascular disease with renal impairment — elevated risk of neutropenia/agranulocytosis; requires frequent WBC monitoring
Use with Caution
- Volume depletion or hyponatraemia — correct dehydration before starting; consider lower initial dose and supervised first-dose administration
- Elderly patients — start at lower doses; higher baseline sensitivity to hypotension and renal effects
- Pre-existing renal impairment — dose adjustment required when CrCl ≤30 mL/min; monitor renal function more frequently
- High-flux haemodialysis membranes — risk of anaphylactoid reactions
- Patients undergoing desensitisation (e.g., hymenoptera venom) — increased anaphylactoid risk
- Patients scheduled for major surgery — discuss perioperative continuation vs. omission with anaesthesia team
FDA Boxed Warning
Fetal Toxicity
Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus. When pregnancy is detected, enalapril should be discontinued as soon as possible. Exposure during the second and third trimesters has been associated with fetal renal dysfunction, oligohydramnios, skull hypoplasia, limb contractures, lung hypoplasia, and neonatal death.
Patient Counselling
Purpose of Therapy
Enalapril works by blocking a hormone system that raises blood pressure and makes the heart work harder. Depending on the reason for prescribing, it may lower blood pressure, improve heart function, or protect the kidneys. It does not cure these conditions but controls them when taken consistently. Patients should continue taking enalapril even when feeling well and should never stop abruptly without discussing with their prescriber.
How to Take
Take enalapril at the same time each day, with or without food. If a dose is missed, take it as soon as remembered unless the next dose is due within a few hours. Do not double up to make up for a missed dose. Store at room temperature and keep away from moisture.
Dizziness & Lightheadedness
Tell patient
This is most likely in the first few days, especially when standing up from sitting or lying down. Rising slowly, staying well hydrated, and avoiding alcohol can help. The body usually adjusts within 1–2 weeks.
Call prescriber
If dizziness is severe, persistent beyond the first week, or if fainting occurs at any time.
Persistent Dry Cough
Tell patient
A dry, tickly cough is a recognised side effect that occurs in a small number of patients. It is not dangerous but can be bothersome. It usually stops within 1–4 weeks of discontinuation. Do not take cough suppressants without medical advice.
Call prescriber
If the cough is persistent and affecting sleep or daily activities; an alternative medication class (ARB) may be considered.
Swelling (Angioedema Warning)
Tell patient
Rarely, enalapril can cause swelling of the face, lips, tongue, or throat. This can occur at any time during treatment, not only when first starting.
Call prescriber
Seek emergency medical attention immediately if any swelling of the face, lips, tongue, or throat occurs, or if there is difficulty breathing or swallowing. Do not take another dose until assessed.
Pregnancy Prevention
Tell patient
Enalapril can cause serious harm to an unborn baby, especially in the second and third trimesters. Women of childbearing age should use reliable contraception throughout treatment.
Call prescriber
Report a positive pregnancy test or planned pregnancy immediately so that enalapril can be safely replaced with a pregnancy-compatible alternative.
Dehydration & Illness
Tell patient
Vomiting, diarrhoea, excessive sweating, or inadequate fluid intake can lead to a drop in blood pressure while on enalapril, causing dizziness or fainting. Stay well hydrated, especially in hot weather or during illness.
Call prescriber
If unable to keep fluids down for more than 24 hours, or if experiencing sustained dizziness or reduced urine output during illness.
Potassium Intake
Tell patient
Enalapril can raise potassium levels. Avoid potassium-containing salt substitutes (e.g., Lo-Salt) and do not take potassium supplements unless specifically instructed by a clinician.
Call prescriber
If experiencing muscle weakness, irregular heartbeat, or tingling in the extremities, as these may indicate elevated potassium.
Sources
Regulatory (PI / SmPC)
- Vasotec (enalapril maleate) tablets prescribing information. Merck & Co., Inc. Revised 2015. FDA Label Primary regulatory source for approved indications, dosing, adverse reactions, and contraindications.
- Epaned (enalapril maleate) oral solution prescribing information. Azurity Pharmaceuticals. Revised 2017. FDA Label Provides oral solution-specific formulation details and pediatric dosing information.
- Enalaprilat injection prescribing information. Dr. Reddy’s Laboratories Inc. Revised 2010. FDA Label Source for intravenous enalaprilat dosing, pharmacokinetics, and administration guidance.
Key Clinical Trials
- The SOLVD Investigators. Effect of enalapril on survival in patients with reduced left ventricular ejection fractions and congestive heart failure. N Engl J Med. 1991;325(5):293–302. doi:10.1056/NEJM199108013250501 Landmark trial establishing enalapril’s mortality benefit in symptomatic heart failure with EF ≤35%.
- The SOLVD Investigators. Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions. N Engl J Med. 1992;327(10):685–691. doi:10.1056/NEJM199209033271003 SOLVD Prevention trial showing enalapril reduces hospitalisation and delays progression to symptomatic heart failure.
- Kostis JB, Shelton B, Gosselin G, et al. Adverse effects of enalapril in the Studies of Left Ventricular Dysfunction (SOLVD). Am Heart J. 1996;131(2):350–355. doi:10.1016/S0002-8703(96)90365-8 Detailed adverse event analysis from both SOLVD arms; primary source for incidence rates in the LVD population.
- The CONSENSUS Trial Study Group. Effects of enalapril on mortality in severe congestive heart failure. N Engl J Med. 1987;316(23):1429–1435. doi:10.1056/NEJM198706043162301 First trial to demonstrate ACE inhibitor mortality reduction in NYHA Class IV heart failure.
Guidelines
- Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure. Circulation. 2022;145(18):e895–e1032. doi:10.1161/CIR.0000000000001063 Current guideline positioning ACE inhibitors including enalapril within guideline-directed medical therapy for HFrEF.
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. Hypertension. 2018;71(6):e13–e115. doi:10.1161/HYP.0000000000000065 Major hypertension guideline supporting ACE inhibitors as first-line agents in compelling indications including HF and CKD.
- de Boer IH, Khunti K, Sadusky T, et al. Diabetes management in chronic kidney disease: a consensus report by the ADA and KDIGO. Diabetes Care. 2022;45(12):3075–3090. doi:10.2337/dci22-0027 Joint guideline recommending ACE inhibitors for diabetic patients with albuminuria (ACR ≥30 mg/g).
Mechanistic / Basic Science
- Faruqi A, Jain A, Kwan E, et al. Enalapril. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated February 13, 2024. NCBI Bookshelf Comprehensive review of enalapril pharmacology, mechanism of action, adverse effects, and clinical considerations.
Pharmacokinetics / Special Populations
- Till AE, Gomez HJ, Hichens M, Bolognese JA. Enalapril clinical pharmacokinetics and pharmacokinetic-pharmacodynamic relationships: an overview. Clin Pharmacokinet. 1993;25(4):274–290. doi:10.2165/00003088-199325040-00003 Definitive PK review: bioavailability 60–70%, biphasic elimination, effective accumulation half-life 11 hours, and renal impairment effects.
- Inman WH, Rawson NS, Wilton LV, Pearce GL, Speirs CJ. Postmarketing surveillance of enalapril. I: Results of prescription-event monitoring. BMJ. 1988;297(6652):826–829. doi:10.1136/bmj.297.6652.826 Large post-marketing study (13,713 patients) documenting real-world adverse event frequencies including dizziness, cough, and angioedema.
- Smeets NJL, Litjens CHC, van den Heuvel JJMW, et al. Completing the enalaprilat excretion pathway: renal handling by the proximal tubule. Pharmaceutics. 2020;12(10):929. doi:10.3390/pharmaceutics12100929 Identifies OAT3 and OAT4 as renal transporters for enalaprilat, clarifying the renal excretion mechanism.