Enalapril

1. Introduction

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor used to treat hypertension, heart failure, and certain kidney conditions. By inhibiting ACE, it reduces the formation of angiotensin II, a vasoconstrictor, leading to relaxation of blood vessels and reduced blood pressure. Enalapril also helps reduce the workload on the heart and protects kidney function in specific conditions.

2. Indications

  • Approved Indications:
    • Hypertension (essential and renovascular hypertension).
    • Heart failure (to improve symptoms and reduce hospitalisations).
    • Asymptomatic left ventricular dysfunction.
  • Off-Label Uses:
    • Diabetic nephropathy (to delay progression of kidney disease).
    • Post-myocardial infarction (to improve survival).

3. Dosage

  • Adults:
    • Hypertension: Start with 5 mg once daily. Maintenance dose: 10–20 mg daily, divided into one or two doses. Maximum: 40 mg/day.
    • Heart Failure: Start with 2.5 mg once daily. Gradually titrate to 10–20 mg daily in divided doses.
    • Asymptomatic Left Ventricular Dysfunction: 2.5 mg twice daily, increasing to 10 mg twice daily as tolerated.
  • Children (≥1 month):
    • Initial dose: 0.08 mg/kg once daily (maximum initial dose: 5 mg).
    • Maintenance dose: Up to 0.58 mg/kg/day (maximum: 40 mg/day).
  • Elderly:
    • Start with the lowest effective dose (2.5 mg once daily) due to increased sensitivity.

4. Administration

  • Take orally with or without food.
  • Consistent timing (e.g., morning or evening) is recommended to optimise blood pressure control.

5. Forms Available

  • Tablets: 2.5 mg, 5 mg, 10 mg, 20 mg.
  • Oral solution: 1 mg/mL (for paediatric and special populations).

6. Side Effects

6.1. Common Side Effects

  • Dizziness.
  • Cough (dry, persistent).
  • Fatigue.
  • Headache.

6.2. Less Common Side Effects

  • Nausea.
  • Muscle cramps.
  • Rash.

6.3. Rare but Serious Side Effects

  • Angioedema (swelling of the face, lips, or tongue).
  • Hyperkalaemia (high potassium levels).
  • Kidney dysfunction (increased creatinine or urea).

7. Warnings

  • Angioedema: Rare but potentially life-threatening. More common in Black patients and those with a history of ACE inhibitor-induced angioedema.
  • Hypotension: May occur, particularly after the first dose in patients with volume depletion (e.g., diuretics, heart failure).
  • Hyperkalaemia: Risk increases when used with potassium supplements or potassium-sparing diuretics.

8. Precautions

  • Avoid use in patients with a history of angioedema related to previous ACE inhibitor use.
  • Use cautiously in patients with severe renal impairment or bilateral renal artery stenosis.
  • Monitor renal function and potassium levels regularly, especially in patients with diabetes or kidney disease.

9. Interactions

  • Drug-Drug Interactions:
    • Potassium-sparing diuretics (e.g., spironolactone): Increased risk of hyperkalaemia.
    • NSAIDs: May reduce the antihypertensive effect and increase the risk of kidney dysfunction.
    • Lithium: Increased risk of lithium toxicity.
    • Other antihypertensives (e.g., diuretics, beta-blockers): Additive hypotensive effect.
  • Drug-Food Interactions:
    • Avoid high-sodium diets, as they may reduce the antihypertensive efficacy.

10. Monitoring Parameters

  • Blood pressure and symptoms of hypotension, particularly after the first dose or dose adjustments.
  • Kidney function (e.g., serum creatinine, eGFR) and potassium levels.
  • Signs of angioedema or persistent cough.

11. Use in Children

  • Approved for use in children ≥1 month old for hypertension. Dose adjustments are required based on weight and renal function.

12. Use in Pregnancy

  • Category D: Contraindicated in pregnancy due to the risk of foetal toxicity (e.g., kidney damage, oligohydramnios).

13. Use in Elderly

  • Start at lower doses due to increased risk of hypotension and renal impairment.

14. Use in Kidney Disease

  • Dose adjustments are required in renal impairment:
    • CrCl 30–80 mL/min: Start with 5 mg/day.
    • CrCl 10–30 mL/min: Start with 2.5 mg/day.
    • CrCl <10 mL/min: Use with caution and start with 2.5 mg on alternate days.

15. Use in Liver Disease

  • Use with caution, as enalapril is metabolised to its active form (enalaprilat) in the liver.

16. Patient Counselling Points

  • Take enalapril at the same time each day, and do not skip doses.
  • Inform your doctor if you experience swelling, persistent cough, or dizziness.
  • Avoid potassium supplements or salt substitutes containing potassium unless directed by your doctor.
  • Stay hydrated, but avoid excessive fluid intake if you have heart failure.
  • Inform healthcare providers that you are on enalapril before any surgery or procedure.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
VasotecMerck & Co.$20–40 (30 tablets, 10 mg)
Generic EnalaprilVarious$5–15 (30 tablets, 10 mg)
RenitecMerck Sharp & Dohme$25–50 (30 tablets, 10 mg)

18. FAQs

  1. What is enalapril used for?
    Enalapril is used to treat high blood pressure, heart failure, and certain kidney conditions.
  2. How does enalapril work?
    It blocks ACE, reducing the production of angiotensin II, which helps lower blood pressure and relax blood vessels.
  3. What are the common side effects of enalapril?
    Common side effects include dizziness, fatigue, and a dry, persistent cough.
  4. Can enalapril cause swelling?
    Yes, angioedema (swelling of the face, lips, or tongue) is a rare but serious side effect.
  5. How should enalapril be taken?
    Take it orally, with or without food, at the same time each day.
  6. Can enalapril be taken during pregnancy?
    No, it is contraindicated during pregnancy due to the risk of foetal harm.
  7. Does enalapril interact with other medications?
    Yes, it interacts with potassium-sparing diuretics, NSAIDs, and lithium, among others.
  8. What should I do if I miss a dose of enalapril?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up.
  9. Can enalapril cause low blood pressure?
    Yes, especially after the first dose or in patients who are dehydrated or on diuretics.
  10. Can enalapril be used in children?
    Yes, it is approved for hypertension in children ≥1 month old, with dose adjustments based on weight.
  11. How long does enalapril take to work?
    Blood pressure reduction is usually noticeable within a few hours, with maximum effect seen in 1–2 weeks.
  12. Can enalapril cause kidney problems?
    Rarely, it can cause kidney dysfunction, especially in patients with renal artery stenosis or dehydration.
  13. What should I avoid while taking enalapril?
    Avoid potassium supplements and salt substitutes containing potassium unless directed by a doctor.
  14. Is enalapril safe for elderly patients?
    Yes, but start at a lower dose due to increased sensitivity to side effects.
  15. How should enalapril be stored?
    Store at room temperature, away from moisture and heat.