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 Name | Manufacturer | Price (USD) |
---|---|---|
Vasotec | Merck & Co. | $20–40 (30 tablets, 10 mg) |
Generic Enalapril | Various | $5–15 (30 tablets, 10 mg) |
Renitec | Merck Sharp & Dohme | $25–50 (30 tablets, 10 mg) |
18. FAQs
- What is enalapril used for?
Enalapril is used to treat high blood pressure, heart failure, and certain kidney conditions. - How does enalapril work?
It blocks ACE, reducing the production of angiotensin II, which helps lower blood pressure and relax blood vessels. - What are the common side effects of enalapril?
Common side effects include dizziness, fatigue, and a dry, persistent cough. - Can enalapril cause swelling?
Yes, angioedema (swelling of the face, lips, or tongue) is a rare but serious side effect. - How should enalapril be taken?
Take it orally, with or without food, at the same time each day. - Can enalapril be taken during pregnancy?
No, it is contraindicated during pregnancy due to the risk of foetal harm. - Does enalapril interact with other medications?
Yes, it interacts with potassium-sparing diuretics, NSAIDs, and lithium, among others. - 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. - Can enalapril cause low blood pressure?
Yes, especially after the first dose or in patients who are dehydrated or on diuretics. - Can enalapril be used in children?
Yes, it is approved for hypertension in children ≥1 month old, with dose adjustments based on weight. - 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. - Can enalapril cause kidney problems?
Rarely, it can cause kidney dysfunction, especially in patients with renal artery stenosis or dehydration. - What should I avoid while taking enalapril?
Avoid potassium supplements and salt substitutes containing potassium unless directed by a doctor. - Is enalapril safe for elderly patients?
Yes, but start at a lower dose due to increased sensitivity to side effects. - How should enalapril be stored?
Store at room temperature, away from moisture and heat.