PRILOTEN 5

Indications

• Hypertension
• Heart failure
• Asymptomatic left ventricular dysfunction

Dosage

Children: Refer to the B

Adults: Refer to the BNF for specific dosing recommendations.

Mechanism of action

Enalapril acts by inhibiting the enzyme ACE, which is responsible for the conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and stimulates aldosterone secretion from the adrenal glands, leading to sodium and water retention. By blocking this pathway, enalapril decreases the levels of angiotensin II, resulting in vasodilation and reduced blood pressure. The drug also enhances bradykinin levels, which contribute to vasodilation and may mediate some of the drug's beneficial cardiovascular effects.

Pharmacodynamics

The antihypertensive effects of enalapril are observed within 1 to 2 hours after oral administration, with peak effects occurring at around 4 to 6 hours. Its maximum effect can last up to 24 hours, allowing for once-daily dosing in many cases. The overall reduction in blood pressure is due to decreased peripheral vascular resistance and decreased cardiac output due to the drug's impact on fluid retention and vascular tone. Enalapril also improves symptoms of heart failure and reduces morbidity and mortality associated with left ventricular dysfunction.

Pharmacokinetics

Enalapril is well absorbed after oral administration, with peak plasma concentrations occurring 1 hour after ingestion. It undergoes extensive first-pass metabolism to its active form, enalaprilat. The bioavailability is approximately 60%, and the half-life of enalaprilat is about 11 hours. Enalapril is primarily excreted by the kidneys, and dosage adjustments may be necessary in patients with renal impairment. It is not significantly metabolized by the liver, making it a suitable option for patients with hepatic dysfunction.

Contra-indications

• Hypersensitivity to enalapril or any of its components
• History of angioedema related to previous ACE inhibitor treatment
• Severe renal impairment
• Pregnancy
• Concurrent use with aliskiren in patients with diabetes

Adverse effects

• Cough
• Hyperkalemia
• Hypotension
• Angioedema
• Renal impairment
• Rash
• Dizziness
• Fatigue

Interactions

• Potassium-sparing diuretics may increase the risk of hyperkalemia
• Nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the antihypertensive effect
• Lithium levels may increase due to decreased clearance
• Other antihypertensive agents may have additive effects leading to hypotension

Precautions

• Use with caution in patients with renal artery stenosis
• Monitor renal function periodically during treatment
• Caution in patients with a history of heart failure
• Consider dose adjustment in elderly patients or those with renal impairment

Pregnancy

Enalapril is contraindicated during pregnancy due to the risk of fetal harm, particularly during the second and third trimesters.

Breast-feeding

Enalapril is excreted in breast milk, and caution is advised when administering to nursing mothers.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Tablets: 2.5 mg, 5 mg, 10 mg, 20 mg
• Oral solution