Captopril

Drug Information: Captopril

Captopril is an angiotensin-converting enzyme (ACE) inhibitor used primarily for the treatment of hypertension. It works by blocking the ACE enzyme, preventing the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. Captopril helps lower blood pressure, improve heart function, and protect the kidneys, making it a valuable medication for managing various cardiovascular and renal conditions. It is also used in the management of heart failure and diabetic nephropathy.

Category

Antihypertensive

Mechanism of Action

Captopril is an angiotensin-converting enzyme (ACE) inhibitor. ACE is a crucial enzyme in the renin-angiotensin-aldosterone system (RAAS), a hormonal system that regulates blood pressure and fluid balance. ACE converts angiotensin I to angiotensin II, a potent vasoconstrictor that also stimulates the release of aldosterone from the adrenal glands. Aldosterone promotes sodium and water retention by the kidneys, further increasing blood volume and blood pressure.

By inhibiting ACE, Captopril prevents the formation of angiotensin II. This leads to several beneficial effects:

• Vasodilation: Reduced angiotensin II levels cause blood vessels to relax (vasodilation), decreasing peripheral vascular resistance and lowering blood pressure.
• Reduced Aldosterone: Lower angiotensin II also results in decreased aldosterone secretion. This promotes sodium and water excretion by the kidneys, further reducing blood volume and blood pressure.
• Increased Bradykinin: ACE also breaks down bradykinin, a vasodilator. By inhibiting ACE, Captopril increases bradykinin levels, contributing to vasodilation.
• Improved Endothelial Function: ACE inhibitors like Captopril may also improve endothelial function, the health of the inner lining of blood vessels, contributing to long-term cardiovascular benefits.

In summary, Captopril lowers blood pressure by inhibiting ACE, leading to vasodilation, reduced aldosterone secretion, increased bradykinin levels, and improved endothelial function, ultimately reducing the workload on the heart and improving cardiovascular health.

Clinical Uses

Captopril is primarily used in the treatment and management of various cardiovascular and renal conditions, including:

• Hypertension: Captopril is effective in lowering blood pressure in patients with essential or secondary hypertension. It can be used alone or in combination with other antihypertensive agents, such as diuretics.
• Heart Failure: Captopril is a valuable medication for managing heart failure by reducing afterload and improving cardiac output. It helps alleviate symptoms such as shortness of breath and edema.
• Diabetic Nephropathy: In patients with diabetes, Captopril can slow the progression of kidney disease by reducing proteinuria and protecting the glomerular filtration rate.
• Left Ventricular Dysfunction after Myocardial Infarction (MI): Captopril is used to improve survival and reduce the risk of heart failure in patients who have experienced a myocardial infarction and have left ventricular dysfunction.
• Hypertensive Crisis: In certain cases, Captopril can be used to rapidly lower blood pressure in hypertensive emergencies under close medical supervision.

Its ability to lower blood pressure, reduce cardiac workload, and protect the kidneys makes it a cornerstone in the management of these conditions. Regular monitoring of blood pressure, kidney function, and electrolytes is essential during Captopril therapy.

Dosage

The dosage of Captopril varies depending on the condition being treated and the individual patient’s response. Below are general guidelines; always consult with a healthcare professional for personalized dosage instructions.

Adults:

• Hypertension: The initial dose is typically 12.5 mg two or three times daily. The dosage can be gradually increased to 25-50 mg two or three times daily, as needed, up to a maximum of 150 mg per day.
• Heart Failure: The initial dose is usually 6.25 mg three times daily. The dosage can be increased gradually to a maximum of 50 mg three times daily, as tolerated.
• Diabetic Nephropathy: The typical dose is 25 mg three times daily.

Pediatrics:

• The recommended starting dose is 0.3 mg/kg three times daily. Dosage can be titrated based on blood pressure response, not to exceed 6 mg/kg/day in divided doses. Use in pediatric patients should be carefully monitored by a physician experienced in treating hypertension in children.

Route of Administration: Captopril is administered orally. It is typically taken two to three times daily, usually one hour before meals as food can reduce its absorption.

Indications

Captopril is indicated for the treatment of:

• Hypertension (high blood pressure)
• Heart failure
• Diabetic nephropathy (kidney disease in diabetics)
• Left ventricular dysfunction following myocardial infarction

Contraindications

Captopril is contraindicated in the following conditions:

• Hypersensitivity to Captopril or any other ACE inhibitor
• History of angioedema related to previous ACE inhibitor treatment
• Pregnancy (especially during the second and third trimesters)
• Concomitant use with aliskiren in patients with diabetes mellitus or renal impairment (GFR < 60 mL/min)

FAQ

Q1: What is Captopril used for?

A1: Captopril is primarily used to treat hypertension (high blood pressure), heart failure, and diabetic nephropathy. It may also be used after a heart attack to improve heart function.

Q2: How does Captopril work?

A2: Captopril works by blocking an enzyme called angiotensin-converting enzyme (ACE). This prevents the production of angiotensin II, a substance that narrows blood vessels. By blocking ACE, Captopril helps to relax blood vessels and lower blood pressure.

Q3: What are the common side effects of Captopril?

A3: Common side effects include dizziness, fatigue, cough, nausea, and loss of taste. Some people may also experience a skin rash.

Q4: Can Captopril be taken with other medications?

A4: Captopril can interact with other medications, such as diuretics, potassium supplements, and NSAIDs. It’s essential to inform your doctor about all medications you are taking.

Q5: Is Captopril safe during pregnancy?

A5: No, Captopril is contraindicated during pregnancy, especially in the second and third trimesters, as it can cause serious harm to the fetus.

Q6: How should Captopril be taken?

A6: Captopril should be taken as prescribed by your doctor, usually two to three times a day. It is often recommended to take it one hour before meals, as food can reduce its absorption.

Q7: What should I do if I miss a dose of Captopril?

A7: If you miss a dose, take it as soon as you remember. However, if it’s almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.

Q8: How long does it take for Captopril to start working?

A8: Captopril usually starts to lower blood pressure within one to two hours after taking it. However, it may take several weeks to achieve the full therapeutic effect, especially when treating conditions like heart failure.