Capoten

Capoten (captopril) is an angiotensin-converting enzyme (ACE) inhibitor medication prescribed for the management of hypertension (high blood pressure), treatment of heart failure, and improvement of survival following a heart attack. It functions by relaxing blood vessels, allowing blood to flow more smoothly and the heart to pump more efficiently. This comprehensive guide provides detailed information for healthcare professionals and informed patients regarding its proper use, mechanism, and important safety considerations.

Features

• Active Ingredient: Captopril
• Drug Class: Angiotensin-converting enzyme (ACE) inhibitor
• Available Formulations: Oral tablets (12.5 mg, 25 mg, 50 mg, 100 mg)
• Mechanism of Action: Inhibits the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, leading to decreased aldosterone secretion
• Bioavailability: Approximately 60-75%; food reduces absorption by 30-40%
• Onset of Action: Antihypertensive effect begins within 15-60 minutes
• Peak Plasma Concentration: Reached within 60-90 minutes post-administration
• Elimination Half-Life: Less than 3 hours; hemodynamically effective half-life is longer due to binding to ACE
• Metabolism: Minimally hepatic
• Excretion: Primarily renal (>95%)

Benefits

• Effectively lowers elevated blood pressure, reducing the long-term risk of stroke, myocardial infarction, and kidney damage.
• Improves symptoms and survival rates in patients with congestive heart failure by decreasing cardiac afterload and preload.
• Provides cardioprotective benefits post-myocardial infarction, particularly in patients with left ventricular dysfunction.
• Offers a treatment option for diabetic nephropathy by reducing proteinuria and slowing the progression of renal disease.
• Can be used in combination therapy with other antihypertensive agents like thiazide diuretics for synergistic effects.

Common use

Capoten is primarily indicated for the treatment of hypertension, either as monotherapy or in combination with other antihypertensive agents. It is also a cornerstone in the management of congestive heart failure, often used alongside diuretics and digitalis. A significant application includes its use in hemodynamically stable patients within the first 24 hours post-myocardial infarction to improve survival. Furthermore, it is prescribed for the management of diabetic nephropathy (macroalbuminuria) in patients with insulin-dependent diabetes mellitus.

Dosage and direction

Dosage must be individualized based on the patient’s clinical condition and renal function.

For Hypertension:

• Initial dose: 25 mg twice daily or three times daily.
• Maintenance dose: May be increased to 50 mg twice daily or three times daily after 1-2 weeks. Dosage may be further increased at intervals of at least 2 weeks up to a maximum of 450 mg daily.
• Diuretic-treated patients: Initiate therapy at 6.25 mg or 12.5 mg twice daily to minimize the risk of hypotension.

For Heart Failure:

• Initial dose: 6.25 mg or 12.5 mg three times daily under close medical supervision.
• Target maintenance dose: 50 mg three times daily, titrated upward as tolerated.

Post-Myocardial Infarction:

• Therapy may be initiated as early as 3 days post-infarction.
• Initial dose: 6.25 mg, followed by 12.5 mg three times daily.
• Target dose: Increase to 25 mg three times daily over the next several days, and then to a target of 50 mg three times daily over the following several weeks.

Administration: Administer orally one hour before meals for optimal and consistent absorption. Dosage adjustments are necessary for patients with renal impairment.

Precautions

• Hypotension: Symptomatic hypotension, sometimes severe, may occur following the initial dose, especially in volume-depleted patients (e.g., those on diuretic therapy). Correct volume and salt depletion prior to administration, if possible.
• Impaired Renal Function: Use with caution in patients with renal insufficiency. Monitor renal function before and during therapy. Dose adjustment is required.
• Hyperkalemia: Elevations in serum potassium may occur. Risk is increased in patients with renal impairment, diabetes, or those concomitantly using potassium-sparing diuretics, potassium supplements, or salt substitutes containing potassium.
• Cough: A persistent, dry, non-productive cough has been reported with ACE inhibitor use and may necessitate discontinuation of therapy.
• Surgery/Anesthesia: Capoten may potentiate the effects of hypotension-inducing agents used during anesthesia. It is often recommended to discontinue ACE inhibitors 24 hours prior to major surgery.
• Neutropenia/Agranulocytosis: Although rare, this serious side effect is more common in patients with collagen vascular disease or renal impairment. Monitor white blood cell counts in patients at risk.

Contraindications

• Known hypersensitivity to captopril or any other ACE inhibitor.
• History of angioedema related to previous ACE inhibitor therapy.
• Concomitant use with aliskiren in patients with diabetes.
• Second and third trimester of pregnancy (can cause injury and even death to the developing fetus).

Possible side effect

Common side effects are often dose-related and may include:

• Rash (often maculopapular, with pruritus)
• Cough (dry, persistent)
• Taste disturbance (dysgeusia) or loss of taste (ageusia)
• Gastrointestinal disturbances (nausea, vomiting, diarrhea, stomach pain)
• Dizziness or lightheadedness, particularly with the first few doses
• Fatigue

Serious side effects requiring immediate medical attention include:

• Angioedema (swelling of the face, lips, tongue, throat, larynx, or extremities)
• Symptomatic hypotension
• Jaundice or signs of hepatotoxicity
• Signs of infection (e.g., fever, sore throat - possible neutropenia)
• Signs of renal impairment (e.g., oliguria, edema)
• Hyperkalemia

Drug interaction

• Diuretics: Potentiates hypotensive effect. Risk of first-dose hypotension.
• Potassium-Sparing Diuretics (e.g., spironolactone, amiloride) / Potassium Supplements: Increased risk of hyperkalemia.
• Lithium: Increased serum lithium levels and lithium toxicity.
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): May diminish the antihypertensive effect and increase the risk of renal function deterioration.
• Gold Injections (sodium aurothiomalate): Nitritoid reactions (flushing, nausea, dizziness, hypotension) have been reported.
• Oral Hypoglycemics and Insulin: Captopril may increase hypoglycemic effect.
• Aliskiren: Concomitant use is contraindicated in patients with diabetes due to increased risk of renal impairment, hyperkalemia, and hypotension.

Missed dose

If a dose is missed, it should be taken as soon as possible. However, if it is almost time for the next scheduled dose, the missed dose should be skipped. Do not double the dose to make up for a missed one.

Overdose

The most likely manifestation of an overdose is severe hypotension. Other signs may include bradycardia, electrolyte disturbances, and shock. Management is primarily supportive and includes volume expansion with intravenous normal saline to restore blood pressure. Captopril is removed by hemodialysis.

Storage

Store at room temperature (15°-30°C or 59°-86°F) in a tightly closed container. Protect from moisture. Keep out of reach of children. Do not use after the expiration date printed on the container.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here.

Reviews

• “Captopril remains a fundamental agent in our cardiology toolkit. Its rapid onset and proven efficacy in heart failure and post-MI management are invaluable, though we remain vigilant for the first-dose hypotensive effect.” – Cardiologist, 15 years experience
• “An effective and cost-conscious choice for hypertension. The need for multiple daily dosing can be a compliance challenge for some patients compared to newer once-daily ACE inhibitors, but its efficacy is well-established.” – General Practitioner
• “As a nephrologist, I find its role in reducing proteinuria in diabetic patients to be crucial. Careful monitoring of potassium and renal function is paramount for safe use in this population.” – Nephrologist
• “The side effect profile, particularly the dry cough, sometimes necessitates a switch to an ARB. However, for many patients, it is a well-tolerated and highly effective therapy.” – Clinical Pharmacist