Captopril Drug Profile

What is Captopril?

Captopril is an oral medication belonging to the class of drugs known as ACE inhibitors (angiotensin-converting enzyme inhibitors). It is primarily prescribed to treat high blood pressure and heart failure by helping blood vessels relax and widen. Captopril was the first ACE inhibitor developed and remains an important treatment option for cardiovascular conditions.

Uses

Captopril is approved for several cardiovascular conditions:

• Hypertension (high blood pressure): Used alone or in combination with other medications to lower blood pressure and reduce the risk of stroke, heart attack, and kidney problems
• Heart failure: Helps improve heart function and reduce symptoms like shortness of breath and fluid retention in patients with weakened heart muscle
• Post-heart attack treatment: Prescribed after myocardial infarction to improve survival and prevent further heart damage
• Diabetic kidney disease: Used to slow the progression of kidney damage in patients with diabetes and protein in their urine
• Left ventricular dysfunction: Helps patients with reduced heart pumping function, even when they don’t have obvious heart failure symptoms

How it works

Captopril works by blocking the angiotensin-converting enzyme (ACE), which normally converts angiotensin I to angiotensin II, a powerful substance that causes blood vessels to narrow. By inhibiting this enzyme, captopril prevents the formation of angiotensin II, allowing blood vessels to relax and widen, which reduces blood pressure and decreases the workload on the heart. The medication also reduces the breakdown of bradykinin, a substance that helps dilate blood vessels.

Side effects

Common side effects include:

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• Dry cough (occurs in 10-20% of patients)
• Dizziness or lightheadedness, especially when standing up
• Fatigue or weakness
• Headache
• Nausea or upset stomach
• Skin rash or itching
• Metallic or altered taste sensation
• Low blood pressure

Serious side effects requiring immediate medical attention:

• Angioedema (swelling of face, lips, tongue, or throat)
• Severe kidney problems or kidney failure
• Dangerously high potassium levels (hyperkalemia)
• Severe allergic reactions
• Significant drop in white blood cell count

Warnings and precautions

• Pregnancy: Captopril should not be used during pregnancy, especially in the second and third trimesters, as it can cause serious harm or death to the developing fetus
• Kidney function: Patients with kidney disease require careful monitoring and possible dose adjustments, as captopril can worsen kidney function in some cases
• Potassium levels: Regular monitoring of blood potassium is necessary, as ACE inhibitors can cause dangerous elevations in potassium levels
• Dehydration: Patients should avoid becoming dehydrated, as this can lead to dangerously low blood pressure when combined with captopril
• Surgery: Patients should inform their surgeon and anesthesiologist about captopril use before any surgical procedures

Interactions

• Potassium supplements and salt substitutes: Can cause dangerous increases in blood potassium levels
• Diuretics: May cause excessive blood pressure lowering, especially when starting captopril
• NSAIDs (ibuprofen, naproxen): Can reduce captopril’s effectiveness and increase risk of kidney problems
• Lithium: Captopril can increase lithium levels in the blood, potentially causing toxicity
• Diabetes medications: May enhance blood sugar-lowering effects, requiring monitoring for hypoglycemia
• Aliskiren: Should not be used together in patients with diabetes or kidney problems
• Gold injections: May cause serious allergic reactions when combined with ACE inhibitors
• Alcohol: Can enhance the blood pressure-lowering effects and increase dizziness

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Dosage

Typical adult dosages vary depending on the condition being treated. For hypertension, the usual starting dose is 25 mg taken two to three times daily, which may be gradually increased to 50-100 mg two to three times daily based on blood pressure response. For heart failure, treatment typically begins with 6.25-12.5 mg three times daily, with gradual increases as tolerated. Maximum daily doses generally do not exceed 450 mg per day. Patients with kidney problems may require lower doses. All dosage adjustments should be made under the guidance of a healthcare provider, and blood pressure should be monitored regularly during treatment.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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