What it's for (Indications)
- Captopril is used for the treatment of mild to moderate hypertension (high blood pressure).
- Its beneficial effects also extend to heart failure, primarily resulting from suppression of the renin-angiotensin-aldosterone system.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | Dosage must be individualized. Captopril should be taken one hour before meals. For hypertension, the initial dose is typically 25 mg two or three times daily. If satisfactory blood pressure reduction is not achieved after one to two weeks, the dose may be increased to 50 mg two or three times daily. The usual maximum dose for hypertension does not exceed 50 mg three times daily. If blood pressure is not satisfactorily controlled at this dose, a modest dose of a thiazide-type diuretic (e.g., hydrochlorothiazide) may be considered. Concomitant sodium restriction may be beneficial. |
Safety & Warnings
Common Side Effects
- Reported side effects include neutropenia/agranulocytosis (low levels of white blood cells), hypotension (low blood pressure), and rash (often with pruritus, sometimes with fever, arthralgia, and eosinophilia; typically maculopapular and rarely urticarial).
- Loss of taste, proteinuria, renal insufficiency, renal failure, nephrotic syndrome, polyuria, oliguria, urinary frequency, anemia, thrombocytopenia, and pancytopenia have also been reported.
Serious Warnings
- Black Box Warning: WARNING: FETAL TOXICITY. When pregnancy is detected, discontinue captopril as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus.
- Captopril is not recommended during breastfeeding.
- Patients should use caution and avoid driving or operating heavy machinery if the medicine affects their ability, as it may cause dizziness or lightheadedness.
- Caution is advised in patients with kidney impairment due to the risk of renal insufficiency, renal failure, nephrotic syndrome, and proteinuria.
- Use with caution in patients with collagen vascular disease (connective tissue disease).
- Severe hematologic reactions such as neutropenia/agranulocytosis have occurred.
How it Works (Mechanism of Action)
The mechanism of action of captopril involves the inhibition of Angiotensin-Converting Enzyme (ACE), a peptidyldipeptide carboxy hydrolase. This inhibition prevents the conversion of angiotensin I to angiotensin II, a potent endogenous vasoconstrictor. By suppressing the renin-angiotensin-aldosterone system, captopril reduces vasoconstriction, decreases aldosterone secretion (thereby minimizing sodium and fluid retention), and contributes to blood pressure reduction.