Nurses Compass
Drug Guide
Captopril
Classification
Therapeutic: Antihypertensive, ACE inhibitor
Pharmacological: Angiotensin-Converting Enzyme (ACE) Inhibitor
FDA Approved Indications
- Hypertension
- Heart failure
- Diabetic nephropathy
Mechanism of Action
Captopril inhibits angiotensin-converting enzyme, reducing the formation of angiotensin II, leading to vasodilation, decreased blood pressure, and reduced aldosterone secretion.
Dosage and Administration
Adult: Typically 25 mg two to three times daily, titrated based on response.
Pediatric: Dosage varies; usually initiated at 0.12-0.5 mg/kg/dose two times daily and adjusted as needed.
Geriatric: Start at lower doses due to increased sensitivity, monitor renal function and electrolytes.
Renal Impairment: Dose adjustment needed; typically reduce dose or increase dosing interval.
Hepatic Impairment: Use with caution; no specific dose adjustments but monitor closely.
Pharmacokinetics
Absorption: Well absorbed orally, with about 75% bioavailability.
Distribution: Wide distribution, crosses the placenta.
Metabolism: Minimal hepatic metabolism; some conjugation occurs.
Excretion: Primarily excreted unchanged in urine.
Half Life: 2 to 4 hours.
Contraindications
- History of angioedema related to previous ACE inhibitor therapy.
- Bilateral renal artery stenosis.
- Hypersensitivity to captopril or other ACE inhibitors.
Precautions
- Pregnancy (category D), especially in second and third trimesters.
- Renal impairment, hyperkalemia, hypotension, collagen vascular disease, especially systemic lupus erythematosus.
Adverse Reactions - Common
- Cough (Common)
- Elevated blood potassium (hyperkalemia) (Common)
- Hypotension (Common)
Adverse Reactions - Serious
- Angioedema (Rare but serious)
- Neutropenia/agranulocytosis (Rare)
- Renal failure (Rare)
Drug-Drug Interactions
- Diuretics, especially potassium-sparing (risk of hyperkalemia)
- Other antihypertensives (additive effect)
- Potassium supplements, potassium-containing salt substitutes
- NSAIDs (reduce antihypertensive effect and risk of renal impairment)
Drug-Food Interactions
- Potassium-rich foods (risk of hyperkalemia)
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor blood pressure, renal function, electrolytes, and for signs of angioedema.
Diagnoses:
- Risk for injury related to hypotension or angioedema.
- Electrolyte imbalance.
Implementation: Administer on an empty stomach 1 hour before meals or 2 hours after. Monitor BP and labs regularly.
Evaluation: Assess BP response, renal function, and electrolyte levels periodically.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report signs of angioedema (swelling of face, lips, tongue, or throat).
- Avoid potassium-rich foods and supplements unless directed.
- Monitor blood pressure regularly.
Special Considerations
Black Box Warnings:
- Potential for fetal injury and death when used during pregnancy.
- Angioedema risk.
Genetic Factors: Genetic predisposition may influence drug metabolism and adverse effects.
Lab Test Interference: May increase serum potassium and serum creatinine; monitor accordingly.
Overdose Management
Signs/Symptoms: Severe hypotension, dizziness, fainting, electrolyte disturbances.
Treatment: Discontinue drug, restore blood pressure with IV fluids, and administer vasopressors if necessary. Dialysis may be required in severe cases.
Storage and Handling
Storage: Store at room temperature, away from moisture and heat.
Stability: Stable for 2-3 years when stored properly.