CAPTOPRIL
(kap'toe-pril)
Capoten
Classifications: cardiovascular agent; angiotensin-converting enzyme (ace) inhibitor; antihypertensive agent
Prototype: Enalapril
Pregnancy Category: D

Availability

12.5 mg, 25 mg, 50 mg, 100 mg tablets

Actions

Lowers blood pressure by specific inhibition of the angiotensin-converting enzyme (ACE). This interrupts conversion sequences initiated by renin that lead to formation of angiotensin II, a potent endogenous vasoconstrictor. ACE inhibition alters hemodynamics without compensatory reflex tachycardia or changes in cardiac output (except in patients with CHF). Peripheral vascular resistance is lowered by vasodilation. Inhibition of ACE also leads to decreased circulating aldosterone. Reduced circulating aldosterone is associated with a potassium-sparing effect. In heart failure, captopril administration is followed by a fall in CVP and pulmonary wedge pressure; hypotensive action appears to be unrelated to plasma renin levels.

Therapeutic Effects

Effective in stepped protocol management of hypertension to convert to normotensive range, and in congestive heart failure with resulting decreases in dyspnea and improved exercise tolerance.

Uses

Hypertension; in conjunction with digitalis and diuretics in CHF, diabetic nephropathy, left ventricular dysfunction post MI.

Unlabeled Uses

Idiopathic edema.

Contraindications

Angioedema, hypersensitivity to captopril or ACE inhibitors; hypotension; pregnancy (category D), lactation.

Cautious Use

Impaired renal function, patient with solitary kidney; collagen-vascular diseases (scleroderma, SLE); patients receiving IMMUNOSUPPRESSANTS or other drugs that cause leukopenia or agranulocytosis; autoimmune disease, bone marrow suppression, coronary or cerebrovascular disease; cardiomyopathy, aortic stenosis; severe salt/volume depletion; heart failure, renal artery stenosis, renal disease, renal failure, renal impairment; hyperkalemia, children, elderly.

Route & Dosage

Hypertension
Adult: PO 6.25–25 mg t.i.d., may increase to 50 mg t.i.d. (max: 450 mg/d)
Child: PO 0.3–12.5 mg/kg q12–24h, may titrate up to max of 6 mg/kg/d in 2–4 divided doses
Infant: PO 0.15–0.3 mg/kg, may titrate up to 6 mg/kg/d in 1–4 divided doses
Neonate: PO 0.05–0.1 mg/kg q8–24 h, may titrate up to 0.5 mg/kg q6–24 h
Premature infant: PO 0.01 mg/kg q8–12h

Congestive Heart Failure
Adult: PO 6.25–12.5 mg t.i.d., may increase to 100 mg t.i.d. (max: 450 mg/d)

Renal Insufficiency
Clcr 10–50 mL/min = 75% of dose, Clcr <10 mL/min = 50% of dose

Administration

Oral

Adverse Effects (1%)

Body as a Whole: Hypersensitivity reactions, serum sickness-like reaction, arthralgia, skin eruptions. CV: Slight increase in heart rate, first dose hypotension, dizziness, fainting. GI: Altered taste sensation (loss of taste perception, persistent salt or metallic taste); weight loss, intestinal angioedema. Hematologic: Hyperkalemia, neutropenia, agranulocytosis (rare). Respiratory: cough. Skin: Maculopapular rash, urticaria, pruritus, angioedema, photosensitivity. Urogenital: Azotemia, impaired renal function, nephrotic syndrome, membranous glomerulonephritis. Other: Positive antinuclear antibody (ANA) titers.

Diagnostic Test Interference

In some patients, elevated urine protein levels may persist even after captopril has been discontinued. Possibility of transient elevations of BUN and serum creatinine, slight increase in serum potassium, and serum prolactin, increases in liver enzymes, and false-positive urine acetone (using sodium nitroprusside reagent). Captopril may decrease fasting blood sugar in the nondiabetic and cause hypoglycemia in the diabetic patient controlled with antidiabetic drug therapy.

Interactions

Drug: nitrates, diuretics, and antihypertensives enhance hypotensive effects. Aspirin and other nsaids may antagonize hypotensive effects. potassium-sparing diuretics (spironolactone, amiloride) increase potassium levels. Probenecid decreases elimination and increases effects. Food: Food decreases absorption; take 30–60 min before meals.

Pharmacokinetics

Absorption: 60–75% absorbed; food may decrease absorption 25–40%. Onset: 15 min. Peak: 1–2 h. Duration: 6–12 h. Distribution: Distributed to all tissues except CNS; crosses placenta. Metabolism: Some liver metabolism. Elimination: Excreted primarily in urine; excreted in breast milk.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education


Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug