Captopril-Drug-Study

 

Captopril (Capoten) is an ACE inhibitor and a common antihypertensive. Captopril works by competitively inhibiting the conversion of angiotensin I to angiotensin II.

Generic Name

captopril

Brand Names

  • Apo-Capto (CAN),
  • Capoten,
  • Gen-Captopril (CAN),
  • Novo-Captopril (CAN),
  • Nu-Capto (CAN)

Classification

ACE inhibitor, Antihypertensive

  • Pregnancy Category C (first trimester)
  • Pregnancy Category D (second and third trimesters)

Dosage & Route

  • PO HTN Initial: 12.5 mg twice daily.
    • Maintenance: 25-50 mg twice daily.
    • Max: 50 mg 3 times/day.
  • Heart failure Initial: 6.25-12.5 mg 2-3 times/day.
    • Max: 50 mg 3 times/day.
  • Post MI Start 3 days after MI.
    • Initial: 6.25 mg/day, may increase after several wk to 150 mg/day in divided doses if needed and tolerated.
  • Diabetic nephropathy 25 mg 3 times/day.

Therapeutic actions

  • Captopril competitively inhibits the conversion of angiotensin I (ATI) to angiotensin II (ATII), thus resulting in reduced ATII levels and aldosterone secretion. It also increases plasma renin activity and bradykinin levels. Reduction of ATII leads to decreased sodium and water retention. By these mechanisms, captopril produces a hypotensive effect and a beneficial effect in congestive heart failure.

Pharmacokinetics

  • Absorption: 60-75% absorbed from the GI tract (oral); peak plasma concentrations after 1 hr. Absorption may be reduced in the presence of food.
  • Distribution: Protein-binding: 30%; crosses the placenta and enters breast milk at about 1% of maternal blood concentrations.
  • Excretion: Via urine (40-50% as unchanged, the rest as disulfide and other metabolites); 2-3 hr (elimination half-life), may be increased in renal impairment. Removed by hemodialysis.

Indications

  • Treatment of hypertension alone or in combination with thiazide-type diuretics
  • Treatment of CHF in patients unresponsive to conventional therapy; used with diuretics and digitalis
  • Treatment of diabetic nephropathy
  • Treatment of left ventricular dysfunction after MI
  • Unlabeled uses: Management of hypertensive crises; treatment of rheumatoid arthritis; diagnosis of anatomic renal artery stenosis, hypertension related to scleroderma renal crisis; diagnosis of primary aldosteronism, idiopathic edema; Bartter’s syndrome; Raynaud’s syndrome

Adverse effects

  • Hypotension, tachycardia, chest pain, palpitations, pruritus, hyperkalemia. Proteinuria; angioedema, skin rashes; taste disturbance, nonproductive cough, headache.
  • Potentially Fatal: Neutropenia, usually occurs within 3 mth of starting therapy especially in patients with renal dysfunction or collagen diseases. Hyperkalaemia. Anaphylactic reactions.

Contraindications

  • Known hypersensitivity to the drug.
  • Bilateral renal artery stenosis,
  • hereditary angioedema;
  • renal impairment;
  • pregnancy.

Nursing Considerations

Assessment

  • History: Allergy to captopril, history of angioedema, impaired renal function, CHF, salt or volume depletion, pregnancy, lactation
  • Physical: Skin color, lesions, turgor; T; P, BP, peripheral perfusion; mucous membranes, bowel sounds, liver evaluation; urinalysis, LFTs, renal function tests, CBC and differential

Interventions

  • Administer 1 hr before meals.

[box type="note"]WARNING: Ensure that patient is not pregnant before beginning treatment. Encourage use of contraceptives; if pregnancy is detected, stop drug.[/box]

[box type="note"]WARNING: Alert surgeon and mark patient’s chart with notice that captopril is being taken; the angiotensin II formation subsequent to compensatory renin release during surgery will be blocked; hypotension may be reversed with volume expansion.[/box]

  • Monitor patient closely for fall in BP secondary to reduction in fluid volume (due to excessive perspiration, and dehydration, vomiting, or diarrhea); excessive hypotension may occur.
  • Reduce dosage in patients with impaired renal function.

Teaching points

  • Take drug 1 hour before meals; do not take with food. Do not stop without consulting your healthcare provider.
  • Be careful of drop in blood pressure (occurs most often with diarrhea, sweating, vomiting, or dehydration); if lightheadedness or dizziness occurs, consult your healthcare provider.
  • Severe fetal damage can occur if captopril is taken during pregnancy. Use of contraceptives is advised; if pregnancy should occur, stop drug and notify health care provider.
  • Avoid over-the-counter medications, especially cough, cold, allergy medications that may contain ingredients that will interact with ACE inhibitors. Consult your healthcare provider.
  • You may experience these side effects: Cough, GI upset, loss of appetite, change in taste perception (limited effects, will pass); mouth sores (frequent mouth care may help); rash; fast heart rate; dizziness, light-headedness (usually passes after the first few days; change position slowly, and limit your activities to those that do not require alertness and precision).
  • Report mouth sores; sore throat, fever, chills; swelling of the hands or feet; irregular heartbeat, chest pains; swelling of the face, eyes, lips or tongue; difficulty breathing.

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