Capoten (Captopril) is an oral drug and a member of a class of drugs called angiotensin converting enzyme (ACE) inhibitors.
Mechanism of action:
Captopril and the other drugs in this class inhibit the converting enzyme peptidyl dipeptidase that hydrolyzes angiotensin I to angiotensin II and inactivates bradykinin, a potent vasodilator, which works at least in part by stimulating release of nitric oxide and prostacyclin. The hypotensive activity of captopril results both from an inhibitory action on the renin-angiotensin system and a stimulating action on the kallikrein-kinin system.
Captopril is used to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. It is also used to treat heart failure, protect the kidneys from harm due to diabetes, and to improve survival after a heart attack.
Side Effects:
Captopril generally is well tolerated, and side effects are usually mild and transient. A dry, persistent cough has been reported commonly with the use of captopril and other ACE inhibitors. Coughing resolves after discontinuing the drug. Other side effects include abdominal pain, constipation, diarrhea, rash, dizziness, fatigue, headache, loss of appetite, nauseas, fainting and numbness in the hands and feet.
Interactions:
The use of ACE inhibitors with potassium supplements, salt substitutes or diuretics, for example, spironolactone (Aldactone), that increase potassium in the blood may lead to excessive potassium levels (hyperkalemia). Potassium levels should be monitored whenever ACE inhibitors are used in combination with these drugs.
There have been reports of increased lithium (Eskalith, Lithobid) levels when lithium is used in combination with ACE inhibitors. The reason for this interaction is not known, but the increased levels may lead to toxicity from lithium.
Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, indomethacin and naproxen may reduce the effects of ACE inhibitors.
Combining captopril or other ACE inhibitors with nonsteroidal anti-inflammatory drugs (NSAIDs) in patients who are elderly, volume-depleted (including those on diuretic therapy), or with poor kidney function may result in reduced kidney function, including kidney failure. These effects are usually reversible.
Nitritoid reactions (symptoms include facial flushing, nausea, vomiting and low blood pressure) may occur when injectable gold (sodium aurothiomalate), used in the treatment of rheumatoid arthritis, is combined with ACE inhibitors, including captopril.
Contraindications:
Contraindicated during the second and third trimesters of pregnancy because of the risk of fetal hypotension, anuria and renal failure, sometimes associated with fetal malformations or deaths.
Captopril is secreted in breast milk. Therefore it should be avoided by nursing mothers.
Dosage for Captopril
The recommended dose of captopril for treating hypertension in adults is 25-150 mg two or three times daily.
The maximum dose is 450 mg daily. The dose for treating heart failure is 6.25 to 12.5mg every 8 hours.
The target dose is 50 mg every 8 hours and the maximum dose is 450 mg daily.
The dose for diabetic nephropathy is 25 mg every 8 hours.
How to use Captopril
Take this medication by mouth on an empty stomach (at least 1 hour before meals) as directed by your doctor, usually two to three times a day.
Other ACE Inhibitors
Enalapril is an oral prodrug that is converted by hydrolysis to a converting enzyme inhibitor enalaprilat, which effects like those of captopril. Enalaprilat itself is available only for intravenous use, primarily for hypertensive emergencies.
Lisinopril is a lysine derivative of enalaprilat. Benazepril, ramipril, perindopril, fosinopril, moexipril, quainapril and trandolapril are other long acting members of this class. All are prodrugs like enalapril and are converted to the active agents by hydrolysis, primarily in the liver.
