Captopril belongs to the group of medications known as ACE inhibitors. It is used to treat high blood pressure, congestive heart failure, and diabetic nephropathy (kidney problems caused by diabetes). Captopril is also used to improve survival after a heart attack. It works by relaxing blood vessels and making the heart pump more efficiently.

Captopril may be used in addition to other blood pressure medications, such as a diuretic (water pill) like hydrochlorothiazide, when one medication has not been found to satisfactorily control blood pressure or congestive heart failure.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual starting dose of captopril depends on the condition for which you are taking this medication.

For treating high blood pressure, the usual starting dose is 25 mg taken by mouth 2 or 3 times a day. After 1 or 2 weeks, your doctor may increase your dose, depending on side effects and how well the medication is working for you. The dose of captopril to control blood pressure does not usually go above 50 mg 3 times daily. The maximum dose of captopril is 450 mg daily given in 3 equally divided doses.

For treating heart failure, the usual starting dose is 25 mg taken by mouth 2 or 3 times a day. After 1 or 2 weeks, your doctor may increase your dose, depending on side effects and how well the medication is working for you. The dose of captopril to treat heart failure does not usually go above 50 mg to 100 mg given 3 times daily. The maximum dose of captopril is 450 mg daily given in 3 divided doses.

After a heart attack, the usual starting dose is 12.5 mg taken by mouth, 3 times a day. This dose will be increased gradually, to the recommended daily dose of 50 mg taken 3 times a day.

When treating kidney disease caused by diabetes, the recommended dose is 25 mg taken by mouth, 3 times daily. If this dose does not adequately lower blood pressure, other medications will be used in addition to captopril. Captopril should be taken 1 hour before meals.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take this medication if you:

• are allergic to captopril or any ingredients of the medication
• are pregnant
• have experienced angioedema (a serious allergic reaction that causes the area around the face, throat, and tongue to swell) after taking any of the class of medications known as ACE inhibitors (e.g., captopril, enalapril, fosinopril, lisinopril, etc.)
• have diabetes or kidney disease and are taking aliskiren

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• changed sense of taste
• constipation
• cough (dry, persistent)
• decreased ability or interest in sexual activity
• diarrhea
• dry mouth
• flushing
• headache
• loss of appetite
• mouth sores
• nausea
• trouble sleeping
• unusual tiredness
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain, abdominal distention
• chest pain
• dizziness, lightheadedness, or fainting (signs of low blood pressure)
• fast or pounding heartbeat
• signs of heart problems (e.g., fast, irregular heartbeat or pulse, chest pain, sudden weight gain, difficulty breathing, leg swelling)
• increased frequency of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of kidney problems (e.g., change in the amount or colour of urine, increased urination at night, blood in the urine, swelling in the feet or legs)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• skin rash (with or without itching)
• vision changes

Signs of too much potassium in the body:

• confusion
• irregular heartbeat
• nervousness
• numbness or tingling in the hands, feet, or lips
• shortness of breath or difficulty breathing
• weakness or heaviness in the legs

Stop taking the medication and seek immediate medical attention if any of the following occur:

• difficulty swallowing or breathing (sudden)
• fever and chills
• hoarseness
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of angioedema (e.g., swelling of the face, mouth, hands, or feet)
• signs of heart attack (e.g., sudden chest pain or pain radiating to back, down arm, jaw; sensation of fullness of the chest; nausea; vomiting; sweating; anxiety)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Angioedema: Angioedema (a serious allergic reaction that causes the area around the throat and tongue to swell) may occur with the use of ACE inhibitors, including captopril. This occurs for about 1 in 1,000 people. If you experience swelling of the face, tongue, or throat, stop taking captopril at once and seek immediate medical attention. People who have had angioedema caused by other substances may be at increased risk of angioedema while taking an ACE inhibitor.

Cough: People taking captopril may develop a dry, persistent cough that usually disappears only after stopping or lowering the captopril dose. Be sure to tell your doctor of any cough that does not seem to be related to a usual cause.

Fluid and electrolyte levels: Increases in blood levels of potassium occur for a small percentage of people who take captopril. This rarely causes problems, but your doctor should monitor your potassium levels. People with kidney disease or diabetes are at a higher risk of having increased blood potassium while taking captopril.

Infection: Captopril can reduce the number of cells that fight infection in the body (white blood cells). Tell your doctor immediately if you notice signs of an infection, such as fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness. Your doctor will do blood tests regularly to monitor the number of specific types of blood cells in your blood.

Report any signs of infection, such as sore throat or fever, to your doctor.

Kidney function: Changes in kidney function have been seen in certain people taking this medication. The use of diuretics (water pills) or aliskiren may further increase the risk of kidney problems for those already at risk for this problem. If you have kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Let your doctor know if you notice any decrease in urine output or increased swelling of the lower limbs, which suggests an accumulation of fluid due to decreased urination.

Liver function: Changes in liver function have occurred in people with or without preexisting liver problems during treatment with this medication. In most cases, the changes were reversed when the medication was stopped. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Low blood pressure: Occasionally, blood pressure drops too low after taking captopril. This usually happens after the first or second dose or when the dose is increased. It is more likely to occur for those who take aliskiren or water pills, have a salt-restricted diet, are on dialysis, are suffering from diarrhea or vomiting, or have been sweating excessively and not drinking enough liquids. Get up slowly when rising from a sitting or lying down position. If low blood pressure causes you to faint or feel lightheaded, contact your doctor.

Excessive sweating and lack of fluid intake may lead to an excessive fall in blood pressure because of reduced fluid in your blood vessels. Vomiting or diarrhea may also lead to a fall in blood pressure. Consult your doctor if you feel your blood pressure is too low.

Surgery: If you are scheduled to have any type of surgery, inform all the doctors involved in your care that you are taking captopril.

Pregnancy: ACE inhibitors such as captopril may cause severe harm or death to the developing baby if taken by the mother during pregnancy. This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Small amounts (1%) of captopril are passed from the mother to the infant in breast milk. The effect of this amount on the breast-fed child has not been determined. Talk to your doctor about whether you should breast-feed while taking this medication.

Children: The safety and effectiveness of using this medication have not been established for children.

There may be an interaction between captopril and any of the following:

• acetylsalicylic acid (ASA)
• aldesleukin
• aliskiren
• allopurinol
• alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• alpha agonists (e.g., clonidine, methyldopa)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
• antacids (e.g., aluminum hydroxide, calcium carbonate, magnesium hydroxide, sodium bicarbonate)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• apomorphine
• azathioprine
• barbiturates (e.g., butalbital, phenobarbital)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• bismuth subsalicylate
• bortezomib
• brimonidine
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• celecoxib
• conivaptan
• dexmethylphenidate
• diazoxide
• diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
• drospirenone
• duloxetine
• eplerenone
• everolimus
• "gliptin" diabetes medications (DPP-IV inhibitors; e.g., linagliptin, saxagliptin, sitagliptin)
• grass pollen allergen extract
• guanfacine
• heparin
• iron sucrose
• lanthanum
• levodopa
• lithium
• low-molecular-weight heparins (e.g., dalteparin, enoxaparin, tinzaparin)
• magnesium supplements
• medications that increase potassium levels (e.g., potassium supplements, spironolactone, amiloride, triamterene, and salt substitutes containing potassium)
• metformin
• methylphenidate
• minoxidil
• morphine
• nabilone
• nitrates (e.g., nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
• non-steroidal anti-inflammatory medications (NSAIDs; e.g., diclofenac, ibuprofen, naproxen)
• obinutuzumab
• other angiotensin converting enzyme inhibitors (ACEIs; enalapril, ramipril)
• pentoxifylline
• phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pregabalin
• rasagiline
• riociguat
• ropinirole
• rotigotine
• sacubitril
• selegiline
• sirolimus
• sodium phosphates
• tacrolimus
• temsirolimus
• tizanidine
• tolvaptan
• tranylcypromine
• tretinoin
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• trimethoprim
• yohimbine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.