Captopril (Oral)

Captopril is an angiotensin-converting enzyme (ACE) medication used primarily to treat high blood pressure, although it can also be used to treat heart failure and improve kidney health in diabetics.


An angiotensin-converting enzyme (ACE) medication, captopril is most often used to improve high blood pressure. By using captopril to manage blood pressure, the risks of developing strokes and heart attacks are also reduced. Additionally, this ACE inhibitor can protect kidneys from diseases that generally develop in diabetics and improve recovery for heart attack victims. The drug works by improving blood flow throughout the body by relaxing the blood vessels.

In some people, a chemical called angiotensin II forms in the body and causes the blood vessels to contract by increasing growth in the surrounding muscles. ACE inhibitors interrupt the process initiated by angiotensin-converting enzymes, which helps to slow the production of angiotensin II. When blood flow is increased by the gradual enlargement of the blood vessels through captopril treatments, blood pressure is reduced, making it easier for the body to pump blood to the heart. While the benefit to a healthy heart is obvious, a heart in danger of failing can be helped immensely by the increased blood flow and may prevent failure.

Captopril has been available to patients since it was approved for human use by the U.S. Food and Drug Administration in 1981. Par Pharmaceutical Inc. manufactures the drug under the brand name of Capoten 25, though the generic version is also available.

Conditions treated

Type of medicine

  • ACE inhibitor

Side Effects

While these are the most commonly experienced side effects, other symptoms may develop and patients should be wary of any adverse reactions. The patient should report any negative effects from taking captopril to their doctor immediately, especially where side effects are experienced frequently or to a severe degree. Under such circumstances, the patient and doctor may be able to develop a way of reducing or eliminating the side effects through a reduction in captopril dose size, additional medications, or lifestyle changes.

Although side effects are rarely experienced, here are the most commonly observed side effects of taking captopril:

  • Chest pain or discomfort
  • Cloudy or bloody urine
  • Irregular or rapid pulse or heart rate
  • Pain in the arms, back, or jaw
  • Heaviness or tightness in the chest
  • Decreasing blood pressure
  • Changes in the ability to urinate, including an increase or decrease in the amount of urine produced
  • Neck veins are dilated
  • Excessive thirst
  • Difficulty breathing
  • Swelling that resembles hives, most commonly appearing on the face, around the eyelids, lips, tongue, and throat, or on the hands, legs, feet, or sexual organs
  • Loss of appetite
  • Pain in the lower back or on the sides
  • Nausea and/or vomiting
  • Cool feeling or paleness in the toes or fingertips
  • Sweating
  • Excessive tiredness or weariness
  • Unexplained weight gain

The following side effects were reported, though without a rate of frequency. As it's unknown how likely these adverse reactions are to occur, patients should still be aware of the possibility.

  • Blurry vision
  • Confusion
  • High fever
  • Bleeding of the gums or under the skin
  • Urination is difficult or painful
  • Red spots appearing on the skin
  • Paleness of the skin
  • Sore throat
  • Swollen glands
  • Stools that appear black, bloody, or tarry
  • Change in the taste of foods
  • Loss of taste
  • Skin feels warm to the touch
  • Itching skin
  • Chills
  • Redness in the face, neck, arms, or upper chest
  • Coughing
  • Feeling dizzy or lightheaded, especially when rising to sitting or standing position
  • Rash
  • Ulcers, sores, or white spots on the lips or in the mouth
  • Unexplained or unusual bleeding or bruising

Under dermatologic side effects, up to 13.1% of patients reported experiencing a rash, while under 10% of patients reported cases of pruritus and alopecia. Less commonly, only reported by 0.1% to 1% of patients, were incidences of angioedema. In very rare cases, patients reported developing urticaria, Stevens-Johnson syndrome, erythroderma, erythema multiforme, pemphigoid reactions, photosensitivity, and exfoliative dermatitis.

The most common gastrointestinal side effects patients taking captopril reported were nausea, accompanied by vomiting, and abdominal pain. Additionally, incidences of dry mouth, diarrhea, constipation, and gastric irritation were reported. Less common were cases of stomatitis/aphthous ulceration, mouth ulcers, and intestinal angioedema. In very rare instances, patients on captopril were diagnosed with glossitis, peptic ulcer, or pancreatitis, but these conditions occurred in just 0.01% of individuals.

Dizziness and a loss of taste or taste impairment affected up to 10% of patients. The nervous system was otherwise affected less commonly by incidences of paresthesia, drowsiness, cerebrovascular incidents, and headaches.

The most common respiratory side effects consisted of frequent coughing and dyspnea. Patients less commonly experienced bronchospasm, rhinitis, and allergic alveolitis or eosinophilic pneumonia, while taking the ACE inhibitor. Meanwhile, the cardiovascular system was most commonly affected by occurrences of hypotension in patients on the captopril treatments. Myocardial infarctions and congestive heart failure was also observed in patients, but at a much less common rate of frequency. Also rare but possible side effects include pastiness of the skin or a flushing, incidents of tachycardia or tachyarrhythmia, Raynaud's syndrome, angina pectoris, or heart palpitations. Cardiogenic shock and cardiac arrest is also possible but was reported in less than 0.01% of cases.

Psychiatric side effects were also reported by some patients while on the captopril drug. Sleep disorders were commonly reported in up to 10% of cases, while confusion, a loss of libido, and depression was reported in rare instances.

In some uncommon circumstances, the renal system was affected by occurrences of renal insufficiency, nephrotic syndrome, and acute renal failure. Likewise, the metabolic system was also affected, but in very rare instances. Side effects reported in this category were weight loss, anorexia, and loss of appetite.

Eyesight can be affected rarely. In cases where problems have occurred, patients reported experiencing disturbed vision, as well as dry and itchy eyes.

Some patients also experienced hematologic symptoms. The following side effects were reported in less than 0.01% of patients:

  • Neutropenia/agranulocytosis
  • Pancytopenia
  • Anemia
  • Thrombocytopenia
  • Lymphadenopathy
  • Eosinophilia
  • Decreased hemoglobin
  • Decreased hematocrit
  • Low leukocytes
  • Thrombocytes decreased
  • Elevated rates of erythrocyte sedimentation

Hepatic symptoms also occurred very rarely. Under this group, patients were sometimes found to have greater liver enzymes, elevated bilirubin levels, and impaired hepatic function. Additionally, patients in less than 0.01% of cases developed cholestasis or hepatitis. Jaundice also affected some patients, though the frequency of incidences could not be ascertained.

There were some immune system affectations reported, though in very rare cases. Also discovered in less than 0.01% of patients were incidences of autoimmune disease and positive antinuclear antibody titer. Additionally reported, but at an unknown rate, were cases of anaphylactoid reactions.

Rare musculoskeletal conditions found to affect patients undergoing captopril treatments were myalgia and arthralgia. Myasthenia was also discovered, though the frequency was not reported.

Captopril has been found to cause false test results in various medical exams. For this reason, the patient is advised to tell any doctor treating them that they're taking the drug. This will also help avoid prescriptions that could cause a severe reaction with captopril or render the treatment ineffective. Likewise, the patient should notify his or her doctor in the event of a necessary surgery. It may be necessary to stop taking captopril until the surgery has been done. Once the patient is out of recovery, he or she may resume taking the medication under his or her doctor's supervision.


In treating hypertension for adults, the initial dose should consist of 25 milligrams given orally 2 to 3 times daily. Each dose should be taken one hour before eating food. The maintenance dose may be increased at 1 to 2-week intervals, though the maximum dosage is 50 mg, given three times per day. In cases where blood pressure remains unaffected or hasn't shown a measured improvement, a dose of thiazide diuretic and titrate can be added to the treatment. The supplemental drugs should be increased to their maximum dosage, prior to increasing the captopril dosage.

When treating a patient for congestive heart failure, the initial dose should be 25 mg, administered orally three times a day. If the patient is either hypotensive, hyponatremic or hypovolemic, the dose should be reduced to 6.25 to 12.5 mg three times daily. The maintenance dose should be increased to 50 mg, given three times daily for a duration of one to two weeks. Once a positive response has been observed, treatment can be stopped. The patient should not receive more than 450 milligrams per day.

Captopril can also be used to treat left ventricular dysfunction. This condition can be treated with a dosage of 6.25 mg, given one time three days after a myocardial infarction. That dose should be followed by 12.5 mg three times daily, which is then increased to 25 mg over a period of several days. The target dose of 50 mg three times a day should be gradually achieved over the course of several weeks.

In treating a case of diabetic nephropathy, a 25 mg dose should be administered three times per day. Additional antihypertensive drugs can be used in conjunction with captopril, if blood pressure levels need greater reduction. This treatment is primarily intended for patients diagnosed with type I insulin-dependent diabetes mellitus and retinopathy.

Patients should be instructed to take doses of captopril at the same times every day to help limit the possibility of missing a dose. They should also be instructed to drink plenty of water throughout the treatment cycle to stay hydrated and reduce the risk of certain side effects, like diarrhea and vomiting. If the individual does miss a dose, he or she should take the dose as soon as possible. However, if it's nearing time for the next dose, the missed dose should be skipped to avoid doubling up on dosages. This could lead to an accidental overdose and require emergency medical treatment.

Additionally, the patient should be advised against taking salt substitutes or potassium supplements without the consent of the prescribing physician. Similarly, the patient should refrain from any alcohol consumption while being treated with captopril drug therapy.

Major Drug Interactions

Negative drug interactions are possible with any combination of medications, so it's important for patients to discuss their history with their doctor, prior to beginning captopril treatments. While it is important to discuss any prescription medications that the patient is taking, the individual should also share any nonprescription drugs he or she has been taking. While this includes over the counter medications, like heartburn drugs and sleeping pills, the patient should also mention any vitamins or herbal remedies that he or she has been taking. Equally important is a frank discussion about the patient's alcohol and recreational drug use. The patient should be advised to discontinue these practices while on the captopril drug therapy.

Below is a partial list of the drugs most commonly known to cause negative reactions, when combined with captopril treatments. Where a patient is specifically taking these medications, he or she should notify the prescribing doctor before beginning treatment.

  • Aliskiren
  • Amlodipine
  • Aliskiren
  • Allopurinol
  • Allopurinol
  • Amiloride
  • Hydrochlorothiazide
  • Aminophylline
  • Amlodipine
  • Valsartan
  • Olmesartan
  • Telmisartan
  • Azilsartan medoxomil
  • Chlorthalidone
  • Bisacodyl
  • Sodium biphosphate / sodium phosphate
  • Candesartan
  • Chlorpheniramine
  • Codeine
  • Phenylephrine
  • Potassium iodide
  • Citric acid
  • Potassium bicarbonate
  • Sodium bicarbonate
  • Potassium citrate
  • Sodium citrate
  • Ephedrine
  • Phenobarbital
  • Theophylline
  • Eprosartan
  • Irbesartan
  • Losartan
  • Olmesartan
  • Spironolactone
  • Telmisartan
  • Triamterene
  • Valsartan
  • Hyoscyamine
  • Methenamine
  • Methylene blue
  • Phenyl salicylate
  • Hyoscyamine
  • Iodine
  • Irbesartan
  • Iron dextran
  • Leflunomide
  • Lidocaine
  • Lomitapide
  • Losartan
  • LVP solution with potassium
  • Mipomersen
  • Mixed grass pollens allergen extract
  • Nebivolol
  • Valsartan
  • Olmesartan
  • Ragweed pollen allergen extract
  • Sacubitril
  • Valsartan
  • Spironolactone
  • Sulfamethoxazole
  • Trimethoprim
  • Telmisartan
  • Teriflunomide
  • Timothy grass pollen allergen extract
  • Tizanidine
  • Triamterene
  • Trimethoprim
  • Valsartan
  • Venetoclax

In the event that the patient wants to make any changes to his or medication schedule, the issue should be discussed with the doctor first. The caregiver responsible for prescribing captopril can advise the patient on starting, stopping, or changing the dosages of other medications, so it can be done safely and with a minimum of adverse reactions. Even a minor change implemented without proper medical advice can result in unwanted and possibly severe interactions.


Before starting captopril, discussing the patient's medical history is also an important step in determining treatment. Current and past medical conditions can have an effect on how the drug therapy interacts with the patient. Often, a new drug treatment can interact negatively with a medical condition, compromising the patient's overall health status.

The patient and doctor should also discuss any allergies. If the patient is allergic to any ACE inhibitors, he or she must notify their doctor, prior to treatment. These include any of the following:

  • Benazepril
  • Fosinopril
  • Enalapril
  • Lisinopril
  • Moexipril
  • Perindopril
  • Quinapril
  • Ramipril
  • Trandolapril

Additionally, captopril can negatively affect the patient, if she or he has been diagnosed with any of the following medical conditions:

In animal studies of captopril, unborn fetuses developed craniofacial malformations. Additionally, it has been found that drugs that interact with the renin-angiotensin system (RAS) during the second and third trimesters of pregnancy will likely cause neonatal and fetal morbidity and death, though there is no controlled data from research on human pregnancies. Captopril is therefore classified as a class D drug, meaning that it has caused, may cause, or is suspected to have caused human fetal malformations and/or irreversible fetal damage. The U.S. Food and Drug Administration adds that there is positive proof of human fetal risk, based on marketing or investigational experience.

Patients are also advised against breastfeeding, where the medication is necessary to the mother's health. If an alternative treatment will be equally effective and posed less of a risk to the breastfeeding infant, that method is preferred. Older infants may be breastfed, while the mother is taking captopril, but only when necessary. Breast milk has been tested in mothers taking captopril and the ACE inhibitor has been found in the milk.


Captopril should never be removed from the original container, except for doses about to be administered. Otherwise, keep it in the original bottle with the cap tightly screwed into place. The bottle should be stored at room temperature in a dry place, out of the reach of children. It should not be stored in the bathroom, as the humidity and moisture of the shower can affect the medication.

Additionally, it should be kept away from sources of excess heat.

It's especially important to arrange a storage place for medication that is out of the reach of both children and pets. Should the bottle be damaged or the cap inadvertently removed, a young child or a pet may swallow the medication. Under such circumstances, call for an ambulance immediately or contact your local poison control center.

When captopril is no longer needed or the prescription has expired, it must be disposed of immediately. To learn about the proper procedures for disposing of captopril, the patient should contact his or her caregiver. Trained medical personnel will be able to provide instructions on disposing or destroying the existing supply of medication.


Captopril can provide the best treatment for high blood pressure and hypertension, as well as helping patients recover from heart failure, as long as patients adhere to their physician's instructions. A trained caregiver is experienced in dealing with side effects brought about by the medication, so the patient is advised to seek their doctor's advice about any new conditions that arise. The doctor may be able to advise lifestyle changes or prescribe new medications to help manage or eliminate the adverse reactions.

In considering lifestyle changes, it is important for the patient to consult his or her doctor. While it may be presumed that a doctor will advise a healthier diet and more physical exercise, some medications limit how a patient can pursue these changes. For instance, some foods may cause adverse reactions when combined with the drug. Likewise, too much physical activity or strenuous exercises can cause severe reactions, while the patient is on certain medications.

Finally, it's important for the patient to maintain regular visits with the doctor, including keeping appointments for tests and screenings. When the patient begins canceling or missing appointments, the doctor loses his ability to keep track of the patient's progress. In the meantime, the patient may need a stronger dose of the medication or may be able to stop taking the drug altogether. By regularly consulting with the doctor, the patient can ensure he or she is getting the best possible treatment and the maximum results from taking captopril. The goal for both the doctor and the patient is to return the patient to an optimum state of health, which can be achieved through proper monitoring of the captopril drug treatments.

Last Reviewed:
December 25, 2017
Last Updated:
April 04, 2018