Cardura (Doxazosin) - Oral

What Is Cardura?

Cardura (doxazosin) is a drug used to treat the signs of an enlarged prostate, also known as benign prostatic hyperplasia (BPH). It is also used to lower high blood pressure. Doxazosin belongs to a class of drugs called alpha-1 blockers. It is available as immediate-release (IR) and extended-release (XL) tablets.

Cardura blocks specific receptors in your body, causing your veins and arteries to relax. It allows more effortless blood flow, which lowers blood pressure. Cardura also relaxes the bladder and prostate muscles, leading to lower BPH symptoms.

Drug Facts

Generic Name: Doxazosin
Brand Name: Cardura
Drug Availability: Prescription
Administration Route: Oral
Therapeutic Classification: Alpha-1 blockers
Available Generically: Yes
Controlled Substance: No
Active Ingredient: Doxazosin
Dosage Form(s): Immediate-release (IR) tablets, extended-release (XL) tablets

What Is Cardura Used For?

Cardura (doxazosin) is used to treat:

Although this drug lowers blood pressure, it is usually not the first drug preferred for blood pressure control. It is recommended to avoid using doxazosin in people designated female at birth and in older adults to lower high blood pressure.

How to Take Cardura

Immediate-Release

  • Take it daily with or without food in the morning or evening.
  • Some IR tablets are scored and may be cut in half with a pill cutter. Split the tablets only if your healthcare provider tells you to.

Extended-Release

  • Take it daily with breakfast. Swallow it whole. Do not break, crush, cut, or chew.
  • In your stool, you may notice something that looks like a tablet. This is normal and should not be seen as a cause for alarm. Consult your healthcare provider if you have any concerns.

Even if you feel OK, continue to take this medication as directed by your healthcare provider. Do not restart, adjust, or stop taking this medicine without talking to your healthcare provider.

Storage

Store at room temperature (77 F) in a dry place. You may store this drug during trips between cool and mildly hot (59 to 86 F) temperatures. Do not store it in a bathroom.

Keep all your medications in a safe spot, out of the reach of children and pets. 

Toss any unused or expired drugs. Avoid pouring unused and expired drugs down the drain or in the toilet. Ask your pharmacist or healthcare provider about the best ways to dispose of this medicine. Visit the FDA's website to know where and how to discard all unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications.

Off-Label Uses

Cardura is used off-label to eliminate kidney stones (ureteral calculi expulsion) and dysfunctional voiding in children 3 years and older. It also treats nightmares caused by post-traumatic stress disorder (PTSD).

How Long Does Cardura Take to Work?

Cardura IR and Cardura XL take 2 to 3 hours and 5 to 13 hours to peak in your body, respectively.

What Are the Side Effects of Cardura?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Doxazosin may cause little or no side effects in some people. If you have any concerns about any side effects, contact your healthcare provider. Some side effects of doxazosin are:

Severe Side Effects

Contact your healthcare provider immediately if you have any severe side effects. Dial 911 if you have a medical emergency or if your symptoms appear to be life-threatening. Serious side effects of Cardura include:

  • Chest pain that is new or worse
  • Swelling in the arms or legs
  • Terrible dizziness
  • Passing out
  • Shortness of breath
  • Painful erection that lasts more than four hours
  • Allergic reaction 
  • Long-lasting or severe cramps
  • Severe stomach pain or bloating

Report Side Effects

Cardura may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Cardura Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For benign enlargement of the prostate:
      • Adults—At first, 1 milligram (mg) once a day, in the morning or in the evening. Your doctor may increase your dose slowly up to 8 mg once a day.
    • For high blood pressure:
      • Adults—1 mg once a day to start. Your doctor may increase your dose slowly to as much as 16 mg once a day.
      • Children—Use and dose must be determined by your doctor.
  • For oral dosage form (extended-release tablets):
    • For benign enlargement of the prostate:
      • Adults—At first, 4 milligram (mg) once a day, in the morning with breakfast. Your doctor may increase your dose slowly up to 8 mg once a day.

Modifications

The following modifications should be kept in mind when using Cardura:

Severe allergic reaction: Avoid using Cardura if you have a known allergy to it or its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you're unsure.

Missed Dose

Take the missed dose once you remember. If it is close to your next dose, skip the missed dose and return to your usual dosing schedule. Do not take extra doses. If you missed a few days of taking this medication, consult your healthcare provider before starting it again.

Overdose: What Happens If I Use Too Much Cardura?

Overdose symptoms may include a severe drop in blood pressure.

What Happens If I Overdose on Cardura?

If you think you or someone else may have overdosed on Cardura, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Cardura, call 911 immediately.

Precautions

Drug Content Provided and Reviewed by IBM Micromedex®

It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly. This is especially important for elderly patients, who may be more sensitive to the effects of this medicine.

For patients taking this medicine for high blood pressure :

  • Do not take other medicines unless they have been discussed with your doctor. This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.

Dizziness, lightheadedness, or sudden fainting may occur after you take this medicine, especially when you get up from a lying or sitting position. These effects are more likely to occur when you take the first dose of this medicine. Taking the first dose at bedtime may prevent problems. However, be especially careful if you need to get up during the night. These effects may also occur with any doses you take after the first dose. Getting up slowly may help lessen this problem. If you feel dizzy, lie down so that you do not faint. Then sit for a few moments before standing to prevent the dizziness from returning.

The dizziness, lightheadedness, or sudden fainting is more likely to occur if you drink alcohol, stand for a long time, exercise, or if the weather is hot. While you are taking this medicine, be careful to limit the amount of alcohol you drink. Also, use extra care during exercise or hot weather or if you must stand for a long time.

Doxazosin may cause some people to become drowsy or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy, drowsy, or are not alert. After you have taken several doses of this medicine, these effects should lessen.

The possibility of priapism, a painful or prolonged erection of the penis, is a rare side effect that can occur when taking doxazosin and must have immediate medical attention.

What Are Reasons I Shouldn't Take Cardura? 

Avoid this drug if you are allergic to it, any part of its formulation, or drugs similar to it, like Hytrin (terazosin) or Minipress (prazosin).

What Other Medications Interact With Cardura?

Do not take doxazosin with other alpha-1 blockers. This combination can drastically drop your blood pressure, causing hypotension.

What Medications Are Similar?

Medications similar to Cardura that may be used to treat symptoms of an enlarged prostate include:

  • Uroxatral (alfuzosin)
  • Jalyn (dutasteride and tamsulosin)
  • Dibenzyline (phenoxybenzamine)
  • OraVerse (phentolamine) 
  • Minipress (prazosin)
  • Rapaflo (silodosin) 
  • Flomax (tamsulosin) 
  • Hytrin (terazosin)

This list contains drugs also prescribed to treat symptoms of enlarged prostate. It is NOT a list of medicines recommended to take with Cardura. Do not take these drugs together unless your healthcare provider tells you to. If you have any problems, talk to your healthcare provider.

Frequently Asked Questions

  • What is Cardura used to treat?

    Cardura is used to treat enlarged prostate symptoms and high blood pressure.

  • What are the common side effects of Cardura?

    The common side effects of Cardura are:

  • What should I do if I miss a dose of Cardura?

    Take the missed dose once you think of it. Skip the missed dose if it is close to your next dose, and then return to your regular dosing schedule. Do not take extra doses or double the amount. If you missed a few days of taking this medication, consult your healthcare provider before starting it again.

How Can I Stay Healthy While Taking Cardura?

In people designated male at birth, the chances of having benign prostatic hyperplasia (BPH) may increase with age. Hence, showing up at your yearly routine checkup is vital. 

If your healthcare provider prescribes this medicine, remember to check your blood pressure daily. Also, do not drive or do anything that requires staying alert for 24 hours after starting this medicine, increasing your dose, or restarting this medicine.

Moreover, if you are on a PDE-5 inhibitor, like Viagra (sildenafil), Cialis (tadalafil), or Levitra (vardenafil), taking Cardura with it may have an added effect on lowering blood pressure. If you've been sitting or lying down, carefully stand to reduce the risk of feeling dizzy or passing out. Take caution when going up and down the stairs.

Note: People designated female at birth are not supposed to use this medication. If you can get pregnant and are taking this medication, tell your healthcare provider if you're pregnant, planning to get pregnant, or breastfeeding.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Food and Drug Administration. Doxazosin.

  4. Bauer A. Dysfunctional voiding: update on evaluation and treatment. Current Opinion in Pediatrics. 2021;33(2):235-242. doi:10.1097/MOP.0000000000000980

  5. Food and Drug Administration. Cardura XL.