Uses

What is doxazosin used for?

Doxazosin is commonly used to treat benign prostatic hyperplasia (BPH), a condition where the prostate gland is enlarged but not cancerous. An enlarged prostate may lead to problems with urination (peeing). 

Doxazosin is also commonly used to treat high blood pressure (hypertension).

Doxazosin may also be used for other conditions as determined by your healthcare provider.

How does doxazosin work (mechanism of action)?

Doxazosin is an alpha blocker. It works to relax certain muscles in your body.

For BPH, doxazosin works to relax certain muscles in your prostate and bladder. This improves the flow of urine and reduces the symptoms of BPH.

For high blood pressure, doxazosin works to relax certain muscles in your blood vessels. This makes your blood vessels more open and lets blood move through them more easily, which lowers blood pressure.

How is doxazosin supplied (dosage forms)?

Doxazosin is available as Cardura, Cardura XL, and generic doxazosin in the following dosage forms that are taken by mouth.

  • 1 mg oral tablets
  • 2 mg oral tablets
  • 4 mg oral tablets
  • 8 mg oral tablets
  • 4 mg extended-release tablets
  • 8 mg extended-release tablets

How should I store doxazosin?

Doxazosin should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of doxazosin?

The most common side effects of doxazosin are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Tiredness or feeling weak
  • Headache
  • Dizziness

There may be other side effects of doxazosin that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of doxazosin?

While less common, the most serious side effects of doxazosin are described below, along with what to do if they happen.

Severe Allergic Reactions. Doxazosin may cause allergic reactions, which can be serious. Stop using doxazosin and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Low Blood Pressure Upon Standing (Orthostatic Hypotension). Doxazosin may cause a sudden drop in blood pressure when standing up from a seated or lying position. This may result in fainting, especially when you first start doxazosin. To help prevent this side effect, your healthcare provider may tell you to take your first dose of doxazosin at bedtime. Tell your healthcare provider right away if you have any of the following symptoms of orthostatic hypotension.

  • Dizziness, feeling lightheaded, or fainting upon standing
  • Blurred vision
  • Confusion
  • Feeling weak
  • Feeling like your heart is racing or skipping (palpitations)

Painful, Prolonged Erection (Priapism). Doxazosin may cause an unwanted erection that is persistent, painful, and that may occur without sexual arousal. Priapism may cause permanent damage to the penis. Stop taking doxazosin and get emergency help right away if you have any of the following symptoms. 

  • Erection lasting for more than 4 hours 
  • Erection that is unrelated to sexual stimulation
  • Painful or tender penis

Chest Pain (Angina). Doxazosin may cause chest pain. Chest pain can also be a symptom of a heart attack. Stop taking doxazosin and get emergency help right away if you have any of the following symptoms of a heart attack.

  • Chest pain or pressure
  • Fast or abnormal heartbeat
  • Trouble breathing
  • Pain in your back, jaw, throat, or arm
  • Sweating, upset stomach, vomiting, or dizziness

Warnings & Precautions

Who should not take doxazosin?

Allergies to Ingredients. People who are allergic to any of the following should not use doxazosin.

  • Cardura
  • Cardura XL
  • Doxazosin
  • Doxazosin mesylate
  • A medicine known as a quinazoline, such as prazosin or terazosin
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific doxazosin products they stock.

What should I know about doxazosin before taking it?

Do not take doxazosin unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share doxazosin with other people, even if they have the same condition as you. It may harm them.

Keep doxazosin out of the reach of children.

Do not chew, cut, or crush doxazosin extended-release tablets.

Doxazosin may cause dizziness. Do not drive or do other activities that require coordination for 24 hours after your first dose or after your dose is increased. Wait to drive or do other activities that require coordination until you know how doxazosin affects you.

People who are age 65 and older can be at greater risk for some side effects from doxazosin. Talk to your healthcare provider about your risks if you are in this age group.

Doxazosin is commonly used to treat benign prostatic hyperplasia (BPH), which is non-cancerous enlargement of the prostate. In some cases, BPH can occur at the same time as prostate cancer. Your healthcare provider may recommend getting tested for prostate cancer before you start doxazosin and getting regular screenings thereafter. 

What should I tell my healthcare provider before using doxazosin?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if doxazosin is right for you.

In particular, make sure that you discuss any of the following.

Severe Liver Problems. If your liver is not working as well as it should be, you may be at higher risk for side effects of doxazosin, such as low blood pressure. If there is a concern about the health of your liver, your healthcare provider may do tests to determine if it is working well enough to take this medicine.

Heart Problems. Doxazosin may cause or worsen chest pain (angina). This risk may be higher in people with existing heart disease. Tell your healthcare provider if you have heart problems such as heart failure or a recent heart attack. Your healthcare provider can determine if doxazosin is safe for you.

Planned Eye Surgery. Doxazosin may raise the risk of eye problems called intraoperative floppy iris syndrome during or after cataract or glaucoma surgery. Tell your healthcare provider if you are planning to have eye surgery. They may recommend that you wait until after the surgery is over to start doxazosin.

Other Medicines and Supplements. Doxazosin may interact with other medicines and supplements. Before using doxazosin, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Narrow Digestive Tract. Doxazosin extended-release tablets may not be safe for people with a problem in their digestive tract that causes narrow areas (strictures). Your healthcare provider can determine if a different form of this medicine is safe for you.

Pregnancy. It is not known if doxazosin could affect pregnancy or if it could harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant. Your healthcare provider will advise you if you should take doxazosin while you are pregnant or trying to get pregnant.

Breastfeeding. It is not known if doxazosin passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed.

Interactions

Does doxazosin interact with foods or drinks?

There are no known interactions between doxazosin and foods or drinks.

Doxazosin extended-release tablets should be taken with breakfast each day. Taking this medicine with a meal and at the same time each day helps it work effectively.

It is unknown if drinking alcohol will affect doxazosin. The risk of side effects, such as dizziness, may be higher if you drink alcohol while taking doxazosin.

Does doxazosin interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking doxazosin. 

  • A medicine for high blood pressure
  • A type of medicine called a phosphodiesterase-5 (PDE-5) inhibitor, such as avanafil (Stendra), sildenafil (Viagra, Revatio, and others), tadalafil (Cialis and others), or vardenafil (Levitra, Staxyn), which are used for erectile dysfunction and pulmonary arterial hypertension (PAH)
  • Clarithromycin (Biaxin XL), which is a medicine used for bacterial infections
  • An antiviral medicine for HIV, such as ritonavir (Norvir)
  • A medicine for fungal infections, such as itraconazole (Sporanox) or ketoconazole (Nizoral)

This may not be a complete list of medicines that can interact with doxazosin. Always check with your healthcare provider.

Does Doxazosin (Cardura) interact with other drugs you are taking?
Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much doxazosin?

If you or someone else has used too much doxazosin, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of doxazosin?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses. 

If you miss doses of doxazosin for a few days in a row, check with your healthcare provider before taking it again. They may recommend a lower dose to help lessen the side effects until your body readjusts to the medicine.

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