Generic Name: doxazosin, Oral tablet

Generic Name:

doxazosin, Oral tablet

Cardura

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SECTION 1 of 5

Highlights for doxazosin

Oral tablet
1

Doxazosin is used to treat benign prostatic hyperplasia (BPH) and high blood pressure.

2

Common side effects include dizziness, tiredness, and swelling of your feet, hands, arms, and legs.

3

Doxazosin can cause your blood pressure to become low, which may cause dizziness, lightheadedness, and vertigo when standing. This is most common with your first dose.

4

Rarely, doxazosin causes priapism, which is a painful erection that will last for hours. This condition can lead to permanent loss of sexual function if it isn’t treated.

IMPORTANT INFORMATION

Low blood pressure warning

Doxazosin can cause your blood pressure to become low. This may cause dizziness, lightheadedness, and vertigo when you stand up. This is most common with your first dose of medication. The reaction is known as a “first-dose” effect, but it can also occur when your doctor changes your dose. Your doctor will start you on the lowest dose and slowly increase it.

Cataract surgery

Intraoperative floppy iris syndrome (IFIS) can occur during cataract surgery in people who take or have taken doxazosin.

You may not have to stop taking doxazosin prior to your surgery, but you should tell your doctor if you have a cataract surgery planned.

Drug Features

Doxazosin is a prescription medication. It’s available as an oral tablet and an oral extended-release tablet.

It’s also available in a generic version. Generic drugs usually cost less. In some cases they may not be available in every strength or form as the brand. Talk to your healthcare provider to see if the generic will work for you.

This drug may be used as part of a combination therapy. That means you may need to take it with other drugs.

Why It's Used

Doxazosin is used to treat benign prostatic hyperplasia (BPH) and high blood pressure (immediate-release tablets only).

More Details

How It Works

Doxazosin belongs to a class of drugs called alpha-1-adrenergic blockers. It works by blocking certain chemicals, which helps to widen blood vessels and relax muscles in your prostate and in your bladder.

Why It's Used

Doxazosin is used to treat benign prostatic hyperplasia (BPH) and high blood pressure (immediate-release tablets only).

The most up-to-date guidelines for the treatment of high blood pressure don’t recommend the use of doxazosin.

SECTION 2 of 5

doxazosin Side Effects

Oral tablet

Most Common Side Effects

  • The most common side effects that occur with doxazosin when treating benign prostatic hyperplasia (BPH) include:

    • low blood pressure
    • dizziness
    • shortness of breath
    • tiredness
    • abdominal pain
    • diarrhea
    • headache
    • swelling of your feet, hands, arms, and legs
  • The most common side effects that occur when treating high blood pressure include:

    • low blood pressure
    • dizziness
    • headache
    • tiredness
    • nausea
    • runny nose
    • swelling of your feet, hands, arms, and legs

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening, or if you think you’re experiencing a medical emergency, call 9-1-1.

  • heart problems. Symptoms may include:

    • rapid, pounding, or irregular heartbeat
    • chest pain
  • painful erection that lasts for hours (priapism)

  • severe allergic reaction. Symptoms may include:

    • wheezing
    • chest tightness
    • itching
    • swelling of your face, lips, tongue, or throat
    • hives
  • breathing problems. Symptoms may include:

    • shortness of breath
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Mild side effects may disappear within a few days or a couple of weeks. Talk to your doctor or pharmacist if they’re more severe or don’t go away.

Doxazosin is sedating and causes drowsiness. Be careful driving and doing other activities that require you to be alert until you know how it affects you.

Doxazosin may cause your blood pressure to become low. This may cause dizziness, lightheadedness, and vertigo when you stand up. This is most common with your first dose of medication and is known as a “first-dose” effect. But it can also happen when your doctor changes your dose. Your doctor will start you on the lowest dose of doxazosin and slowly increase it.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 5

doxazosin May Interact with Other Medications

Oral tablet

Doxazosin can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Medications That Might Interact with This Drug

Drugs that inhibit CYP3A4 enzymes

Doxazosin is broken down by the CYP3A4 enzyme—a common enzyme that processes drugs. Medications that block it from working or over work it to increase its effects, will change the level of doxazosin in your body. It’s important to let your doctor know all the medications you’re taking so they can monitor the effect of doxazosin when taken with these medications.

Examples are:

  • CYP3A4 Inhibitors
    • Antifungals (Azole antifungals): Fluconazole, ketoconazole, voriconazole
    • HIV medications (protease inhibitors): ritonavir, saquinavir, indinavir
    • Macrolide antibiotics: clarithromycin, telithromycin, erythromycin
    • Grapefruit juice
  • CYP3A4 Inducers
    • Antiseizure: fosphenytoin, phenytoin, carbamazepine
    • HIV medications (non-nucleoside reverse transcriptase inhibitors): efavirenz, etravirine
    • St. John’s wort

Blood pressure medications
  • drugs to lower your blood pressure. Combining doxazosin with any drug that lowers your blood pressure can increase your risk for lowering your blood pressure too much.
    Examples are:
    • aldosterone antagonists, such as: spironolactone, eplerenone
    • angiotensin-converting enzyme inhibitors (ACEIs), such as: benazepril, lisinopril, enalapril, fosinopril
    • angiotensin receptor blockers (ARBs), such as: losartan, candesartan, valsartan
    • beta-blockers, such as: atentolol, bisoprolol, metoprolol, propranolol
    • calcium channel blockers (DHP), such as: amlodipine, nifedipine, nicardapine,
    • calcium channel blockers (non DHP) such as: diltiazem, verapamil
    • centrally-acting adrenergic agents, such as: clonidine, guanfacine, methyldopa
    • direct renin inhibitors, such as: aliskiren
    • diuretics (loop and thiazide/thiazide-like): amiloride, chlorthalidone, furosemide, metolazone
    • vasodilators: hydralazine, minoxidil
    • nitrates, such as: isosorbide mononitrate, isosorbide dinitrate, nitroglycerin transdermal patch
  • drugs that increase your blood pressure. Combining doxazosin with drugs that increase your blood pressure can cancel the effects of both medications. Examples are:
    • symphathomimetics (decongestants): pseudoephedrine, oxymetazoline, phenylephrine
    • erythropoiesis-stimulating agents (red blood cell production stimulators): darbepoetin alfa, epoetin alfa
    • contraceptives (birth control): ethinyl estradiol, ethinyl estradiol/levonorgestrel
  • drugs to treat pulmonary arterial hypertension. Combining doxazosin with these drugs can increase your risk of low blood pressure.
    Examples are:
    • endothelin receptor blockers, such as: ambrisentan, bosentan, macitenan
    • phosphodiaesterase-5 (PDE-5) blockers, such as: sildenafil, tadalafil
    • nitric oxide

Erectile dysfunction drugs
  • phosphodiaesterase-5 (PDE-5) inhibitors. Combining doxazosin with PDE-5 inhibitors can increase the blood pressure-lowering effects of doxazosin and increase your risk of side effects.
    An example is:
    • tadalafil. Combining these drugs can cause a serious drop in your blood pressure.

Attention deficit hyperactivity disorder (ADHD) drug
  • methylphenidate

Combining this drug with doxazosin can lower the effect of doxazosin. This may cause your blood pressure to stay too high.

Parkinson’s disease drugs

Combining these drugs with doxazosin can increase your risk of low blood pressure when standing:

  • levodopa
  • MAO inhibitors (MAOIs).
    Examples are:
    • isocarboxazid (Marplan)
    • phenelzine (Nardil)
    • tranylcypromine (Parnate)
    • selegiline (Emsam, Eldepryl, Zelapar)

Cancer drugs

Combining these medications with doxazosin increases your risk of low blood pressure.

  • amifostine. Your doctor may stop your doxazosin 24 hours before giving you amifostine. If you can’t stop taking doxazosin, you shouldn’t take amifostine.
  • obinutuzumab. Your doctor may stop your doxazosin 12 hours before giving you obinutuzumab. You shouldn’t take doxazosin for 1 hour after taking obinutuzumab.
  • rituximab

Hepatitis C drug
  • boceprevir

Combining boceprevir with doxazosin will increase the levels of doxazosin and increase your risk of side effects. Don’t take these medications together.

Herbal medications
  • yohimbine. Combining this with doxazosin can lower the effect of doxazosin and cause your blood pressure to stay too high.
  • Herbs that can increase your blood pressure. Combining these with doxazosin can lower the effect of doxazosin and cause your blood pressure to stay too high.
  • Herbs that can lower your blood pressure. Combining these with doxazosin can increase your risk of low blood pressure.

Antidepressant
  • duloxetine

Combining this with doxazosin can increase your risk of low blood pressure when standing up.

Seizure drugs
  • barbiturates, such as:
    • Phenobarbital
    • Pentobarbital
    • Primidone

Combining these with doxazosin can increase your risk of low blood pressure.

Intermittent claudication drug
  • pentoxifylline

Combining this with doxazosin can increase your risk of low blood pressure.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

People with liver problems

Doxazosin is broken down by your liver. If you have liver problems, you may have an increased risk of side effects.

People having cataract surgery

Intraoperative floppy iris syndrome (IFIS) can occur during cataract surgery in people who take or have taken doxazosin.

You may not have to stop taking doxazosin prior to your surgery, but you should tell your doctor if you have a cataract surgery planned.

Pregnant women

Doxazosin is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Tell your doctor if you’re pregnant or plan to become pregnant. Doxazosin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Women who are nursing

Doxazosin passes through breast milk.

You and your doctor may need to decide whether you’ll take this medication or breastfeed.

For Seniors

This medication shouldn’t be used to treat high blood pressure in people aged 65 years and older. If you’re 65 or older, you’re at increased risk of having low blood pressure when you stand up. This can lead to dizziness and lightheadedness.

For Children

The safety and effectiveness of doxazosin haven’t been established in people younger than 18 years old for treating benign prostatic hyperplasia (BPH).

Allergies

Doxazosin can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.

SECTION 4 of 5

How to Take doxazosin (Dosage)

Oral tablet

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What Are You Taking This Medication For?

Benign prostatic hyperplasia (BPH)
Form: Oral immediate-release tablet
Strength: 1 mg, 2 mg, 4 mg, and 8 mg
Form: Oral extended-release tablet
Strength: 4 mg and 8 mg
Adult Dosage (ages 18–64 years)

Extended-release tablet:

  • The starting dose is 4 mg per day with breakfast.
  • Your doctor may increase your dose to a maximum of 8 mg per day in 3 to 4 weeks after starting the medication.
  • When switching from immediate-release tablets to extended-release tablets: You may be started on 4 mg per day. Before you start taking the extended-release tablet, don’t take your last evening dose of the immediate-release tablet.

Immediate-release tablet:

  • The starting dose is 1 mg per day in the morning or evening.
  • Your doctor may increase your dose by 2 mg every 1–2 weeks, up to a maximum of 8 mg per day.
Child Dosage (ages 0–17 years)

A safe and effective dose hasn’t been established for this age group.

Senior Dosage (ages 65 years and older)

Your body may process this drug more slowly. Your doctor may start you on a lowered dose so that too much of this drug doesn’t build up in your body. Too much of the drug in your body can be toxic.

High blood pressure
Form: Oral immediate-release tablet
Strength: 1 mg, 2 mg, 4 mg, and 8 mg
Adult Dosage (ages 18–64 years)
  • The starting dose is 1 mg per day.
  • Based on your blood pressure, your doctor may increase your dose 2 mg at a time to a maximum dose of 16 mg per day.
Child Dosage (ages 0–17 years)

A safe and effective dose hasn’t been established for this age group.

Senior Dosage (ages 65 years and older)

Your body may process this drug more slowly. Your doctor may start you on a lowered dose so that too much of this drug doesn’t build up in your body. Too much of the drug in your body can be toxic.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Doxazosin comes with risks if you don't take it as prescribed.

If You Don't Take It At All

Your symptoms may not improve or they may get worse over time.

If You Stop Taking It Suddenly

If your condition improved while taking the medication regularly and you stop taking doxazosin suddenly, your symptoms may come back.

If You Don't Take It on Schedule

You may not see a full benefit of this medication. If you double up your dose or take it too close to your next scheduled time, you may be at higher risk of experiencing serious side effects.

What to Do If You Miss a Dose

If you miss a dose, take it as soon as you can. However, if it’s just a few hours until your next dose, wait and take a single dose.

Never try to catch up by taking two doses at once. This could result in toxic side effects

How to Tell If the Drug Is Working

You may be able to tell this drug is working for benign prostatic hyperplasia (BPH) if you have an easier time urinating and experience fewer symptoms of obstruction and irritation.

You may be able to tell it’s working for high blood pressure if your blood pressure is lower. High blood pressure doesn’t often have symptoms, so you may need to take a blood pressure test to know if your pressure is lower.

Doxazosin is a long-term drug treatment.

Important Considerations for Taking Doxazosin
should take with food icon Take the extended-release tablet with breakfast
timing icon Take the extended-release tablet in the morning
not crush icon Don’t cut or crush the extended-release form See Details
storage icon Store in temperatures from 59–86°F (15–30°C) See Details
Prescription refillable icon Prescription is refillable
travel icon Travel See Details
Self-Management icon Self-Management See Details
Not Usually Stocked Not every pharmacy stocks this drug, so call ahead
Clinical Monitoring icon Clinical Monitoring See Details
Prior authorization Insurance See Details

Don’t cut or crush the extended-release form

Swallow the extended-release tablet whole.

You can cut or crush the immediate-release tablet

Store in temperatures from 59–86°F (15–30°C)

Keep drugs away from areas where they could get wet, such as bathrooms. Store them away from moisture and damp locations.

Travel

When traveling with your medication:

  • Always carry it with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s preprinted label to identify the medication. Keep the original prescription-labeled box with you when traveling.

Self-Management

If you’re taking this drug for high blood pressure, your doctor may recommend getting a blood pressure monitor. You may keep it at home to check your blood pressure on a regular basis in between clinic visits.

Clinical Monitoring

If you’re taking this drug for high blood pressure, your doctor will check your blood pressure at every visit to make sure the medication is working correctly. Your doctor may increase your dose if your blood pressure is too high or lower your dose if your blood pressure is too low.

Insurance

Many insurance companies will require a prior authorization before they approve the prescription and pay for doxazosin.

Are There Any Alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives

What does the pill look like?

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SECTION 5 of 5

How Much Does doxazosin Cost?

Oral tablet
We've partnered with GoodRX so you can compare prices and save money on your next prescription. Check out the lowest cash prices below and enter your zip code to find the best deal near you.

Compare prices and save money on your next refill!

Lowest price for doxazosin

Rite-Aid $9.99
CVS Pharmacy $11.99
Kroger Pharmacy $13.24
These represent the lowest cash prices for doxazosin and may be lower than your insurance.

Find the lowest prices of doxazosin near you

These represent the lowest cash prices for doxazosin and may be lower than your insurance.

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Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on June 25, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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