Doxazosin is used alone or with other drugs to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This medication works by relaxing blood vessels so blood can flow more easily.
Doxazosin is also used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia-BPH). It does not shrink the prostate, but it works by relaxing the muscles in the prostate and part of the bladder. This helps to relieve symptoms of BPH such as difficulty in beginning the flow of urine, weak stream, and the need to urinate frequently or urgently (including during the middle of the night).
Doxazosin belongs to a class of drugs known as alpha blockers.
OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.
Read the Patient Information Leaflet if available from your pharmacist before you start taking doxazosin and each time you get a refill. If you have any questions, ask your doctor or pharmacist.
Take this medication by mouth with or without food as directed by your doctor, usually once daily.
Doxazosin may cause a sudden drop in your blood pressure, which could lead to dizziness or fainting, usually within 2 to 6 hours after you take it. This risk is higher when you first start taking this drug, after your doctor increases your dose, or if you restart treatment after you stop taking it. During these times, avoid situations where you may be injured if you faint.
To avoid injury related to dizziness or fainting, take your first dose of doxazosin at bedtime unless otherwise directed by your doctor. Your doctor will start this medication at a low dose and gradually increase your dose. Any time your dose is increased or if you restart treatment after you have stopped it, take your first dose at bedtime unless otherwise directed. Follow your doctor's instructions carefully.
The dosage is based on your medical condition and response to treatment.
Take this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. If you miss taking doxazosin for a few days, you may need to restart treatment at the low dose and gradually increase your dose again. Consult your doctor for more details.
It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick.
You should see a benefit from this drug within 1 to 2 weeks. Tell your doctor if your condition does not improve or if it worsens (for example, your blood pressure readings remain high or increase, or your BPH symptoms worsen).
Dizziness, lightheadedness, drowsiness, unusual tiredness, or weight gain may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: fainting, shortness of breath, weakness, swelling of hands/feet, yellowing eyes/skin, dark urine, easy bleeding/bruising, fever, persistent sore throat.
Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Before taking doxazosin, tell your doctor or pharmacist if you are allergic to it; or to other alpha blockers such as prazosin or terazosin; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: heart disease (such as congestive heart failure, angina, heart attack in last 6 months), liver disease, certain eye problems (cataracts, glaucoma).
This drug may make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages. See also How to Use section.
Before having surgery (including cataract/glaucoma eye surgery), tell your doctor or dentist if you are taking or have ever taken this medication, and about all the other products you use (including prescription drugs, nonprescription drugs, and herbal products).
Older adults may be more sensitive to the side effects of this drug, especially dizziness and low blood pressure when getting up from a sitting or lying position. These side effects can increase the risk of falling.
During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.
It is unknown if this drug passes into breast milk. Consult your doctor before breast-feeding.
Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.
Some products that may interact with this drug include: other alpha blocker drugs (such as prazosin, tamsulosin).
If you are also taking a drug to treat erectile dysfunction-ED or pulmonary hypertension (such as sildenafil, tadalafil), your blood pressure may get too low which can lead to dizziness or fainting. Your doctor may need to adjust your medications to minimize this risk.
Other medications can affect the removal of doxazosin from your body, which may affect how doxazosin works. Examples include azole antifungals (such as itraconazole, ketoconazole), boceprevir, macrolide antibiotics (such as clarithromycin), HIV protease inhibitors (such as lopinavir, ritonavir), among others.
Check the labels on all your medicines (such as cough-and-cold products, diet aids, or NSAIDs such as ibuprofen, naproxen) because they may contain ingredients that could increase your blood pressure. Ask your pharmacist for more details.
If overdose is suspected, contact a poison control center or emergency room right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness, fainting, weakness.
Do not share this medication with others.
If you have high blood pressure, lifestyle changes that may help this medication work better include exercising, stopping smoking, and eating a low-cholesterol/low-fat diet. Consult your doctor for more details.
Have your blood pressure checked regularly while taking this medication. Learn how to monitor your own blood pressure at home, and share the results with your doctor.
Laboratory and/or medical tests (such as prostate exams, blood pressure) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.
If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up. See also How to Use section.
Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.
Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.
Information last revised December 2014. Copyright(c) 2014 First Databank, Inc.
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