Doxazosin is in a group of drugs called alpha-adrenergic blockers. Doxazosin relaxes your veins and arteries so that blood can more easily pass through them. It also relaxes the muscles in the prostate and bladder neck, making it easier to urinate.
Doxazosin is used to treat hypertension (high blood pressure), or to improve urination in men with benign prostatic hyperplasia (enlarged prostate).
Doxazosin may also be used for other purposes not listed in this medication guide.
Important information
Doxazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using doxazosin. Do not stop using this medicine before surgery unless your surgeon tells you to.
You should not use this medication if you are allergic to doxazosin or similar medicines such as alfuzosin (Uroxatral), prazosin (Minipress), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin). Doxazosin may cause dizziness or fainting, especially when you first start taking it or when you start taking it again. Be careful if you drive or do anything that requires you to be alert. Avoid standing for long periods of time or becoming overheated during exercise and in hot weather. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.
If you stop taking doxazosin for any reason, call your doctor before you start taking it again. You may need a dose adjustment.
Tell your doctor about all other medications you use, especially other blood pressure medications including diuretics (water pills).
Before taking this medicine
You should not use this medication if you are allergic to doxazosin or similar medicines such as alfuzosin (Uroxatral), prazosin (Minipress), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin).
If you have liver disease or a history of prostate cancer, you may need a dose adjustment or special tests to safely take doxazosin.
Doxazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using this medication. Do not stop using doxazosin before surgery unless your surgeon tells you to.
FDA pregnancy category C. It is not known whether doxazosin will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication. It is not known whether doxazosin passes into breast milk or if it could harm a nursing baby. Do not use doxazosin without telling your doctor if you are breast-feeding a baby.
See also: Pregnancy and breastfeeding warnings (in more detail)
How should I take doxazosin?
Take doxazosin exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.
Your doctor may occasionally change your dose to make sure you get the best results.
Doxazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it, or when you start taking it again. Call your doctor if you have severe dizziness or feel like you might pass out.
You may feel very dizzy when you first wake up. Be careful when standing or sitting up from a lying position.
If you stop taking doxazosin for any reason, call your doctor before you start taking it again. You may need a dose adjustment.
Your blood pressure or prostate will need to be checked often. Visit your doctor regularly.
If you are being treated for high blood pressure, keep using this medication even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.
Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, heavy sweating, heart disease, dialysis, a low-salt diet, or taking diuretics (water pills). Tell your doctor if you have a prolonged illness that causes diarrhea or vomiting.
Store doxazosin at room temperature away from moisture and heat.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
If you miss your doses for several days in a row, contact your doctor before restarting the medication. You may need a lower dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include extreme dizziness or fainting.
What should I avoid?
Doxazosin may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
To prevent dizziness, avoid standing for long periods of time or becoming overheated during exercise and in hot weather.
Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.
Drinking alcohol can increase certain side effects of doxazosin.
Doxazosin side effects
Get emergency medical help if you have any of these signs of an allergic reaction to doxazosin: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have a serious side effect such as:
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feeling like you might pass out;
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fast or pounding heartbeats, fluttering in your chest;
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trouble breathing;
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swelling in your hands, ankles, or feet; or
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penis erection that is painful or lasts 4 hours or longer.
Less serious doxazosin side effects may include:
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
Doxazosin dosing information
Usual Adult Dose for Hypertension:
Initial dose: 1 mg orally once a day.
Maintenance dose: 1 to 16 mg orally once a day.
Usual Adult Doxazosin Dose for Benign Prostatic Hyperplasia:
Initial dose:
Immediate-release: 1 mg orally once a day.
Extended-release: 4 mg orally once a day with breakfast
Maintenance dose:
Immediate-release: 1 to 8 mg orally once a day.
Extended-release: 4 to 8 mg orally once a day with breakfast. Depending on the patient"s symptomatic response and tolerability, the dose may be increased to 8 mg (the maximum recommended dose). The recommended titration interval is 3 to 4 weeks.
If switching from immediate-release doxazosin to extended-release tablets, therapy should be initiated with the lowest dose (4 mg once daily). Prior to starting therapy with doxazosin extended-release tablets, the final evening dose of immediate-release doxazosin should not be taken. If doxazosin extended-release is discontinued for several days, therapy should be restarted using the 4 mg once daily dose.
Usual Geriatric Dose for Hypertension:
Initial dose: 0.5 mg orally once a day.
What other drugs will affect doxazosin?
Tell your doctor about all other medications you use, especially:
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sildenafil (Viagra, Revatio)
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tadalafil (Cialis);
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vardenafil (Levitra); or
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other blood pressure medications, including diuretics (water pills).
This list is not complete and other drugs may interact with doxazosin. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.
