Doxazosin (Cardura, Cardura XL) is used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia or BPH), which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency. Doxazosin (Cardura) is also used alone or in combination with other medications to treat high blood pressure. Doxazosin is in a class of medications called alpha-blockers. It relieves the symptoms of BPH by relaxing the muscles of the bladder and prostate. It lowers blood pressure by relaxing the blood vessels so that blood can flow more easily through the body.
Doxazosin comes as a tablet and an extended-release tablet to take by mouth. The doxazosin tablet is usually taken with or without food once a day in the morning or in the evening. The doxazosin extended-release tablet is usually taken once a day with breakfast. To help you remember to take doxazosin, take it around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take doxazosin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Swallow the extended-release tablets whole; do not split, chew, or crush them.
Your doctor will start you on a low dose of doxazosin and gradually increase your dose, not more than once every 1 to 2 weeks. If you stop taking doxazosin for a few days or longer, call your doctor. Your doctor will have to start you again on the lowest dose of doxazosin and gradually increase your dose.
Doxazosin controls high blood pressure and the symptoms of BPH but does not cure them. It may take a few weeks before you feel the full benefit of doxazosin. Continue to take doxazosin even if you feel well. Do not stop taking doxazosin without talking to your doctor.
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
Before taking doxazosin,
- tell your doctor and pharmacist if you are allergic to doxazosin, prazosin (Minipress), terazosin (Hytrin), or any other medications.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: antihistamines; clarithromycin (Biaxin, in Prevpac); ipratropium (Atrovent); itraconazole (Sporanox); ketoconazole (Nizoral); medications for erectile dysfunction (ED) such as sildenafil (Viagra), tadalafil (Cialis), or vardenafil (Levitra); medications for high blood pressure; medications for HIV/AIDS including atazanavir (Reyataz), indinavir (Crixivan), nelfinavir (Viracept), ritonavir (Norvir, in Kaletra), or saquinavir (Fortovase, Invirase); medications for irritable bowel disease, motion sickness, Parkinson's disease, ulcers, or urinary problems; nefazodone; telithromycin (Ketek); and voriconazole (Vfend). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- tell your doctor if you have angina (chest pain); low blood pressure; or if you have or have ever had prostate cancer or liver disease. If you are taking the extended-release tablet, tell you doctor if you have constipation, short bowel syndrome (a condition where more than half of the small intestine has been removed by surgery or damaged by disease), or narrowing or a blockage of the intestines.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking doxazosin, call your doctor.
- talk to your doctor about the risks and benefits of taking doxazosin if you are 65 years of age or older. Older adults should not usually take doxazosin because it is not as safe as other medications that can be used to treat the same conditions.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking doxazosin. If you need to have eye surgery at any time during or after your treatment, be sure to tell your doctor that you are taking or have taken doxazosin.
- you should know that doxazosin may make you drowsy or dizzy. Do not drive a car, operate machinery, or perform dangerous tasks for 24 hours after the first time you take doxazosin or after your dose is increased.
- you should know that doxazosin may cause dizziness, lightheadedness, and fainting when you get up too quickly from a lying position. This is more common when you first start taking doxazosin, when your dose is increased, or if your treatment has been stopped for more than a few days. To avoid this problem, get out of bed slowly, resting your feet on the floor for a few minutes before standing up. If you experience these symptoms, sit or lie down. If these symptoms do not improve, call your doctor.
Follow your doctor's directions for your meals, including advice for a reduced salt (sodium) diet.
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one. Check with your doctor if you have missed two or more doses.
Doxazosin may cause side effects. Tell your doctor if any of these symptoms or those listed in the SPECIAL PRECAUTIONS section are severe or do not go away:
- swelling of the hands, feet, ankles, or lower legs
- shortness of breath
- weight gain
- muscle or joint pain or weakness
- abnormal vision
- runny nose
- decreased sexual ability
Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:
- rapid, pounding, or irregular heartbeat
- chest pain
- shortness of breath
- painful erection of the penis that lasts for hours
Doxazosin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
Symptoms of overdose may include:
If you are taking doxazosin extended-release tablets, you may notice something that looks like a tablet in your stool. This is just the empty tablet shell, and this does not mean that you did not get your complete dose of medication.
Keep all appointments with your doctor. If you are taking doxazosin to control high blood pressure, your blood pressure should be checked regularly to determine your response to doxazosin.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Last Reviewed: September 1, 2010.