Doxazosin belongs to the general class of medicines called antihypertensives. It is used to treat high blood pressure (hypertension). High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure may also increase the risk of heart attacks.
These problems may be less likely to occur if blood pressure is controlled. Doxazosin works by relaxing blood vessels so that blood passes through them more easily. This helps to lower blood pressure. Doxazosin is also used to treat benign (noncancerous) enlargement of the prostate (benign prostatic hyperplasia [BPH]). Benign enlargement of the prostate is a problem that can occur in men as they get older.
The prostate gland is located below the bladder. As the prostate gland enlarges, certain muscles in the gland may become tight and get in the way of the tube that drains urine from the bladder. This can cause problems in urinating, such as a need to urinate often, a weak stream when urinating, or a feeling of not being able to empty the bladder completely.
Doxazosin helps relax the muscles in the prostate and the opening of the bladder. This may help increase the flow of urine and/or decrease the symptoms. However, doxazosin will not shrink the prostate. The prostate may continue to get larger. This may cause the symptoms to become worse over time. Therefore, even though doxazosin may lessen the problems caused by enlarged prostate now, surgery still may be needed in the future.
Doxazosin is available only with your doctor's prescription.
This product is available in the following dosage forms:
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make.
For this medicine, the following should be considered:
Allergies: Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Pediatric Population: Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of doxazosin in children with use in other age groups.
Geriatric Population: Dizziness, lightheadedness, or fainting may be especially likely to occur in elderly patients with high blood pressure, because these patients are usually more sensitive than younger adults to the effects of doxazosin.
Pregnancy: All Trimesters: Category C: Animal studies have shown an adverse effect and there are no adequate studies in pregnant women OR no animal studies have been conducted and there are no adequate studies in pregnant women.
Breastfeeding: There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Drug Interactions: Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur.
In these cases, your doctor may want to change the dose or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below.
The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Boceprevir
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases.
If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Asenapine
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you.
If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Other Interactions: Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems: The presence of other medical problems may affect the use of this medicine.
Make sure you tell your doctor if you have any other medical problems, especially:
Gastrointestinal (stomach and intestines) blockage—May increase the effect of doxazosin which could increase the chance of side effects.
Heart problems—May make condition worse.
Hypotension (decrease in blood pressure)—Possible increased the chance of fainting, especially after the first dose or a dose increase of this medicine.
Kidney disease—Possible increased sensitivity to the effects of doxazosin.
Liver disease—The effects of doxazosin may be increased, which may increase the chance of side effects.
Prostate cancer—Your doctor will want to make sure that you do not have prostate cancer before starting you on this medicine.
3 Proper Usage
For the regular tablet: To help you remember to take your medicine, try to get into the habit of taking it at the same time each day.
For the extended-release tablet:
Take in the morning with breakfast each day.
Swallow whole. Do not crush or chew.
Your doctor will not prescribe the extended-release tablet form of this medicine for high blood pressure. It can only be used in men for benign enlargement of the prostate.
For patients taking this medicine for high blood pressure :
In addition to the use of the medicine, your doctor has prescribed, treatment for your high blood pressure may include weight control and care in the types of foods you eat, especially foods high in sodium. Your doctor will tell you which of these are most important for you. You should check with your doctor before changing your diet.
Many patients who have high blood pressure will not notice any signs of the problem. In fact, many may feel normal. It is very important that you take your medicine exactly as directed and that you keep your appointments with your doctor even if you feel well.
Remember that doxazosin will not cure your high blood pressure but it does help control it. Therefore, you must continue to take it as directed if you expect to lower your blood pressure and keep it down. You may have to take high blood pressure medicine for the rest of your life .
If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease.
For patients taking this medicine for benign enlargement of the prostate:
Remember that doxazosin will not shrink the size of your prostate but it does help to relieve the symptoms of this condition. You may still need to have surgery later.
It may take up to 2 weeks before your symptoms improve.
Dosing: The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label.
The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
For oral dosage form (tablets):
For benign enlargement of the prostate: Adults—At first, 1 milligram (mg) once a day, in the morning or in the evening. Your doctor may increase your dose slowly up to 8 mg once a day.
For high blood pressure:
Adults—1 mg once a day to start. Your doctor may increase your dose slowly to as much as 16 mg once a day.
Children—Use and dose must be determined by your doctor.
For oral dosage form (extended-release tablets):
For benign enlargement of the prostate: Adults—At first, 4 milligram (mg) once a day, in the morning with breakfast. Your doctor may increase your dose slowly up to 8 mg once a day.
Missed Dose: If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Storage: Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children. Do not keep outdated medicine or medicine no longer needed.
4 Precautions to Take
It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly.
This is especially important for elderly patients, who may be more sensitive to the effects of this medicine.
For patients taking this medicine for high blood pressure: Do not take other medicines unless they have been discussed with your doctor.
This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.
Dizziness, lightheadedness, or sudden fainting may occur after you take this medicine, especially when you get up from a lying or sitting position.
These effects are more likely to occur when you take the first dose of this medicine. Taking the first dose at bedtime may prevent problems.
However, be especially careful if you need to get up during the night. These effects may also occur with any doses you take after the first dose.
Getting up slowly may help lessen this problem. If you feel dizzy, lie down so that you do not faint. Then sit for a few moments before standing to prevent the dizziness from returning.
The dizziness, lightheadedness, or sudden fainting is more likely to occur if you drink alcohol, stand for a long time, exercise, or if the weather is hot.
While you are taking this medicine, be careful to limit the amount of alcohol you drink. Also, use extra care during exercise or hot weather or if you must stand for a long time.
Doxazosin may cause some people to become drowsy or less alert than they are normal. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy, drowsy, or are not alert.
After you have taken several doses of this medicine, these effects should lessen.
The possibility of priapism, a painful or prolonged erection of the penis, is a rare side effect that can occur when taking doxazosin and must have immediate medical attention.
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine.
Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
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