Doxazosin: Uses, Dosage, Side Effects, Precautions and Interactions

It belongs to the family of drugs called antihypertensives, specifically alpha-1 receptor antagonists (alpha-blockers).


It is used to treat mild to moderate high blood pressure .

It can be used only with other medications that treat high blood pressure. It works to control blood pressure by relaxing blood vessels.

It is also used to treat the symptoms of benign prostatic hyperplasia (BPH or enlarged prostate ). It relaxes the muscles around the bladder neck, allowing urine to flow more freely. You may notice an improvement in symptoms within 1 to 2 weeks.

In what forms does this medicine come?

This medicine is available in 1 mg, 2 mg, and 4 mg tablets.


High blood pressure: The recommended adult dose of doxazosin ranges from 1 mg to 16 mg daily, depending on the individual’s needs and circumstances.

The recommended dose to start doxazosin, in this case, is 1 mg once a day. It can then be doubled every 1 to 2 weeks to a maximum of 16 mg once a day.


BPH: The recommended dose for enlarged prostate symptoms ranges from 1 mg to 8 mg once a day, depending on the individual’s needs and circumstances.

Doxazosin can be taken fasting or after eating without any problem.

Do not take this medicine if you are allergic to doxazosin, quinazolines, or any ingredient in the medication.

Side effects

  • Constipation.
  • Decreased frequency or amount of urine.
  • Dizziness.
  • Dry mouth.
  • Ejaculation problems.
  • General body pain.
  • Headache.
  • Indigestion.
  • Muscle cramps.
  • Nausea.
  • Nervousness, restlessness, unusual irritability.
  • Runny nose.
  • Drowsiness.
  • Perspiration.
  • Unusual tiredness or weakness
  • Abdominal pain.
  • Anxiety.
  • Depression.
  • Dizziness or lightheadedness (e.g., when getting up from a lying or sitting position).
  • Fainting (sudden).
  • Muscle spasms.
  • Difficulty breathing.
  • Swelling of the feet or lower legs.
  • Vision changes

Although most of the side effects listed above don’t happen very often, they could lead to severe problems if you don’t seek medical attention.

Stop taking medicine and seek immediate medical attention if any of the following occur:

  • Painful or prolonged erection of the penis (priapism). Although extremely rare, this condition requires immediate medical attention.
  • Chest pain.
  • Fast, pounding, or irregular heartbeat.
  • Symptoms of a severe allergic reaction (e.g., rash, hives, difficulty breathing, swelling of the mouth, tongue, face, or throat).

Some people may experience side effects other than those listed.

Are there other precautions?

Blood cell count: This drug can cause leukopenia (low white blood cell count), which may mean that your immune system is weak.

If you have a fever, talk to your doctor as soon as possible. Your doctor will also do blood tests regularly to check the blood cell count.

BPH: Doxazosin therapy does not cure or change the natural course of benign prostatic hyperplasia (BPH or enlarged prostate). It does not slow or stops the progression of BPH.

Keep in mind that BPH is not the same as prostate cancer, although it does cause many of the same symptoms. Men may have both BPH and prostate cancer at the same time.

Your doctor may check for prostate cancer before starting doxazosin and once a year after your 50th birthday (40 if you have a family member who has had prostate cancer).

Drowsiness / reduced alertness: Due to an excessive drop in blood pressure, people taking doxazosin should avoid driving or performing dangerous tasks for 24 hours after the first dose, increasing the amount, and when the drug is restarted. after not taking it for some time.

They should also avoid situations where the loss of consciousness could cause injury.

Liver and Kidney: If you have reduced liver function, take medications that slow liver metabolism or have reduced kidney function; talk to your doctor about how this medication may affect your medical condition.

Low blood pressure:  the first dose of doxazosin can cause a marked drop in blood pressure, especially when moving from a sitting or lying position to a standing position, and can even cause loss of consciousness.

A similar effect can occur if therapy is started again after stopping for more than a few doses. These effects are most likely to occur 2 to 6 hours after taking the drug.

Although the loss of consciousness due to an excessive drop in blood pressure is the most severe side effect of doxazosin, other symptoms of low blood pressure can occur, such as dizziness, lightheadedness, or loss of balance.

Lie down when symptoms of low blood pressure occur, and be careful when getting up from a lying position (move slowly). If you are bothered by dizziness, lightheadedness, or palpitations, tell your doctor so your dose can be considered.

The likelihood of an excessive drop in blood pressure can be reduced by limiting the starting dose of doxazosin to 1 mg, increasing the amount slowly, and starting any other blood pressure medication.

Long-term use: Long-term safety and efficacy (i.e., for more than four years) have not yet been established to benefit doxazosin in the treatment of BPH.

PDE-5 inhibitors: If you are taking a PDE-5 inhibitor (for example, sildenafil, tadalafil, or vardenafil) while taking this drug, you may be at risk for low blood pressure. Talk to your doctor.

Pregnancy: there are no studies on the effect of using this drug during pregnancy, but it is presumed that it should not be administered in this condition.

Lactation: It is unknown if this medicine is diluted into breast milk. Talk to your doctor to determine whether or not you can continue breastfeeding. In general, women should not breastfeed while taking this drug.

Children: not recommended for use by children.

Older people: Older people may experience an excessive drop in blood pressure or dizziness when taking doxazosin. Talk to your doctor if you have any concerns.


There can be an interaction between doxazosin and any of the following:

  • Other medicines lower blood pressure (e.g., thiazide diuretics, beta-blockers, other alpha-blockers).
  • PDE-5 inhibitors (for example, sildenafil, tadalafil, vardenafil).

If you take several medications, it does not mean that you should stop taking one of them. Talk to your doctor to find out how to handle the situation.

Medicines that were not mentioned can be combined with doxazosin.

Tell your doctor or prescriber about all prescription and non-prescription medications you are taking.

If you consume caffeine, alcohol, nicotine, or illegal drugs, tell your doctor as this can influence the effect of doxazosin and many other medications.