Doxazosin - Use | Dose | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Doxazosin is a drug from the group of alpha blockers, and is used for lowering blood pressure as well as for the alleviation of the symptoms of benign prostate enlargement. Some studies suggest that this drug lowers the level of LDL cholesterol and increases levels of HDL cholesterol.1 It lowers blood pressure by reducing resistance in peripheral blood vessels.2


Doxazosin should not be used in the following conditions:

  • In patients younger than 12 years
  • In patients allergic to this medicine
  • In patients who have low blood pressure
  • In patients who have liver or kidney damage
  • In patients who have heart problems
  • In patients who have intestinal blockage

Doxazosin, pregnancy and breastfeeding

Doxazosin belongs to the group C, because studies performed in rabbits have shown that this medication may be harmful to the fetus if taken in larger doses. However, sometimes the benefits of its application to the mother outweighs the risk to the child as is the case of pheochromocytoma (tumor of the adrenal gland, which is characterized by high blood pressure). Doxazosin is proved to be a safe drug for the treatment of pheochromocytoma in pregnant women.3

It is not known whether Doxazosin is excreted in breast milk, so you should be cautious when using this drug during breastfeeding.


The usual initial dose is 1 mg per day. The initial dose should be lower, because the use of higher doses usually leads to the orthostatic hypotension (a sudden drop in blood pressure when getting up from a sitting or lying position). After several weeks, the dose may be increased up to 2 mg or 4 mg daily. The maximum daily dose is 16 mg and it should be used only to treat extremely high blood pressure.

Do not discontinue taking this medicine on your own, because it can lead to the worsening of symptoms.

Doxazosin is taken regardless of the food.


Doxazosin should not be used in combination with the following medications:

  • Drugs used to treat erectile dysfunction, a so-called PDE-5 inhibitors, such as:
    • sildenafil (Viagra)
    • tadalafil
    • vardenafil and others.
  • Tizanidine (a muscle relaxant). Concurrent use of these two drugs can lead to a significant reduction in blood pressure.
  • Boceprevir (a drug used to treat hepatitis C). Boceprevir can increase the concentration of Doxazosin in the blood, which increases the risk of side effects.
  • Grastek (timothy grass pollen allergen extract) that is used to relieve allergy symptoms. Grastek can sometimes cause anaphylactic shock, which is treated with adrenalin. Doxazosin may reduce the effect of adrenaline and thus reduce its effectiveness in the treatment of anaphylactic shock.
  • Sodium oxybate (a drug used to treat cataplexy). Co-administration of these two drugs increases the risk of adverse effects on the central nervous system.

Side effects

Doxazosin may cause the following side effects:

  • Increase in body weight
  • Loss of appetite
  • Heat flush attacks
  • Shortness of breath, coughing or wheezing
  • Abnormal noise or buzzing in the ears
  • Urinary incontinence
  • Drowsiness
  • Headache
  • Low blood pressure
  • Damage to the liver accompanied by jaundice
  • Mood swings (anxiety and depression)
  • Rhinitis
  • Dry mouth
  • Swelling of the feet


  1. NCBI link 1
  2. NCBI link 2
  3. NCBI link 3

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