How doxazosin works
Doxazosin binds selectively to so-called alpha-1 receptors. These are binding sites in the nervous system, in the salivary glands, and also on smooth muscle. When the active ingredient occupies the receptors, they are blocked for the messenger substances that would otherwise bind here – such as adrenaline and noradrenaline.
The active ingredient can also influence the smooth muscle in the wall of the blood vessels: When endogenous messenger substances such as norepinephrine bind to the alpha-1 receptors located here, the diameter of the blood vessels narrows – in other words, the arteries contract. This causes blood pressure to rise. If doxazosin blocks these receptors, the arteries dilate again, causing blood pressure to drop.
Absorption, breakdown and excretion
When is doxazosin used?
Doxazosin is used to treat high blood pressure and benign enlarged prostate (benign prostatic hyperplasia).
How doxazosin is used
The effect of doxazosin lasts for a long time, which is why it needs to be taken only once a day, regardless of meals.
What are the side effects of doxazosin?
Common side effects of doxazosin are urinary and respiratory tract infections. Drowsiness, headache, and impaired consciousness (somnolence) may also occur.
Occasionally, facial swelling (edema), skin rashes, impotence, or tinnitus may occur during treatment. Insomnia and depression are also possible.
Very rarely, complaints such as visual disturbances, spasms of the bronchial muscles (bronchospasms), jaundice (icterus) or a reduced number of white blood cells (leukopenia) are reported.
When should doxazosin not be taken?
Contraindications
Doxazosin should not be used in:
- known hypersensitivity to quinazolines (doxazosin, prazosin, terazosin)
- orthostatic hypotension (sudden drop in blood pressure on change of position)
- @ chronic urinary tract infections or bladder stones
Patients with impaired liver function or pathologically narrowed esophagus may use the active substance only under close medical supervision.
Interactions
- Antihypertensives (drugs for high blood pressure): Excessive blood pressure drop possible.
- PDE-5 inhibitors, i.e. potency-enhancing drugs such as sildenafil or tadalafil: uncontrolled drop in blood pressure possible.
Age restriction
Safety and efficacy of doxazosin in children and adolescents under 18 years of age have not been established.
Pregnancy and lactation
How to get medicines with doxazosin
Medicines with doxazosin require a prescription in Germany, Austria, and Switzerland and are only available from pharmacies with a doctor’s prescription.
