Meds and you

Updated 11 February 2013

Doxazosin

Doxazosin has a dilating effect on blood vessels and is often prescribed for the treatment of mild to moderately high blood pressure.

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Doxazosin is the active ingredient of Adco-Doxazosin, Cardugen and Cardura XL.

General information

Doxazosin has a dilating effect on blood vessels and is often prescribed for the treatment of mild to moderately high blood pressure.

This medication is not a cure for high blood pressure, but is effective in keeping it under control. For it to be effective, you must take it regularly - high blood pressure declines slowly and it may take a few weeks for Doxazosin to reach its full effect. Keep taking this medicine during this period, even if you are feeling better, or fail to notice any improvement.

Doxazosin is furthermore used to treat those patients with benign prostate hyperplasia, a non-malignant enlargement of the prostate that is common with ageing. The enlarged prostate gradually presses against the urethra, the tube that drains urine from the bladder, and often causes urinary difficulty. Doxazosin relaxes the prostate and bladder muscles and thereby increases urine flow.

The first couple of doses of this medication may cause a sudden drop in blood pressure, which may cause dizziness or blackouts when you suddenly get up. It is therefore advised that you should rest when starting treatment and that you should lie down for two hours afterwards. Until you know how you react to this medication, do not drive or attempt any activities that require alertness.

How does Doxazosin work?

Doxazosin relaxes the smooth muscle in the blood vessel walls, thereby causing vessels to dilate. This lowers blood pressure. It furthermore relaxes the muscles around the bladder exit and prostate gland and allows urine to flow out more easily.

Fast facts

Drug schedule: schedule 3

Available as: Doxazosin is available as tablets

What does it do? Doxazosin lowers blood pressure and makes urinating easier in those patients with an enlarged prostate

Overdose risk: medium

Dependence risk: low

Is Doxazosin available as a generic? yes

Is Doxazosin available on prescription only? yes

User information

Onset of effect: within 2 hours

Duration of action: up to 24 hours

Dietary advice: none

Stopping this medicine: use Doxazosin as prescribed by your doctor, and do not discontinue treatment before speaking to your doctor - suddenly stopping the drug may case your blood pressure to increase dangerously, or symptoms of benign prostate hyperplasia may return

Prolonged use: significant tolerance may develop with sustained long-term use

Special precautions

Consult your doctor before using this drug if:

  • you have liver or kidney disease
  • you have gastrointestinal or oesophageal obstruction
  • you are allergic to any medication
  • you are planning to have surgery
  • you are taking any other medication

Pregnancy: avoid. It is unknown how this medication may affect your baby. Consult your doctor before using this drug, or if you are planning to fall pregnant.

Breastfeeding: avoid. It is unknown how this medication may affect your baby. Consult your doctor before use.

Porphyria: avoid. It is unknown how this medication may affect your condition. Consult your doctor before use.

Infants and children: this medication is not intended for use in children.

The elderly: caution is advised in the elderly as side effects may be more common

Driving and hazardous work: this medication should be avoided as it may result in extreme sedation

Alcohol: avoid concomitant use of alcohol with this medication as adverse effects may be more common

Possible side effects

Side effect

Frequency

Consult your doctor

Common

Rare

Only if severe

In all cases

dizziness/ low blood pressure

x

x

vertigo

x

x

headache

x

x

diarrhoea

x

x

skin rash

x

x

fatigue

x

x

nausea

x

x

palpitations

x

x

abnormal vision

x

x

chest pain

x

x

jaundice

x

x

incontinence

x

x

priapism

x

x

Interactions

Drug interactions

digoxin

risk of digoxin toxicity

other medication for high blood pressure

increased blood-pressure-lowering effect

diuretics

increased blood-pressure-lowering effect

local anaesthetics

acute low blood pressure may occur

monoamine-oxidase inhibitors

increased blood-pressure-lowering effect

non-steroidal anti-inflammatory drugs

reduce Doxazosin's blood-pressure-lowering effect

Disease interactions

Consult your doctor before using this drug if you have liver disease, gastrointestinal or oesophageal obstruction, you are allergic to any medication, or if you are planning to have surgery.

Overdose action

A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention.

Recommended dosage

Adults: 4 - 8mg with a maximum dose of 16mg/day

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.

 

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