What is it and how does it work?
Alpha blockers inhibit the effect of norepinephrine, a hormone that causes constriction of blood vessels. By relaxing the muscles in the walls of the blood vessels, arteries dilate and blood pressure decreases.

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A few Alpha Blockers

• Prazosin in Minipress.
• Terazosin in Hytrin.
• Doxazosin in Cardura.

Who benefits from Alpha Blockers?
Alpha blockers may improve urinary flow in men with partial obstruction due to an enlarged prostate.

It seems that alpha blockers slightly increases HDL-cholesterol, and may lower total cholesterol and triglycerides. This may be an advantage to patients with blood fat abnormalities.

Alpha blockers may be of benefit in some patients with glucose intolerance.

Indications:

• Patients with prostatic hypertrophy – enlarged prostrate.
• Possibly in patients with dyslipidaemia – abnormal blood fats.
• Possibly in some patients with glucose intolerance.

How to take Alpha Blockers
These drugs may cause a sharp drop in blood pressure, especially the first dose. This could lead to dizziness or fainting on standing. To minimise this effect it is best to start with a small dose, or to take the drug in bed at night. Use with caution in patients prone to fainting.

Who should not take Alpha Blockers?

• Patients with postural hypotension – when blood pressure falls on standing, causing dizziness or fainting.
• Patients with urinary incontinence.
• Safety in pregnancy not established.

Possible side effects

• Orthostatic hypotension where blood pressure falls on standing. This problem seems to be worse in elderly patients.
• Headaches, dry mouth and nasal congestion.
• Rarely, it causes urinary incontinence in women.

Possible drug interactions?
Alcohol may increase the adverse effects of these drugs.

Written by Dr Kathleen Coetzee, MBChB.

Read more:
Am I at risk for hypertension?
Medical zone

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