Alpha blockers are also called alpha-adrenergic antagonists. They treat a variety of conditions like high blood pressure, benign prostatic hyperplasia (BPH) and Raynaud's disease. These drugs relax the muscles and help small blood vessels to remain open. They work by preventing the hormone norepinephrine (noradrenaline) from contracting the muscles in the walls of smaller arteries and veins. Blocking that effect causes the vessels to remain open and relaxed. This improves blood flow and lower BP.
What are alpha blockers?
Alpha blockers are also called alpha-adrenergic antagonists. They treat a variety of conditions like high blood pressure, benign prostatic hyperplasia (BPH) and Raynaud's disease.
There are various alpha blockers in long and short term acting forms. Examples of alpha blockers are:
Classification: they are classified into two categories
Some α1-adrenergic blockers are:
Some α2-adrenergic blockers are:
How do they work?
Alpha-blockers are the drugs that work by blocking the transmission of nerve impulses. Some nerve endings release a chemical (neurotransmitter) called nor-adrenaline when the nerve or neuron is stimulated. This chemical then stimulates alpha-adrenergic receptors. They are the tiny structures which occur on cells in various parts of the body including the heart, smooth muscle, and blood vessels. When the receptors are stimulated, they cause various effects. The alpha-blocker medicine attaches to alpha-adrenergic receptors and stops the receptor from stimulating.
For what conditions are these drugs prescribed?
They are prescribed primarily for two conditions:
These are prescribed by the doctors who are highly qualified and specialized for treating hypertension. These are prescribed only if the other drugs are not working properly in the treatment of the hypertension. The drugs are:
Angiotensin-converting enzyme (ace) inhibitors
Diuretics (water tablets)
Prostate gland enlargement:
The decision to use this drug in treatment usually depends upon the fact that if the symptoms are very much annoying or not. Alpha-blockers work by relaxing the muscles around the bladder and prostate so that passing urine becomes easy.
What are the important drug interactions?
There are a number of drugs that must be completely avoided while taking alpha blockers:
Phosphodiesterase-5 inhibitors. For example- Sildenafil
Antidepressants such as tricyclic antidepressants.For example- Amitriptyline, Mirtazapine, or Venlafaxine.
When these medicines are combined with an alpha-blocker, you may counter postural hypotension i.e. a sudden drop in blood pressure.
What are the expected side effects?
The most common side-effects are slight drowsiness, headaches and dizziness; these are most likely to occur in the first two weeks of the treatment.
Who cannot take this drug?
People who have had postural hypotension and micturition syncope (fainting while urinating) are advised to avoid this drug or they must consult their doctor in case they find the need to take the drug.