(also called alpha-adrenergic blocking agents) constitute a variety of drugs which block α1-adrenergic receptors
and smooth muscles
These drugs may be used to treat:
Examples of alpha blockers
Selective Alpha-1 blockers include:
Non-selective Adrenergic blockers:
Tamsulosin is relatively selective for α1a-adrenergic receptors, which are mainly present in the prostate. Hence, it may have a more selective action in BPH with minimal effects on blood pressure.
Adverse effects and interactions
By reducing α1
-adrenergic activity of the blood vessels, these drugs may cause hypotension
(low blood pressure) and interrupt the baroreflex
response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known as orthostatic hypotension
or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. Additionally, the risk of first dose phenomenon
may be reduced by starting at a low dose and titrating
upwards as needed.
Because these medications may cause orthostatic hypotension, as well as hypotension in general, these agents may interact with other medications that increase risk for hypotension, such as other antihypertensives and vasodilators.
As discussed above, tamsulosin may have less risk for hypotension and orthostatic hypotension due to its selectivity for α1a-adrenergic receptors. On the other hand, the drug (a) elevates risk for floppy iris syndrome, and (b) might show ADRs characteristic of the sulfa related drugs.