- Alpha-1 blocker
Alpha-1 blockers (also called alpha-adrenergic blocking agents) constitute a variety of drugs which block α1-adrenergic receptors in
arteries andsmooth muscle s.Indications
Examples of alpha blockers
Non-selective Adrenergic blockers:
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Phenoxybenzamine
*Phentolamine (Regitine)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 thebaroreflex response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known asorthostatic hypotension or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. Additionally, the risk offirst 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 forhypotension , such as otherantihypertensive s andvasodilator s.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.References
External links
* [http://www.drugdigest.org/DD/Comparison/NewComparison/0,10621,5-17,00.html DrugDigest] - Alpha blockers
* [http://www.rxlist.com/cgi/generic2/tamsul_cp.htm RxList.com] - Tamsulosin
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