This MedLibrary.org supplementary page on Alpha blocker is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
Alpha blockers (also called alpha-adrenergic blocking agents) constitute a variety of drugs which block α1-adrenergic receptors in arteries and smooth muscles.
Contents |
Indications
These drugs may be used to treat:
- benign prostatic hyperplasia (BPH)
- Lower urinary tract symptoms
- Post Transurethral microwave thermotherapy (TUMT) and Transurethral needle ablation of the prostate (TUNA) procedures
- high blood pressure (hypertension). This is not typically the drug of choice unless the patient also has BPH.
- symptoms of non inflammatory chronic pelvic pain syndrome, a type of prostatitis. As a side effect they may reduce blood pressure and result in lightheadedness.
Examples of alpha blockers
Alpha blockers include:
- Doxazosin (Cardura)
- Prazosin (Minipress)
- Phenoxybenzamine
- Phentolamine (Regitine)
- Tamsulosin (Flomaxtra/Flomax)
- Alfuzosin (Uroxatral)
- Terazosin (Hytrin)
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.
α2-blockers
Although "alpha blocker" generally refers to α1-blockers, there are also α2-blockers, which are antagonists to the α2 adrenergic receptor. Examples include yohimbine, benzylpiperazine, rauwolscine and idazoxan.
References
- DrugDigest - Alpha blockers
- RxList.com - Tamsulosin
- MeSH alpha-Adrenergic+Blockers
|
||||||||||||||||||||
|
|||||||||||||||||
Wikipedia content modification information:
- This page was last modified on 25 April 2008, at 14:32.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Alpha blocker".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.