Alpha-blockers, α-blockers, or α-adrenergic-antagonists are pharmacological agents that act as receptor
antagonists of α-adrenergic receptors.
Classification α1-blockers or antagonists act at α1-adrenoceptors
α2-blockers or antagonists act at α2-adrenoceptors When the term "alpha blocker" is used without
further qualification, it sometimes refers to α1-blockers, and sometimes refers to agents
that act at both types of receptors.
Examples of non-selective α-adrenergic blockers include:
Phenoxybenzamine Phentolamine
Tolazoline Trazodone
Typical and atypical antipsychotics Selective α1-adrenergic blockers include:
Alfuzosin Prazosin
Doxazosin Tamsulosin
Terazosin Silodosin
Selective α2-adrenergic blockers include: Atipamezole
Idazoxan Mirtazapine
Yohimbine The agents carvedilol and labetalol are both
α- and β-blockers.
Uses α-Blockers are used in the treatment of several
conditions, such as Raynaud's disease, hypertension, and scleroderma.
α-Blockers can also be used to treat anxiety and panic disorders, such as generalized anxiety
disorder, panic disorder, or posttraumatic stress disorder.
While most commonly used to treat hypertension, they are also often used to treat the symptoms
of BPH.
Alpha-2 adrenergic receptor agonists, such as clonidine and guanfacine, act as noradrenergic
autoreceptors to inhibit the firing of cells in the locus ceruleus, effectively reducing
the release of brain norepinephrine.
Clonidine has shown promise among patients with Anxiety, Panic and Posttraumatic Stress
Disorder aka PTSD in clinical trials and was used to treat severely and chronically abused
and neglected preschool children.
It improved disturbed behavior by reducing aggression, impulsivity, emotional outbursts,
and oppositionality.
The following Sleep disorders of Insomnia along with the Parasomnia disorders of Nightmares
and /or Night Terrors aka pavor nocturnus were all reported to be reduced.
Kinzie and Leung prescribed the combination of clonidine and imipramine to severely traumatized
Cambodian refugees with Anxiety, Panic and PTSD.
Global symptoms of PTSD were reduced among sixty-six percent and nightmares among seventy-seven
percent.
Guanfacine brand name Tenex produces less sedation than clonidine and thus may be better
tolerated.
Guanfacine reduced the trauma-related nightmares.
A recently completed randomized double-blind trial among veteran patients with chronic
PTSD showed that augmentation with guanfacine was associated with improvement in anxiety
and PTSD.
Prazosin aka Minipress is an alpha1-receptor antagonist.
Raskind and colleagues studied the efficacy of prazosin for PTSD among Vietnam combat
veterans in a 20-week double-blind crossover protocol with a two-week drug washout to allow
for return to baseline.
The CAPS and the Clinical Global Impressions-Change scale were the primary outcome measures.
Patients who were taking prazosin had a robust improvement in overall sleep quality and recurrent
distressing dreams.
In each of the PTSD symptom clusters the effect size was medium to large: 0.7 for reexperiencing
or intrusion, 0.6 for avoidance and numbing, and 0.9 for hyperarousal.
The reduction in CGI-C scores also reflected a large effect size.
Prazosin appears to have promise as an effective treatment for PTSD-related sleep disturbance,
including trauma-related nightmares, as well as overall Anxiety and PTSD symptoms.
See also Beta blocker
References