Alpha-blockers

α-blockers (alpha-blockers) or α-adrenergic-antagonists are pharmacological agents that act as receptor antagonists of α-adrenergic receptors (α-adrenoceptors).[1]

Classification

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:

Selective α1-adrenergic blockers include:

Selective α2-adrenergic blockers include:

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.[2]

α-blockers can also be used to treat anxiety and panic disorders, such as generalized anxiety disorder, panic disorder or posttraumatic stress disorder (PTSD). While most commonly used to treat hypertension (usually in conjunction with diuretics when other treatments are ineffective), they are also often used to treat the symptoms of BPH (benign prostatic hyperplasia). Alpha-2 adrenergic receptor agonists, such as clonidine and guanfacine, act at noradrenergic autoreceptors (presynaptic) to inhibit the firing of cells in the locus ceruleus, effectively reducing the release of brain norepinephrine.[3] 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.[4] The following Sleep disorders of Insomnia along with theParasomnia disorders of Nightmares and /or Night Terrors aka pavor nocturnus were all reported to be reduced.

Kinzie and Leung[5] 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.[6] 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[7] 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.[7] The CAPS and the Clinical Global Impressions-Change scale (CGI-C) were the primary outcome measures. Patients who were taking prazosin had a robust improvement in overall sleep quality (effect size, 1.6) and recurrent distressing dreams (effect size, 1.9). 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 (overall PTSD severity and function at endpoint) also reflected a large effect size (1.4). 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

References

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