Does Vistaril (hydroxyzine) have alpha-blocking properties?

Vistaril (Hydroxyzine) and Alpha-Blocking Properties

Yes, hydroxyzine (Vistaril) does have alpha-adrenergic blocking properties, though this is not its primary mechanism of action. 1

Pharmacological Profile of Hydroxyzine

Hydroxyzine is primarily classified as a first-generation antihistamine with the following properties:

• Primary mechanism: H1-receptor antagonism
• Secondary mechanisms:
  • Alpha-adrenergic antagonism (alpha-blocking properties) 1
  • Anticholinergic effects
  • Sedative effects

Evidence for Alpha-Blocking Activity

The alpha-blocking properties of hydroxyzine are documented in recent medical literature:

• A 2024 case report demonstrated that hydroxyzine's alpha-adrenergic antagonism contributed to priapism when combined with risperidone (another medication with alpha-blocking properties) 1
• This case highlights the clinical relevance of hydroxyzine's alpha-blocking activity, as the combined alpha-blockade from both medications led to a significant adverse effect

Clinical Implications of Alpha-Blocking Properties

The alpha-blocking activity of hydroxyzine may contribute to:

1. Cardiovascular effects:

   • Potential for orthostatic hypotension, especially in elderly patients
   • Possible additive effects when combined with other medications that have alpha-blocking properties

2. Urological effects:

   • May affect urinary function
   • Can contribute to priapism when combined with other alpha-blockers 1

3. Neurogenic bladder effects:

   • Research shows hydroxyzine can inhibit neurogenic bladder mast cell activation 2
   • This effect may be partially mediated through its alpha-blocking properties

Comparison to Dedicated Alpha-Blockers

Unlike medications specifically classified as alpha-blockers (such as doxazosin, prazosin, and terazosin) 3, hydroxyzine's alpha-blocking effect is:

• Less potent
• Not its primary therapeutic mechanism
• Not typically used clinically for conditions where alpha-blockade is the desired effect

Precautions Related to Alpha-Blocking Activity

Due to its alpha-blocking properties, extra caution may be warranted when:

• Combining hydroxyzine with other medications that have alpha-blocking properties 1
• Using in elderly patients who may be more susceptible to orthostatic hypotension
• Administering to patients with cardiovascular conditions

Summary

Hydroxyzine does possess alpha-adrenergic blocking properties as part of its pharmacological profile, though this is secondary to its primary antihistaminic effects. This alpha-blocking activity can become clinically significant in certain scenarios, particularly when combined with other medications that have similar properties.