From the Guidelines
Hydroxyzine is the preferred antihistamine for treating interstitial cystitis due to its ability to block histamine receptors, reducing inflammation and pain in the bladder, as well as its anti-anxiety properties, which can help with the stress component of the condition. The mechanism of action of hydroxyzine in treating interstitial cystitis involves blocking histamine receptors, which are believed to play a role in the inflammatory process of the condition 1. Histamine is thought to contribute to the inflammation and pain in the bladder, and hydroxyzine's antihistamine properties help mitigate these effects.
Typical dosing of hydroxyzine starts at 10-25mg at bedtime, which can be increased to 25-75mg daily as needed. Other antihistamines, such as first-generation antihistamines like diphenhydramine (Benadryl), may also provide some benefit, but hydroxyzine is preferred due to its additional anti-anxiety properties. Second-generation antihistamines like cetirizine (Zyrtec) or loratadine (Claritin) have less evidence supporting their use for this condition.
Some key points to consider when using hydroxyzine to treat interstitial cystitis include:
- Hydroxyzine works best as part of a multimodal approach to interstitial cystitis treatment, combined with dietary modifications, pelvic floor physical therapy, and sometimes other medications like pentosan polysulfate sodium (Elmiron) 1.
- Patients should be aware that drowsiness is a common side effect, which is why hydroxyzine is often taken at bedtime 1.
- Improvement may take several weeks to become noticeable, and patients should continue treatment as prescribed even if symptoms don't improve immediately.
- The evidence supporting the use of hydroxyzine for interstitial cystitis is of moderate strength, with some studies indicating that patients with systemic allergies may be more likely to respond to hydroxyzine 1.
From the Research
Mechanism of Action of Hydroxyzine
- Hydroxyzine, an antihistamine, has been shown to inhibit neurogenic bladder mast cell activation, which is a key component in the pathophysiology of interstitial cystitis 2.
- The mechanism of action of hydroxyzine is unrelated to its H-1 receptor antagonistic properties, and it is thought to reduce carbachol-induced serotonin release from rat bladder in vitro 2.
- Hydroxyzine's ability to inhibit bladder mast cell activation, along with its anticholinergic, anxiolytic, and analgesic properties, may explain its clinical efficacy in reducing interstitial cystitis symptoms 2, 3.
Efficacy of Other Antihistamines
- Not all antihistamines are effective in treating interstitial cystitis, as demonstrated by the lack of inhibitory effect of diphenhydramine on carbachol-induced serotonin release 2.
- Azatadine, a mixed H-1 receptor antagonist and 5-hydroxytryptamine-receptor antagonist, actually caused an increase in carbachol-induced serotonin release 2.
- Hydroxyzine's unique properties make it a useful treatment option for interstitial cystitis, and other nonsedating hydroxyzine analogues may provide potentially new therapeutic approaches for the condition 2.
Multimodal Therapy for Interstitial Cystitis
- Multimodal therapy, including oral pentosan polysulfate sodium (PPS) plus an antihistamine such as hydroxyzine, and a tricyclic antidepressant (TCA) such as amitriptyline, has shown benefit in treating interstitial cystitis 4.
- Behavioral interventions and intravesical instillation therapy are adjunctive measures that can promote symptom relief 4.
- Pharmacotherapies such as amitriptyline, hydroxyzine, and PPS are used to treat interstitial cystitis/bladder pain syndrome (IC/BPS), although the recent finding of pigmented maculopathy with chronic PPS is a concern 5.