Some patients report a decrease in IC/BPS using other antihistamines or medicines with antihistamine properties.

Antihistamines for IC/BPS

Though the most widely used antihistamine to treat IC/BPS is hydroxyzine, some people with IC/BPS find relieve from Claritin, Benadryl, and Singulair.


A mild anti-anxiety drug, hydroxyzine is available in two oral forms:

  • Hydroxyzine pamoate (Vistaril)
  • Hydroxyzine hydrochloride (Atarax)

Hydroxyzine affects mast cell degranulation, which is thought to play a part in some IC/BPS patients’ symptoms, especially those who have a history of allergies, migraines and irritable bowel syndrome. Hydroxyzine has been shown to improve these conditions, as well as IC/BPS. Hydroxyzine has been found to decrease:

  • Nocturia (night time voiding)
  • Daytime frequency
  • Pain (burning, pressure, painful intercourse)

Hydroxyzine pamoate has a slightly higher absorption rate. Hydroxyzine-HCL is a liquid form available for patients allergic to fillers or dyes used in the capsules or pills.

Dosage & Treatment Plan

Most patients start with a 10 to 25 milligram (mg) dosage of Atarax, Vistaril or their generic equivalent at bedtime every night for 1 week, and progress to 50 mg every night the second week. Ideally, within one month the dosage is increased to 75 mg, 50 mg taken at night and 25 mg taken during the day. Benefits of hydroxyzine may be seen within a few weeks to two months after initiating therapy.

To decrease the sedating side effects, some patients start hydroxyzine therapy at a 10 mg dosage, available with Atarax or in the liquid form, and work their way up, gradually, to a maximum dosage of 50 to 75 mg. After one year some patients are able to decrease their dosage by one-half without increasing symptoms. Others report that upon reducing their dosage, symptoms will return within a few days.

Potential Side Effects

Side effects include sedation, dry mouth, and increased depression in patients diagnosed with concurrent depression.

Take this medicine early in the evening initially to avoid excessive morning drowsiness. Most patients report that daytime drowsiness disappears within four to five days after beginning hydroxyzine therapy. Some patients report that with each dosage increase, the drowsiness period is shorter and not as intense.

Pregnancy & Warnings

Animal studies have found that fetal abnormalities occur at doses ten times higher than given to humans. It is not recommended that hydroxyzine be used if pregnant or nursing. Hydroxyzine is contraindicated for use in epileptic patients.