A Safety Study of Xolair (Omalizumab) in Patients With Chronic Idiopathic Urticaria (CIU) Who Remain Symptomatic Despite Treatment With H1 Antihistamines, H2 Blockers, and/or Leukotriene Receptor Antagonists

Omalizumab was supplied as a lyophilized, sterile powder in a single-use vial.

Placebo was supplied as a lyophilized, sterile powder in a single-use vial without study drug.

Participants were required to maintain stable doses of their pre-randomization combination therapy with an H1 antihistamine and either an H2 blocker or leukotriene receptor antagonist, or all 3 drugs in combination, throughout the 24-week treatment period and 16-week follow-up period of the 40-week study.

Participants were provided with diphenhydramine 25 mg for itch relief on an as-needed basis, up to a maximum of 3 doses within 24 hours for the duration of the 40-week study.