The FDA has requested that Genentech add a boxed warning to its asthma drug Xolair (omalizumab). The boxed warning emphasizes that patients taking Xolair may develop anaphylaxis after any dose, even if there was no reaction to the first dose. Anaphylaxis may be delayed up to 24 hours after the dose is given. Patients should have emergency self-treatment with them in case anaphylaxis should occur.

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