In a CSU patient transitioning from Xolair to Rhapsido, how long after the most recent Xolair dose do you start Rhapsido?

Since Rhapsido works as early as two weeks in most patients, I would recommend starting 1-2 weeks after the last Xolair injection to avoid breakthrough hives. This, of course, depends on whether the patient on Xolair is completely controlled or not. If not controlled, I would stop Xolair and start Rhapsido.

I would start as early as possible without concern of additional adverse events since mechanisms differ. Also, there are no known interactions or contraindications using both together, not that I recommend using both except is a very usually case. Although, onset of Rhapsido is rapid, it is not immediate, suggesting the early non-delayed start is optimal.