Why is caution needed when starting or stopping satralizumab in patients taking warfarin, carbamazepine, phenytoin or theophylline?

Starting or stopping satralizumab warrants caution with warfarin, carbamazepine, phenytoin or theophylline because IL-6 suppresses CYP450 enzymes that metabolise these narrow-therapeutic-index medicines; doses may need adjustment, and satralizumab’s effects may persist for several weeks after stopping.