Pooled PREEMPT data ( two studies : a 24-week , 2-cycle , double-blind , randomised ( 1:1 ) , placebo-controlled , parallel-group phase , followed by a 32-week , 3-cycle , open-label phase ) evaluated onabotulinumtoxinA ( 155-195U ) for prophylaxis of headaches in persons with CM ( 15days/month with headache 4h/day ) .