In pre-planned secondary analyses , a significant decrease in sweat chloride concentration occurred in the treatment groups between day 1 and day 56 ( lumacaftor 400 mg once per day group -9.1 mmol/L , p < 0.001 ; lumacaftor 600 mg once per day group -8.9 mmol/L , p < 0.001 ; lumacaftor 400 mg every 12 h group -10.3 mmol/L , p = 0.002 ) .