Melatonin alone and in combination increased the inhibitory PMS as assessed by the Numerical Pain Scale [ NPS ( 0-10 ) ] reduction during the CPM-TASK : -2.4 ( 2.04 ) melatonin + amitriptyline,-2 .65 ( 1.68 ) melatonin , and-1 .04 ( 2.06 ) amitriptyline , ( P < 0.05 ) .