Sorry to be a buzzkill, but there is no definitive answer to who-is-the-most-reactive-element-amongst-all, because it takes two to tango. One could ask which element is the most reactive with Sodium? The answer then is Fluorine, not Caesium. Or, perhaps you want to know which element is the most reactive with Nitrogen. Its Lithium! Shocker!
1 Day 1: reduce dosage of amitriptyline to 75 mg/day. 2  Day 8: reduce dosage of amitriptyline to 50 mg/day. 3  Day 15: reduce dosage of amitriptyline to 25 mg/day. 4  Day 22: reduce dosage of amitriptyline to 10 mg/day. Day 8: reduce dosage of amitriptyline to 50 mg/day. 2  Day 15: reduce dosage of amitriptyline to 25 mg/day. 3  Day 22: reduce dosage of amitriptyline to 10 mg/day. 4  Day 29: stop administration of amitriptyline.
For treating depression, the starting dose is amitriptyline 75 mg total daily (divided into two or three smaller doses). Or instead of several doses a day, the starting dose can be amitriptyline 50 mg to 100 mg once a day at bedtime. The dose can be increased slowly if necessary.