type of antidepressants like Sertraline
kind of antidepressants (like amitryptiline) when tapered together should be monitored closely as they have potential to cause a serious side effect called Seretonin Syndrome. Please make sure that you are being monitored for this by your doctor.
The 25mg dose is the smallest tablet that you get I think and hence if you are nto able to break into pieces, then the other way to take it would be to use it every other day. Since the half life of Sertraline is 26 hours and it takes usually 4-5 half lives for a drug to be completely out of the body, trying taking it on alternate days may make sense. I have never tried it in a patient before as they all could tolerate withdrawing from 25mg before well.
Another way will be to increase the amytriptyline dose and then take off the sertraline but again the risk of Seretonin syndrome.
ALL IN ALL, DOING IT UNDER THE EXPERT GUIDANCE OF A PSYCHIATRIST
IS THE BEST WAY FORWARD.