What Causes Slurred Speech And Disorientation After Taking Nortripyline And Valium?

Question: A friend of mine has been taking methadone for quite some time and currently taking 140mg a day ( I think that is accurate). He also took valium (diazepam) during this entire time of taking the methadone for anxiety and stress in his life. No problems there.... Recently he has found out his father has a few days to live, his girlfriend is breaking up with him and he has to move out and find another place to live. He went to his doctor for some anti-depression medicine to help him cope and get a better attitude in place. The doctor knows he takes the methadone and valium and so he prescribed him Cymbalta to try first. Well insurance didn't cover it, so it would have been $130 to fill the script. He called the doctor back and the doctor changed the prescription to Nortriptyline and he started taking it Wed night. It says to take it before bedtime so he did. Well we saw effects from it immediately. He was okay at work yesterday (Thursday) and then took a couple valium and also the Nortripyline on his way home from work knowing he was about to go to bed. He gets home from work late due to being a car salesman and he has to work from morning until night and then has a little bit over an hour drive home from work. Well he was slurring speech, seemed disoriented, forgot conversations that we had, and had a hard time getting up for work this morning. He was sent home early from work today due to the same effects as the night before... slurred speech, seemed very down in the dumps and slow moving, disoriented, and would swap words around in his conversation that made it not make any sense. The General Manager knows him very well and became very worried about him and asked if he needed a ride home and to take a couple days to get used to the meds before coming back. I am worried about him and he has left two messages for his doctor today without a call back. He said he is going to take the depression meds tonight before he goes to bed but without the valium and see if that changes anything. He is wondering if the Benzo is affecting it and making him act so very weird and odd. I looked up interactions between the three drugs and found that all three cause drowsiness, tiredness, etc. Can you offer any suggestions or maybe he needs to swap to a different depression med. This is the first time he has ever taken depression meds and the doctor was just trying him out on one and I don't think this is the right one from how he has been acting. They say it takes two weeks to get in your system... but his actions changed immediately. Maybe it is 2 weeks for it to bring you around to a happy person if you are depressed, I don't know. I just want him to be back to the regular happy person he used to be and these three medications he is on right now are obviously reacting with each other. Remember, he has been taking the methadone and valium for at least a year with no problem. Now they throw in Nortriptyline and it seems to really throw it over the edge. Is there a better anti-depression medicine that will work with Methadone and Valium?? Thanks for all your help!