I Have Been On Valdroxan For A Week After Having

I have been on valdroxan for a week after having minor problems with cymbolta (otherwise it helped).
I am 74 and have had bad depression for over 30 yrs. I've tried all the other anti dep. on the market over time.
The depression is getting bad and I doubt that I'd last the 2 weeks to see if I had any benefit.
Q. How do I come OFF the valdoroxan and get back on the cymbolta.

Thanks