Thanks for posting your query.
The one important thing in the antideppressant use is that they must never be stopped suddenly and should be tapered only when your physician plans for it.
and they are interchangeable. So you should start the same dose of Duzela as Cymbalta and be watchful for any change because slight difference in rate of dose delivery can be there when you switch the preparation.
Hope I have answered your query.
If you have any questions I will be happy to answer.
Please close the query if you have no other questions.
Wish you a good health.