What is the treatment for flonase overdose?

None: For all intents and purposes, there is no such thing as Flonase overdosage. Taking too much over a long period of time could produce some steroid side effects, but that would require swallowing an entire bottle of Flonase daily for a few weeks. There is no way any insurance company would allow for a refill per day, and no one could afford that on an out-of-pocket basis.