Changing rapidly from finasteride to minoxidil or viceversa will mantain the hair conserved due to the first treatment?

In my opinion, you should be using both finasteride and minoxidil. Finasteride is an excellent medication to decrease DHTand may decrease loss due to genetic causes. Minoxidil affects the cycling of the hair and will usually increase hair thickness. Some people will get regrowth. The combination of the two drugs is more effective than either alone. Hope this helps. Good luck.

Probably not....Minoxidil has less effectiveness than finasteride. In your scenario, switching from finasteride to minoxidil would likely lead to hair loss. 

These two drugs work very differently and you must maintain their use and not play switching games without negatively impacting your problem. Stick to a play, hopefully worked out with a good doctor so that you know where you are going and when you get there. I am a believer in targeting goals and then achieving them.