I need to patent a drug for a second medical use (this drug is already had FDA approval for a …

What you describe is called “Repurposing.” There is a very good article on drug repurposing in http://scholarship.law.marquette.edu/cgi/viewcontent.cgi?article=1243&context=iplr > A. Repurposing Research To repurpose a drug, a scientist must demon…