I have completed bachlor of pharmcay in india from rajiv gandhi university... so, now I want to do doctor of pharmacy in usa... so, how many years ill have to study more in usa?? Will I get any credit of my b.pharm that I did in india??

I can not speak for India, but I had a friend who was a doctor in mexico, he got no credit what so ever here in the US and had to go though school all over again.

My brother is a pharmacist and the actual dr program took him 4 years. It's not going to matter that you already have classes probably.