The 31-year-old Astapchuk had thrown 21.36m to claim the gold, while Adams threw 20.70 for the silver.
Ostapchuk tested positive for metenolone, and will see her excluded from the Olympics.
The Belarusian becomes the first person to be stripped of a medal at the Games.
As a result New Zealand move up to 15th in the medal table.
During the Games Team GB discus thrower Brett Morse, was cencured for tweeting.
“I’ve had a bad day, but it could be worse, I could look like Astapchuk,” before accusing her of doping, for which he later apologised.
However Morse has today tweeted: “For all you guys who sent me absuive message, via my website and twitter… Do one, Ostapchuck failed her test and her medal has been taken.”