From a fundamental perspective:
Ranbaxy's domestic business + "assured" pipeline (Para IV ANDA + FTF) valuation with a "modest" 14x-16x valuation comes to about Rs 280-320/share. So, stock can be expected to be bottoming out whenever it hits those sub-280 levels, 'cause all the bad news flow etc were happening the US, which can only get better from here on.
So, esp given the overall "run to safety" on a bear market to Pharma sector stocks, expect large scale institutional buying starting around these levels. Expect at spurt to 440-460 levels before the stock price stabilizes and news flow dependent again.