Ranbaxy Laboratories (RANB.NS) also fell as much as 6 percent.
Media reports say surprise inspection by U.S. drug regulator on its Halol plant in Gujarat.
A company spokesman said, "We have no comments to offer".
"Majority of the inspections taking place nowadays are surprise inspection," Motilal said in a note to its clients.
Must wait for the final audit report to come, the Motilal note adds.
Also, Sun Pharma recalled 200 vials of a cancer drug in July.
Separately, the U.S. FDA said in May that Sun Pharma's response to the import ban on its Karkhadi plant in Gujarat was inadequate.