The stock lost 2.49 per cent to end at Rs 1,304.45 on BSE. During the day, it declined 2.82 per cent to Rs 1,300.05 -- its 52-week low.
At NSE, shares of the company went down by 2.58 per cent to close at Rs 1,303.80.
The company's market valuation too declined by Rs 1,497.42 crore to Rs 58,913.58 crore.
The stock was the worst hit among the bluechips on both the indices, Sensex and Nifty.
"Recently, the company's manufacturing facility underwent an inspection by the USFDA...Subsequently to that USFDA issued Form 483 citing three observations," Lupin Ltd had said in a regulatory filing on Friday.
As per the USFDA, observations are made in Form 483 when investigators feel that conditions or practices in the facility are such that products may become adulterated or render injuries to health.
The FDA Form 483 notifies the company's management of objectionable conditions.