The pharma company's shares ended at Rs 2,747.85, down 7.17 per cent on the BSE. During the day, the scrip plunged 7.94 per cent to Rs 2,725.
At the NSE, Glaxo's stock tanked 8.14 per cent to settle at Rs 2,725.
UK-based GlaxoSmithKline Plc (GSK) had in December last year announced an open offer to buy 24.33 per cent stake in its Indian arm GlaxoSmithKline Pharmaceuticals for a total consideration of Rs 6,389.02 crore.
Its stake will rise to 75 per cent if it gets the entire equity shares through the voluntary open offer.
The open offer began on February 18 and will close today.