"We have now received a communication from US FDA that they have determined that Ranbaxy has forfeited its 180 days exclusivity for esomeprazole magnesium delayed-release capsules," the company said in a BSE filing.
Esomeprazole is used for treatment of certain stomach and esophagus problems such as acid reflux and ulcers.
Ranbaxy said it "is disappointed with the result and is pursuing all available legal options to preserve its rights."
In November 2014, US FDA revoked its tentative approvals for Ranbaxy's generic anti-viral drug valganciclovir hydrochloride and esomeprazole magnesium delayed-release capsules 20 mg and 40 mg.
However it added that "its original decisions granting tentative approvals were in error because of the compliance status of the facilities referenced in the ANDAs at the time the tentative approvals were granted."
Shares of Ranbaxy were trading at Rs 700.15 apiece, down 0.86 per cent from its previous close on the BSE.
