The approval is for Metronidazole in strengths of 250 mg and 500 mg, which are therapeutically equivalent to Flagyl Tablets of corresponding strengths of GD Searle LLC, the company said in a filing to the BSE.
The drug is an anti-infective agent used to treat a variety of bacterial and protozoal infections.
The product will be commercialised from Unichem's Ghaziabad plant. Active pharmaceutical ingredient Metronidazole used for this ANDA is also made in-house at Roha plant, it said.
At present, around six other companies have generic approvals for the US market and the estimated market size is over $100 million, the company added.
Shares of Unichem Laboratories were trading at Rs 216 per scrip in the afternoon trade, up 0.87 per cent from the previous close, on the BSE.