US authorities have accused six pharmaceutical firms from the US, India and Australia of price-fixing.
It is alleged the companies conspired to raise the price of the antibiotic doxycycline and diabetes drug glyburide.
The civil lawsuit has been filed in 20 US states.
It follows criminal charges being brought against former executives at one of the accused firms.
The civil case follows a two-year investigation started by the office of Connecticut’s Attorney – and alleges that firms conspired over steak dinners and “girls nights out.”