The US state of Missouri has filed a lawsuit against four pharmaceutical companies, alleging that they inflated Medicaid prescription drug prices over the last decade.

US federal law requires companies making medicines to provide Medicaid with the average wholesale prices of products that they wish to be reimbursed by the programme. Missouri is claiming that Boehringer Ingelheim’s Roxane Laboratories unit, Mylan Laboratories, Teva Pharmaceutical Industries and Watson Pharmaceuticals set these prices too high, boosting the state’s drug bill by $19 million dollars.

"By reporting inflated prices that were then used to calculate Medicaid reimbursement, the companies were defrauding taxpayers in order to increase their market shares," said Attorney General Jay Nixon in a statement.

Nixon is seeking penalties and triple damages to reimburse Medicaid for the alleged overpayments and for the court to order that the companies stop the practice.

This action is only the latest in a series of similar cases brought by other states against pharmaceutical companies, and all four of these companies have been accused in the past. Earlier this year, 48 companies were named in a suit brought by the state of Illinois alleging they fraudulently inflated the average wholesaler prices for their medicines for more than 10 years.

Meanwhile, Missouri filed similar suits in May against two other pharmaceutical companies, Dey Inc and Schering-Plough subsidiary Warrick Pharmaceuticals, for similar schemes. That suit is still pending.