One of the country’s largest health insurers has sued a number of pharmaceutical companies, accusing them of running a price-fixing cartel of common generic drugs. Humana Inc. has accused the companies of colluding on the prices of generics to the detriment of health insurers and plan participants that have to pay for these drugs. The lawsuit comes after 45 states signed on to a lawsuit last year over an alleged scheme among generic drug manufacturers to fix the price of some 300 medications.