Ranbaxy Laboratories, India’s biggest drug maker by revenue, said it expects sales to increase by at least 10 per cent in 2012 as it takes advantage of expiring drug patents in the United States, its biggest market.   Ranbaxy, which launched a generic version of cholesterol drug Lipitor in the US market in December, reported a fourth-quarter loss equivalent to $606 million. Sales, however, soared 79.2 per cent to $759.37 million in the quarter to Dec.31 from a year earlier, and were up 16.6 per cent at $2.02 billion for the full year.