Drug companies are spending record amounts on acquisitions in emerging markets, with China the most attractive target nation, reflecting sharply rising sales of western medicines in the country.

Overall expenditure by both overseas and domestic pharmaceutical companies in emerging markets has reached $20 billion so far this year, up two-thirds on the 2011 total, according Thomson Reuters data.

An analysis of year-to-date deals by law firm Freshfields Bruckhaus Deringer, published on Wednesday, showed China accounted for $6.8 billion of the total.

Spending by overseas acquirers alone in key growth markets is running at $3.5 billion so far this year, an increase of 95% on 2011.

The sharp upturn in emerging market activity contrasts with an overall decline in pharmaceutical mergers and acquisitions (M&A) worldwide to $146 billion from $225 billion last year.

After a flurry in 2011, which took deal-making back to pre-recession levels, drug companies been wary of hitting the takeover trail in a big way in Western markets in 2012.

"Instead, pharma investments in fast growing economies are gathering steam," said Freshfields corporate partner Jennifer Bethlehem.

"While M&A is an expensive remedy, 'pharmerging' markets are obvious investment choices for cash-rich drug companies."

Emerging markets are expected to account for the bulk of growth in the global pharmaceuticals market in the next few years, as sales in Europe and United States slow due to a wave of patent expiries.

China's drugs market, in particular, is forecast to grow by 15 to 18% annually to between $155 billion and $165 billion by 2016, making it the world's second-largest market after the United States, according to consultancy IMS Health.

Freshfields said it expected investment in China's pharmaceuticals sector to pick up further in 2013, following a smooth transition of political leadership in the country.