London : European drug makers, faced with increasing competition from cut-price copies of complex biotech drugs, cautioned doctors to take care when switching patients from an established product to a so called biosimilar version.

The complex nature of biological medicines, which are made inside living cells, means copies can never be exactly the same as the original. But a growing number of such drugs have now been approved in Europe as similar enough to do the job.

The European Medicines Agency has to date approved two dozen biosimilars against just four in the United States.

Late last month the first biosimilar cancer drug hit the European the market, with the launch of Celltrion's Truxima, a copy of Roche's blood cancer treatment Rituxan or MabThera.

Truxima has been approved in all of Rituxan/MabThera's indications and governments around Europe are keen to see it used widely, in order to curb rising drug bills.

Three industry associations representing branded drug firms, however, said in a joint statement that doctors should look at the circumstances of each individual patient before switching them from established drugs to cheaper biosimilars.

"It is vital for a physician to balance the level of evidence against the level of risk or uncertainty in each particular case," the EFPIA, EBE and IFPMA associations said.

"A 'one size fits all' approach is not appropriate."