GSK paid $85 million to U.S. doctors last year

* $56.8 mln for speaking engagements and advice

* $28.5 mln for U.S. clinical trials

LONDON, March 31 (Reuters) - GlaxoSmithKline (GSK.L) said on Thursday it paid $85.3 million to U.S. doctors and researchers in 2010 for a variety of services, including speaking fees, expert advice and work on clinical trials of its medicines.

The disclosure is the latest example of Big Pharma bowing to pressure for greater transparency, following concerns in the United States about commercial links between industry and healthcare professionals.

GSK has previously given details on payments to speakers, but not clinical trials.

In 2010, a total of 5,331 U.S. healthcare professionals were paid $56.8 million for speaking on behalf of GSK or giving it advice -- a modest pro rata decline on the $51 million paid in the last nine months of 2009. GSK only started detailing such payments from the second quarter of 2009.

Payments to U.S. doctors for clinical trials amounted to $28.5 million last year.

Speaking engagements, in which doctors are paid by drugmakers to discuss their medicines with groups of other physicians, have been among the most controversial industry marketing practices.

By law, companies are forbidden to promote their drugs for uses not cleared by the U.S. Food and Drug Administration. But some companies allegedly have greatly boosted prescriptions for their drugs by allowing or encouraging paid speakers to discuss such "off-label" use of their products. (Reporting by Ben Hirschler; Editing by Will Waterman)