UPDATE 2-FDA: data shows no clear heart risk from bone drugs

(Adds further company comments, detail on specific heart problem)

By Susan Heavey

WASHINGTON, Nov 12 (Reuters) - Clinical trial data from four drugmakers shows no overall risk of heart problems in patients taking certain drugs to treat osteoporosis, the U.S. Food and Drug Administration said on Wednesday.

The agency reviewed studies on Merck & Co's (MRK.N) Fosamax, Roche Holding AG's (ROG.VX) Boniva, Novartis AG's (NOVN.VX) (NVS.N) Reclast and Procter and Gamble Co's (PG.N) Actonel and found heart rhythm problems were "rare within each study, with most studies containing two or fewer events."

However, the FDA also said it was aware of conflicting findings in other studies and was considering whether conducting further studies to investigate the risk were feasible.

The drugs, part of a class of products known as bisphosphonates, aim to treat bone-weakening osteoporosis by increasing bone mass.

FDA officials began looking into concerns of abnormal heartbeats in women taking the drugs in October 2007 following reports of serious atrial fibrillation, a type of abnormal heartbeat, in the New England Journal of Medicine.

Since then, the agency has collected data on nearly 40,000 patients -- 19,687 given a bone drug and 18,358 given a placebo -- who were studied in clinical trials between six months and three years, it said.

"Across all studies, no clear association between overall bisphosphonate exposure and the rate of serious or non-serious atrial fibrillation was observed. Increasing dose or duration of bisphosphonate therapy was also not associated with an increased rate of atrial fibrillation," the FDA wrote.

While the agency plans to continue to monitor possible heart problems in patients taking such bone drugs, it concluded that doctors and patients should continue using the drugs as necessary.

Roche spokesman Christopher Vancheri said the company, and co-promoter GlaxoSmithKline Plc (GSK.L) (GSK.N), concluded their drug Boniva did not cause heart problems. Merck and Procter & Gamble representatives also said their internal review found no link.

Representatives for Novartis had no comment.

Bisphosphonates are also used to slow bone turnover in patients with Paget's disease and to treat bone metastases and lower blood calcium in cancer patients.

Other FDA-approved bisphosphonate drugs include Procter & Gamble's Didronel, Sanofi Aventis' (SASY.PA) (SNY.N) Skelid and Novartis' Aredia and Zometa, according to the agency. Sanofi also co-promotes Actonel.

Earlier this year, the FDA drew attention to possible severe pain in patients taking the drugs, already a known side effect.

The agency released its findings on its website here. (Additional reporting by Toni Clarke in Boston; Editing by Tim Dobbyn)