A recent decision by the US Supreme Court to remand a number of product liability lawsuits against US drugmaker Merck & Co to an appeals court has peaked the pharmaceutical industry’s interest.

Drugmakers hope the final ruling will finally clarify whether labeling decisions of the US Food and Drug Administration (FDA) protect companies from liability in state courts.

At stake in the ongoing litigation are hundreds of lawsuits from patients who claim Merck warned patients too late about serious bone fractures that could result from long-term use of the osteoporosis treatment Fosamax.

In its unanimous decision to remand the lawsuits, the Supreme Court instructed the appeals court to reweigh the evidence with the preemption labeling question at the forefront.

As the highest US legal instance determined that the question is about the law rather than about the drugmaker’s behaviour or the drug’s side effects, the decision will be made solely by a judge, without a jury. The appeals court had ruled initially that the question should be decided in a jury trial.

If Merck can show it was unable to comply with federal and state law simultaneously, Supreme Court Justice Stephen Breyer wrote in his majority opinion, it would not be liable for the failure to warn. However, he said a drug manufacturer would be hard pressed to prove that there is an actual conflict between state and federal law.

Although the FDA originally approved Fosamax in 1995, evidence emerged later that its long-term use of the drug could cause atypical femoral fractures as ordinary stress fractures progress over time into serious breaks. Patients had sued Merck under state law for failing to warn about those risks, but the company said the FDA's authority should preempt the claims.

According to the pharma trade journal Fierce Pharma, the drugmaker applied to change Fosamax’s FDA label in 2008, but the agency rejected the proposed warning simply specifying “stress fractures” as “inadequate." Rather than rewrite the label, Merck chose to withdraw it and did not warn about atypical femoral fractures until 2011, after the FDA forced the change based on its own analysis, the Supreme Court opinion said