The US Supreme Court has ruled that the duty of brand-name drugmakers to warn patients about side effects or complications with their products does not extend to the manufacturers of generic copies.

In a 5-4 ruling, the justices concluded that generics makers cannot be sued under state liability laws if they fail to warn patients of potential problems. This is because the federal Food and Drug Administration (FDA) has to approve any changes in the warning information supplied with the product.

The Justices added, however, that generics makers should alert the FDA and patients as soon as they receive reports of new side effects or complications with their products. 

The conflict between federal and state laws has created "conflict," said Justice Clarence Thomas, presenting the Court's conclusions in a case brought against generics makers Pliva and Actavis by two women who developed tardive dyskinesia after taking metoclopramide for acid reflux disorder.

"If the manufacturers had independently changed their labels to satisfy their state-law duty, they would have violated federal law," Justice Thomas added, but a dissenting judge, Justice Sonia Sotomayor declared that the court decision “leads to so many absurd consequences that I cannot fathom that Congress would have intended to pre-empt state law in these cases."

In 2009, the Supreme Court issued a ruling requiring brand-name drugmakers to have defence against failure-to-warn lawsuits brought under state product liability laws, but generics makers had argued that they should not be covered by this requirement because federal law obliges them to replicate the warning information issued by the originator companies. The Court accepted this argument.

The Generic Pharmaceutical Association (GPhA) yesterday welcomed the latest Supreme Court ruling, with the trade body's executive director, Bob Billings, noting that it had "appropriately recognised that current law leaves generic manufacturers with no alternative but to make certain that it products have labelling that is identical to the labelling of the reference brand product."

"As the Supreme Court recognised in this decision, assessing liability based on label content that is beyond the control of the generic manufacturer places the generic manufacturer in the impossible position of defending the content of a label that they are required by law to use but prevented by law from changing," he added.