US pharmaceutical giant Johnson & Johnson has been ordered to pay A$11.8 billion in damages for failing to warn that its psychiatric drug, Risperdal, could cause abnormal breast growth in men.

Nicholas Murray told a court in Philadelphia that the drug, normally prescribed to treat schizophrenia and bipolar disorder, had made him grow breasts.

His attorneys, Tom Kline and Jason Itkin, argued the drug was linked to the incurable condition known as gynecomastia, and accused Johnson & Johnson of making billions of dollars while illegally marketing and promoting the drug.

“(Johnson & Johnson is) a corporation that valued profits over safety and profits over patients,” they said in a statement.

But Johnson & Johnson immediately challenged the ruling, describing the damages as “grossly disproportionate” in a statement.

“The company is confident (the ruling) will be overturned,” it said. “We will be immediately moving to set aside this excessive and unfounded verdict.”

Johnson & Johnson said the court’s exclusion of key evidence left it unable to present a meaningful defence, including what they said was a drug label that “clearly and appropriately outlined the risks associated with the medicine” or Risperdal’s benefits for patients with serious mental illness.

“Further, the plaintiff’s attorneys failed to present any evidence that the plaintiff was actually harmed by the alleged conduct,” it added.

Thousands of lawsuits have been filed over the drug, including in Pennsylvania, California and Missouri, but Mr Kline and Mr Itkin said this was the first time a jury had decided whether to award punitive damages and had come up with an amount.

Risperdal was approved for the treatment of adults by the US Food and Drug Administration in 1993 and brought in about A$1 billion in sales in 2018.

- With wires