Dublin, Ireland-based Endo International has made a takeover bid for US drugmaker Salix Pharmaceuticals in an effort to thwart Valeant Pharmaceuticals International's $10 billion takeover offer.

Citing people familiar with the matter, the newspaper Wall Street Journal said the ethical pharmaceuticals and generics manufacturer had sent a private offer letter to Salix's board, offering $170 to $175 per share. Valeant has offered $158 per share.

If it torpedoes the existing agreement, Endo will have to cover the $356 million breakup fee, around $5.50 per share, that would be owed to Valeant if Raleigh, North Carolina-based Salix walks away.

Salix, with total revenue of $1.1 billion, makes a drug called Xifaxan that some analysts say could exceed $1 billion in annual sales if the Food and Drug Administration approves it to treat diarrhea caused by irritable bowel syndrome.

Last year the company had been close to a deal to sell itself to Allergan, at the time also being pursued by Valeant. Allergan has since been acquired by Actavis, which is in the process of changing its name to Alllergan.

In 2014, Endo broke up Auxilium Pharmaceuticals' deal to merge with QLT and instead paid $2.6 billion to buy Auxilium itself.