King Pharmaceuticals said that rival drugmaker Alpharma had rejected a $1.4bn unsolicited takeover offer it made this month, prompting the suitor to reveal details of the bid publicly in an attempt to pressure Alpharma into a deal.

King, which offered to pay $33 per share in cash for Alpharma, is looking to build out its suite of pain management drugs and capitalise on Alpharma’s pipeline of drugs, which is expected to bring drugs to the market within the next few years.