Omnicare’s bid to acquire US-based PharmMerica Corp for $441m has been rejected, due to concerns over regulatory risks.

The nursing home sent a letter to PharMerica on Tuesday proposing the purchase of all outstanding shares of common stock for $15 a share in cash, a premium of 37% based on Monday’s closing price of PharMerica shares.

Omnicare said its deal was aimed at lowering healthcare costs in the US and helping customers manage and respond to ‘ongoing industry cost pressure’.

PharMerica confirmed that it had received and rejected the proposal, after consultation with its financial and legal advisors.

The firm said in a statement, “The PharMerica board of directors unanimously determined that the Omnicare proposal undervalues PharMerica and is not in the best interest of PharMerica or its stockholders.

“The board noted that the Omnicare proposal is subject to significant regulatory uncertainty, and, despite Omnicare’s non-specific assurances to the contrary, antitrust clearance is likely to be difficult to achieve and involve lengthy administrative and court proceedings,” the statement continued.

Omnicare disagreed with PharMerica’s analysis and urged the company to engage in ‘meaningful discussions’ over the proposal.

The company said, “We remain firmly committed to pursuing this transaction and continue to be very confident in our ability to consummate a transaction expeditiously.”