Bradley Pharmaceuticals ( BDY) agreed Tuesday to a $346 million buyout, a deal that sent shares of the small-cap dermatologics company soaring more than 20%.

Nycomed has agreed to pay $20 a share, a $4 premium over Monday's closing price of $16. Bradley's board approved the merger, which is now subject to shareholder vote. Such a duo would match Bradley with Nycomed's PharmaDerm division, adding to its dermatologics in the U.S.

Bradley formed a special committee of independent directors to evaluate strategic alternatives in May after CEO Daniel Glassman sought to take the company private for $360 million.

Privately held Nycomed, which expects the transaction to close in the first quarter, said combined annual sales of Nycomed US and Bradley amount to roughly $450 million.

Shares rose $3.73, or 23.3%, to $19.73 in recent trading.