Shares of The Medicines Co. ( MDCO) sank 2.8% Tuesday after the company got a brokerage downgrade and set plans to sell stock. The Parsippany, N.J., drugmaker said early Tuesday it would sell 6 million shares through Bear Stearns and Merrill Lynch. Medicines Co. also suffered a UBS downgrade to reduce from neutral. "Our downgrade is based on valuation, as potential upside from current levels no longer supports a neutral rating," wrote UBS analyst Maged Shenouda in a research report Tuesday. UBS makes a market in the company's shares, which fell 93 cents to $32.82.