shares of merck  co inc mrk slipped 182 to 10573 monday on what proved to be an allaround grim trading session for the stock market with the sp 500 index spx falling 015 to 385576 and dow jones industrial average djia falling 028 to 3181914 merck  co inc closed 976 short of its 52week high 11549 which the company reached on january 6th the stock underperformed when compared to some of its competitors monday as johnson  johnson jnj rose 096 to 15306 and pfizer inc pfe rose 119 to 3986