PHARMACEUTICALS

Merck President Quits: The president and chief operating officer of the pharmaceutical giant stepped down for what were described as personal reasons. The world’s third-largest drug company said it will not immediately replace Richard J. Markham, whose duties will be assumed by other executives. Markham, a 20-year veteran of the firm, had been considered the leading candidate to replace Chairman P. Roy Vagelos, who is expected to retire next year.