Merck is entering a new era, with sweeping changes across its executive suite and the spinoff off its women’s health and other businesses, a bid to enable both resulting companies to grow faster. The massive management makeover occurs as the drugmaker says hits to sales of many of its medicines amid lockdowns and other impacts from the coronavirus pandemic will lessen and sales will rise over the rest of the year. The drugmaker on Thursday said first-quarter profit dipped 1%, due to higher spending on research and medicine production and flat sales as the COVID-19 pandemic continued to limit doctor and hospital visits.