Drugmaker Merck has told employees it can’t reach its goal of cutting up to 13,000 jobs by 2015 just by eliminating vacant jobs, so it is speeding up layoffs in the United States. According to an internal memo, by the end of October Merck will notify employees losing their jobs in sales and other departments. When Merck announced its earnings on July 29, it said the cuts were needed because generic competition next year will hurt its top-selling drug, asthma and allergy medicine Singulair.