Merck (NYSE: MRK), known as MSD outside the United States and Canada, today announced that the U.S. Food and Drug Administration (FDA) has approved ISENTRESS® (raltegravir), the company’s integrase inhibitor, for use in combination with other antiretroviral agents, for the treatment of HIV-1 in neonates – newborn patients from birth to four weeks of age – weighing at least 2 kg.