Tasimelteon will be given in two ways; orally (by mouth) as a 20 mg capsule and intravenously (I.V.) by infusion through a catheter (not an injection) into a vein. The oral administration is approved by the FDA. The I.V. administration is considered investigational as it has not been approved by the FDA. This will be the first time tasimelteon will be given to humans by intravenous (I.V.) injection.