Extavia is available in pack sizes of: − 5 vials of interferon beta-1b and 5 pre-filled syringes containing solvent. − 15 vials of interferon beta-1b and 15 pre-filled syringes containing solvent. − 3-month multipack containing 45 (3x15) vials of interferon beta-1b and 45 (3x15) pre-filled syringes containing solvent.