Interferons are only available as injections, for example in the form of syringes pre-filled with injection solution. The following active substances (with trade names) belong to the interferon actives substances group: Interferon alfa-2a (Roferon-A) Peginterferon alfa-2a (Pegasys) Interferon beta-1a ( Avonex, Rebif ) Interferon beta-1b (Betaferon) Peginterferon beta-1a (Plegridy) Interferon gamma-1b (Imukin)