If you forget to take a dose of interferon beta-1b, take the missed dose as soon as your remember. Then start taking interferon beta-1b every other day again (do no take it two days in a row).
Interferon beta-1b comes in one strength, a vial that contains 0.3 mg of the drug, which makes a solution of 0.25 mg of interferon beta-1b per mL when mixed properly. Interferon beta-1b vials are for single use only. If your dose is less than the full vial, the remaining unused amount must be discarded (it cannot be saved for later).
Currently, there are no generic versions of interferon beta-1b licensed for sale (see Generic Betaseron or Generic Extavia).