A peginterferon, short for pegylated interferon, is an interferon that is chemically paired with polyethylene glycol (PEG). Due to their longer half-life, peginterferons only need to be administered once a week (instead of about three times a week) for them to have the same effect as standard interferon therapy. The pegylation of the active substance causes the interferon to be released more slowly and excreted at a slower rate through the kidneys, therefore it remains in the blood for a longer period. By comparison, the half life of non-pegylated active ingredients is a few hours, whereas peginterferons can have a half-life of 40 to 80 hours.