Plasma levels following intranasal and intravenous administration of human interferon-beta to rabbits.

Rabbits were given single doses (2 x 10(6) IU) of human fibroblast interferon (HuIFN-beta) by the following routes of administration: (a) intravenous injection, (b) dropwise intranasal administration of a liquid dosage form, and (c) spraywise intranasal administration of a powder dosage form. Following the intravenous injection, plasma HuIFN-beta concentrations declined rapidly in a biphasic manner in agreement with a two-compartment model, whilst concentrations following the intranasal administrations conformed to a one-compartment model. Maximum plasma levels and the areas under the plasma concentration-time curve (AUC) in response to dose were studied in the case of the spray administration, and found to be proportional to dose. The systemic bioavailability of HuIFN-beta (administered with sodium glycocholate and excipients) via the nasal routes was about 3% of that via the intravenous route. The elimination half-lives did not differ significantly between these two routes of administration.