In order to achieve a zero-order release of protein drugs, we have develope
d a new drug delivery system using silicone, which is named the covered-rod
-type formulation. Preparation of the covered-rod-type formulation was cond
ucted under mild conditions without heat treatment or the use of organic so
lvents. The covered-rod-type formulation released human serum albumin (HSA)
or interferon (IFN) at a constant rate for 30-100 days in vitro without si
gnificant initial burst. When the IFN covered-rod-type formulation was impl
anted in nude mice, the serum IFN concentration was maintained at a constan
t level during the period of observation, i.e., 28 days. The covered-rod-ty
pe formulation enabled precise control of the release of the protein drugs
and would be expected to increase the duration of the drug effect and to re
duce the frequency of administration and side effects. (C) 2001 Elsevier Sc
ience B.V. All rights reserved.