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Abstract
Dextrans are glucose polymers which have been used for more than 50 years as plasma
volume expanders. Recently, however, dextrans have been investigated for delivery
of drugs, proteins/enzymes, and imaging agents. These highly water soluble polymers
are available commercially as different molecular weights (M(W)) with a relatively
narrow M(W) distribution. Additionally, dextrans contain a large number of hydroxyl
groups which can be easily conjugated to drugs and proteins by either direct attachment
or through a linker. In terms of pharmacokinetics, the intact polymer is not absorbed
to a significant degree after oral administration. Therefore, most of the applications
of dextrans as macromolecular carriers are through injectable routes. However, a few
studies have reported the potential of dextrans for site (colon)-specific delivery
of drugs via the oral route. After the systemic administration, the pharmacokinetics
of the conjugates of dextran with therapeutic/imaging agents are significantly affected
by the kinetics of the dextran carrier. Animal and human studies have shown that both
the distribution and elimination of dextrans are dependent on the M(W) and charge
of these polymers. Pharmacodynamically, conjugation with dextrans has resulted in
prolongation of the effect, alteration of toxicity profile, and a reduction in the
immunogenicity of drugs and/or proteins. A substantial number of studies on dextran
conjugates of therapeutic/imaging agents have reported favorable alteration of pharmacokinetics
and pharmacodynamics of these agents. However, most of these studies have been carried
out in animals, with only a few being extended to humans. Future studies should concentrate
on barriers for the clinical use of dextrans as macromolecular carriers for delivery
of drugs, proteins, and imaging agents.