Rationale and Basic Principles

The general goal of drug delivery is to maximize the fraction of a drug dose delivered to target tissues and cells directly responsible for therapeutic effects and to Umit exposure of other tissues to the drug, as this exposure may elicit untoward effects. 

As discussed in Chapter 5, most biotechnology products (i.e., proteins and peptides) are formulated in sterile solution or suspensions designed for injection. A survey of the biotechnology products available in the United States reveals that over 90% of protein and peptide drugs are designed for parenteral administra- 

While some parenteral injections, such as intravenous administration, provide rapid and predictable access to the circulation and tissues, therapeutic proteins are rapidly cleared from the system, and thus such administrations may result in very short durations of action. Regardless of route of administration, therapeutic proteins may exhibit limited distribution outside of endothelial cells lining blood vessels. This may be advantageous for thrombolytic agents, such as tissue plasminogen activator, which is used for rapid fibrinolytic actions at 

Biotechnology and Biopharmaceuticals, by Rodney J. Y. Ho and Milo Gibaldi ISBN 0-471 -20690-3 Copyright 2003 by John Wiley Sons, Inc. 

To modulate the rate and extent of therapeutic protein exposure in target tissues, scientists have considered other routes of administration. These alternative routes of drug delivery will be discussed below. All available data suggest that protein bioavailability is expected to be low for nonparenteral routes of administration (i.e., less than 10%). 

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