Implantable insulin controlled release systems

Implantable Insulin Controlled Release Systems for Treating Diabetes Mellitus... 

As a result of the shortcomings of current insulin therapy, much work has been directed toward developing polymeric controlled release systems that can be implanted or injected into the body to achieve glucose control in patients with diabetes. This chapter will review the history of such systems and will discuss ciurent technology and future trends for the sustained delivery of insulin for the treatment of diabetes mellitus. Several media serving as carriers include synthetic absorbable polymers, biomolecules, and ceramics. 

The integration of biosensors with drag delivery systems allows the controlled release of a drag substance in response to the levels of biological modulator. For example, the use of a glucose biosensor may be used to control the release of insulin from an implanted device or perhaps even an iontophoretic delivery device (see Chapter 8). 

There have been significant advances with regards to implantable delivery systems for the controlled release of insulin. Many of the systems previously studied have characteristics considered favorable, but no one system possesses all of the necessary attributes to make such systems a reality in humans. It is clear that biocompatibility and biodegradability are vital components to the ideal delivery system. Such systems do not require surgical removal upon exhaustion of drug and are seamlessly integrated into the... 

In addition to needles and syo inges, alternative techniques for insulin administration have been developed, some availing themselves of the kinetics of insulin insulin pens (supplied preloaded or with replaceable cartridges), external infusions and implantable pumps. These latter are convenient for cm accurately controlled continuously functioning biofeedback system, but pose difficulties for routine replacement in insulin deficiency. Therefore sustained-release (depot) formulations are used to provide an approach reasonably near to natural function and compatible with the convenience of daily living. An even closer approach is provided by the development of (at present inevitably expensive) miniaturised infusion pumps which can be used by reliable patients. 

In sustained-release implants, the general approach is to provide a barrier between the body fluid and insulin. This barrier can be microporous, where the rate of insulin release is diffusion-controlled, or it can be an erodible material that dissolves gradually and releases the entrapped insulin. By using mechanical stress or transmitted energy, externally modulated bolus release of insulin can be obtained. Even more sophisticated selfregulating (closed-loop) systems are also under development. 

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