Page 214 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioTechnology

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Encyclopedia of Physical Science and Technology EN011J-141 July 31, 2001 15:14

Pharmaceuticals, Controlled

Release of

Giancarlo Santus Richard W. Baker
Recordati Industria Chimica e Farmaceutica S.p.A. Membrane Technology and Research, Inc.

I. Introduction/History
II. Methods of Achieving Controlled Release
III. Important Controlled Release Products
IV. Future Directions

GLOSSARY the skin and is absorbed into the blood circulatory
system.
Biodegradable polymers Materials that undergo slow Zero order delivery (of drug) Constant drug delivery
chemical degradation in the body, finally degrading to over a certain period of time.
low-molecular-weight fragments that dissolve or are
metabolized.
Controlled release systems Devices that meter delivery THE OBJECTIVE OF CONTROLLED drug delivery
of drugs or other active agents to the body at a rate devices is to deliver a drug to the body at a rate predeter-
predetermined by the system design and are largely mined by the design of the device and independent of the
unaffected by the surrounding biological environment. changing environment of the body. In conventional medi-
Enteric coatings pH-Sensitive materials used to delay cations, only the total mass of drug delivered to a patient is
dissolution of tablets in the acid environment of the controlled. In controlled drug delivery medications, both
stomach but allow rapid dissolution when the tablet the mass of drug and the rate at which the drug is delivered
reaches the more neutral pH environment of the gas- is controlled. This additional level of control enhances the
trointestinal tract. safety and efficacy of many drugs. Often a membrane is
Microcapsules Small, drug-containing particles with di- used to moderate the rate of delivery of drug. For example,
ameters between 50 and 1000 µm. in some devices, a membrane controls permeation of the
Targeted drug delivery Delivery of a drug directly to the drug from a reservoir to achieve the drug delivery rate re-
body site where the drug has its biological effect. quired. Other devices use the osmotic pressure produced
Transdermal patches Drug-containing laminates at- by diffusion of water across a membrane to power minia-
tached to the skin with an adhesive. Drug contained ture pumps. In yet other devices, the drug is impregnated
in the laminate migrates from the patch through into a polymer material, which then slowly dissolves or

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