PEGylation is a pharmaceutical technology that involves the covalent attachment of polyethylene glycol (PEG) to a drug to improve its pharmacokinetic, pharmacodynamic, and immunological profiles, and thus, enhance its therapeutic effect. Currently, PEGylation is used to modify proteins, peptides, oligonucleotides, antibody fragments, and small organic molecules. Research groups are striving to improve the consistencies of PEGylated drugs and to PEGylate commercialized proteins and small organic molecules. Furthermore, the PEGylations of novel medications, like oligonucleotides and antibody fragments, are being pursued to improve their bioavailabilities. This active research in the PEGylation field and the continued growth of the biopharmaceutical market predicts that PEGylated drugs have a bright future.

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This review provides a compilation of the methods used to study real-time (37 degrees C) drug release from parenteral microparticulate drug delivery systems administered via the subcutaneous or intramuscular route. Current methods fall into three broad categories, viz., sample and separate, flow-through cell, and dialysis techniques. The principle of the specific method employed along with the advantages and disadvantages are described. With the "sample and separate" technique, drug-loaded microparticles are introduced into a vessel, and release is monitored over time by analysis of supernatant or drug remaining in the microspheres. In the "flow-through cell" technique, media is continuously circulated through a column containing drug-loaded microparticles followed by analysis of the eluent. The "dialysis" method achieves a physical separation of the drug-loaded microparticles from the release media by use of a membrane, which allows for sampling without interference of the microspheres. With all these methods, the setup and sampling techniques seem to influence in vitro release; the results are discussed in detail, and criteria to aid in selection of a method are stated. Attempts to establish in vitro-in vivo correlation for these injectable dosage forms are also discussed. It would be prudent to have an in vitro test method for microparticles that satisfies compendial and regulatory requirements, is user friendly, robust, and reproducible, and can be used for quality-control purposes at real-time and elevated temperatures.

, WI *This article represents the scientific opinion of many experts and, in particular, is derived from a series of workshops held under the auspices of the Federation International Pharmaceutique (FIP) and cosponsored by the Royal Pharmaceutical Society (UK), the Bundesverband der Pharmazeutischen Industrie (BPI), Colloquium Pharmaceuticum (Germany), the American Association of Pharmaceutical Scientists (AAPS, US), and the US Food and Drug Administration. It is

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This study shows that the N-terminus of octreotide is the preferred PEGylation site to prevent acylation in degrading PLGA microspheres. The mono-N-terminally PEGylated octreotide may possibly serve as a new source for somatostatin microsphere formulation.

Controlled release delivery is available for many routes of administration and offers many advantages (as microparticles and nanoparticles) over immediate release delivery. These advantages include reduced dosing frequency, better therapeutic control, fewer side effects, and, consequently, these dosage forms are well accepted by patients. Advances in polymer material science, particle engineering design, manufacture, and nanotechnology have led the way to the introduction of several marketed controlled release products and several more are in pre-clinical and clinical development.