Additive delivery system

To facilitate in-plant compounding, most suppliers have developed systems which efficiently and repro-ducibly deliver a controlled additive package to a compound, using either a specialised concentrate or a masterbatch formulation. Some of the polymer manufacturers have also made available advanced additive delivery systems, which they have often developed originally for their own use (e.g. Eastman, Montell). 

Halogen-free flame retardants additive delivery systems... 

An example of such a product is Sterile Medroxyprogestrone Acetate Suspension used for its contraceptive property. Such an injection is designed to provide up to three months of contraceptive activity. Another such product is a depot injection of leuprolode acetate, an analogue of gonadatropin-releasing hormone (see Drug delivery systems). In this case, the product is a sterilized powder of microspheres to be suspended upon the addition of an appropriate diluent and intended for monthly injection. 

Kleimnan et al. 2008). In addition, synthetic siRNAs are also subject to degradation in vivo by nuclease activity. Besides side effects and instability, the efficient and specific delivery of the RNAi indncers to the target cell still requires optimization. Here we snmmarize the cnrrent statns of nncleic acid-based antiviral therapentics. The focns will be on antiviral strategies nsing antisense and RNAi technology. Additionally, antiviral ribozymes and aptamers will be discussed briefly, with a focus on recent studies. Gene therapy approaches and delivery systems are the subject of Chapter 11 of this book. 

Traditional Apparatus. As indicated earlier, liquid delivery systems for controlled rate addition of monomers and initiators have tended to rely upon constant speed piston pumps (19) in which volumetric control is achieved by manual adjustment of stroke length, and monitoring is by discharge from measuring cylinders. 

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

After the knowledge domain, the end users and the experts have been defined, a choice must be made for the software environment for the development of the expert system. In addition, the hardware for the development process as well as for the delivery system must be identified. Real application expert systems always require at least a mid-sized tool (see Section 43.7). 

Before treating the various classes of sustained- and controlled-release drug-delivery systems in this chapter, it is appropriate to note that drug delivery may be incorporated in other chapters where the various classes of drug products and routes of administration are discussed. In addition, the reader is referred to Chapter 14 on target-oriented drug-delivery systems. 

To use liposomes as delivery systems, drug is added during the formation process. Flydrophilic compounds usually reside in the aqueous portion of the vesicle, whereas hydrophobic species tend to remain in the lipid proteins. The physical characteristics and stability of lipsomal preparations depend on pH, ionic strength, the presence of divalent cations, and the nature of the phospholipids and additives used [45 47],... 

The delivery system needs to be discussed. This will include consideration of surface charges of the particles and of the device, the development of charges during filling of the product and during in-use streaming, and any relevant changes in effective particle size. Where the prototype device differs from the production device, additional data may be required. Dose uniformity and fine particle assessments at the relevant air flow rates should be reported. 

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