Controlled Drug Release Composite Solid

The device can be a flat disk that is implanted under the skin, or many microspheres that can be injected into the body cavities. The device must not cause adverse reaction from the body, such as bio-incompatibility and inflammation, and the polymer should disintegrate into harmless products that are easily absorbed into the body s metabolism. 

The requirement of 3 mg/day of carmustine over 20 days means a load of up to 60 mg in a device. Most formulations would suggest no higher than a 10% load of drug in the polymer matrix, so that the entire drug depot would be approximately 0.6 mL in volume. This is a very modest size disk, of about 0.1 x 2.5 x 2.5 cm. Or this amount of drug can be packaged into numerous injectible microspheres of 300 ttm 

Making prototypes and laboratory testing of polymer disks are projects that require limited cost and time duration. Certification by the FDA, on the other hand, is a long drawn out and costly process, where animal tests are followed by three phases of clinical trials, which have been described elsewhere (e.g. Suffness 1995). When the results are assessed and evaluated, a brand new product that costs more than 100 million can also run into many unforeseen problems, which makes many financiers very cautions. One of the biggest unknowns is who would pay for this costly new form of medication, and whether the medical insurance companies and Medicare would approve payment. This is the reason why so many information technology products, such as digital cameras and spreadsheets, are launched quickly, as they require much less capital to start and do not require FDA clearance. 

The current price of a pouch with eight wafers is 9600. 

Now let us do a bit of reverse engineering, and take this design apart and see why it makes sense, which would be helpful in designing other devices. No reason is given for the formulation of eight wafers, each with the thickness of 1 mm and 1.45 cm 

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Figure 5.2 Drug dissolution process from suspension type solid dispersions (a) polymeric carrier-controlled dissolution polymer dissolution precedes that of the drug (large spheres), and the drug subsequently partially dissolves (small spheres) into the hydrated layer (shaded area) before release into the dissolution medium, and (b) drug-controlled dissolution whereby drug release precedes dissolution of the carrier and is essentially independent of it. It should be noted that the same mechanisms apply in the case of amorphous solid solution type composite phases. Reprinted with permission from [22], Copyright 2002 Elsevier.

As previously noted, the use of solid dispersions to improve the solubility of poorly water-soluble drugs dates back to 1961.Pharmaceutical composition with good dissolution and bioavailability can be formulated from solid dispersions of pharmaceutically active ingredients. Solid dispersions also can be used in controlled-release formulations. 

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