GASTROINTESTINAL PATCHES FOR ORAL DRUG DELIVERY -Part 3

The development of an adhesive bond between the patch and the intestinal wall can be visualized as a two step process.

• Initial contact between two surfaces.
• Formation of secondary bonds due to non-covalent interactions.

There are many theories proposed for the adhesion of the polymeric patches with the gastrointestinal mucosa. Wetting theory, diffusion theory, electronic theory, adsorption theory are some of those mechanisms.

The evaluation of the prepared patch can be done by both in vitro and in vivo techniques. Bioavailability, release pattern and bioadhesion of the patch can be determined by these techniques. In vitro evaluation includes methods like: shear stress management, detachment force measurement, mucoadhesion studies and adhesion force measurement. While x-ray techniques are the most important evaluation methods used for the in vivo studies.

As I explained earlier, gastrointestinal patch delivery systems possess many advantages compared to the conventional administrations. The application of GI patches has the following merits:

• This drug delivery system coated with mucoadhesive polymer binds to mucin molecules in the mucous lining and is therefore retained on the surface epithelium for extended period of time, hence increases the GI transit time and the mean residance time of the drug. Improvement in the mean residance time increases the extent of absorption.

• Stability problems of the drugs in the intestinal fluids can be overcome by the application of GI patches. Destructive effects of the gastric fluids on the drug can also be reduced to a greater extent.

• A site specific targeted delivery of the drug is possible with intestinal patches with a controlled diffusivity of the medicament.

• Histological studies showed no evidence of significant changes in the structure the intestine exposed to patches. There was no evidence of necrosis or specific inflammation.

• Insulin patches can localize insulin near the mucous membrane of the intestine. Hence there is no proteolytic degradation of the polypeptide by the luminal enzymes.

• Complex pulsatile release patterns can be developed with the aid of hydrogel gate type patches. This delivery method can mimic more naturally the way in which the body produces compounds such as insulin and some hormones.

Due to these advantages of GI patches some of the pharmaceutical and biotechnological companies are going behind them.BioSeren Tach Ltd, Japan has some GI patches under pipeline. The possible clients are leading pharmaceutical companies. BioSerenTach conducts pre-clinical study and clinical phase I study with the products based on the clientfs molecules together with the clients. BioSerenTach gets involved in research, development and production, and entrusts sales entirely to the clients.