**Acknowledgement**

Cook Ireland Ltd. is gratefully acknowledged for the financial support and the stent supply.

#### **4. References**

144 Polyurethane

inducing patient discomfort or pain.

a recidivist calculosis.

require the following properties:

minimum toxic one;

endourological requirements.

**Author details** 

**Acknowledgement** 

Valentina Cauda

Furio Cauda

Being biocompatible and preventing cytotoxicity;

subsequent patient hospitalization; Effectively incorporating a therapeutic agent;

Preventing the patient discomfort and pain;

*Urology division, Koelliker Hospital,Turin, Italy* 

These considerations were no more valid when the patient was a stone-former. Indeed, the recidivist calculosis induced a continuous deposition of biofilm and salts at the stent surface, thus strongly reducing the effect of the surface modification in preventing encrustation. In addition, the stents were more stiff and brittle after already one month of insertion, thus

It was noteworthy that both the formation of biofilm and inorganic encrustation and the success of the stent indwelling depended more significantly on the patient's pathology (i.e. stone former or not) than on the indwelling time. For these reasons, implanting a stent for a period of time longer than one month was feasible. A surface-treated polyurethane stent was also preferable with respect to the untreated PU one. However, frequent stent exchange, regardless of the surface treatment, is a general recommendation for patients suffering from

As a future outlook, new studies should expand in the direction of bio-degradable drugeluting polymeric stents. The preparation of such highly engineered ureteral stents should

Being fully biodegradable to avoid the complications of the stent removal and the

Releasing the required amount of drug, between the minimum effective level and the

Being deliverable and visible, with adequate radiopacity (or the presence of radiopaque

We envision that such a commitment will require a strong interdisciplinary background, thus combining the fields of material science and technology to the clinical and

markers) to enable precise positioning under X-ray fluoroscopic guidance.

*Center for Space Human Robotics CSHR@Polito, Italian Institute of Technology, Turin, Italy* 

Cook Ireland Ltd. is gratefully acknowledged for the financial support and the stent supply.

Providing effective urine drainage without the formation of bacterial biofilm;

Showing the capability to release the drug in a time-controlled manner;


Lingeman, J. E., et al. (2003). Use of a temporary ureteral drainage stent (TUDS) after uncomplicated ureteroscopy: results from a phase II clinical trial.J. Urol. Vol. 169, No 5,pp. 1682-1688.

**Chapter 8** 

© 2012 Batyrbekov and Iskakov, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Batyrbekov and Iskakov, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Polyurethane as Carriers** 

**of Antituberculosis Drugs** 

Yerkesh Batyrbekov and Rinat Iskakov

http://dx.doi.org/10.5772/35896

**1. Introduction** 

Additional information is available at the end of the chapter

preparations is use of PU as the carriers in drug delivery systems.

Polyurethanes (PU) are an important class of polymers that have found many applications as biomaterials due to their excellent physical properties and relatively good biocompatibility. Basically, PU may be produced by two chemical processes: by polycondensation of a diamine with bischloroformates or by reaction between a diol and a diisocyanate. Many biomedical devices are made from segmented PU such as catheters, blood pumps, prosthetic heart valves and insulation for pacemakers (Lelah & Cooper, 1986, Lamba et al., 1997). A promising approach for the development of new controlled-releasing

Drug delivery systems have been progressively developed in the field of therapeutic administration owing to their advantages: providing drug concentration over a period of prolonged action, decreasing the total therapeutic dose and reducing the undesirable side effects, and, hence, improving the pharmaceutical efficiencies. These are achieved by the use of the controlled-release drug delivery systems (Hsien, 1988). Controlled release dosage forms are consist of the pharmacological agent and the polymer carrier that regulate its release. In general two types of drug delivery systems have been used: diffusion-controlled systems and dissolution-controlled systems. In the first cause the drug is usually dispersed or dissolved in the solid reservoir or membrane and the kinetics of drug release are generally controlled by diffusion through the polymer. In the second cause the drug are generally incorporated into a water-soluble or water-swellable polymer and the release of drug is controlled by swelling and dissolution of polymer. In both the causes polymer function is a principal component which controls the transport and the release rate of drug molecule. To be a useful drug carrier, a polymer needs to possess certain features. The polymeric carrier has to be non-toxic, non-immunogenic and biocompatible; the carrier must contain an effective dose of active agent; the material of system must be biodegradable and

