Thiolated polycarbophil

More recently, polycarbophil-cysteine conjugates (thiolated polycarbophils) have been found to increase the permeation of some drugs. Hornof and Schnurch [94] found that the polycarbophil-cysteine conjugates increase the permeation of sodium fluorescein (2.2-fold) and dexamethasone phosphate (2.4-fold). The unmodified polymer... 

Clausen, A.E. and Bernkop-Schnurch, A. (2000) In vitro evaluation of permeation-enhancing effect of thiolated polycarbophil. J. Pharm. Sci. 89 1253-1261... 

Further, the enhanced transport of the P-gp substrate acyclovir across excised rat intestinal mucosa and Caco-2 monolayers in the presence of thiolated chitosan was found to be due to efflux pump inhibition (Palmberger et al. 2008). Co-administration of paclitaxel and thiolated polycarbophil significantly improved paclitaxel plasma levels and led to a more constant pharmacokinetic profile and reduced tumour growth in mammary cancer-induced rats (Foger et al. 2008). 

A sustained drug release is favourable for drugs with short elimination half-life. It can be controlled by hydration and diffusion mechanisms or ionic interactions between the drug and the polymeric carrier. In the case of diffusion control the stability of the carrier system is essential, as its disintegration leads to a burst release. Therefore, the cohesiveness of the polymer network plays a crucial role in order to control the release over several hours. Due to the formation of disulphide bonds within the network thiomers offer adequate cohesive stability. Almost zero-order release kinetics could be shown for insulin embedded in thiolated polycarbophil matrices (Clausen and Bernkop-Schnurch 2001). In the case of peptide and protein drugs release can be controlled via ionic interactions. An anionic or cationic polymer has to be chosen depending... 

Clausen, A. E. and Bernkop-Schnurch, A. Development an in vitro evaluation of a peptide drug delivery system based on thiolated polycarbophil. Pharm. Ind. 2001 63, 312-... 

Kast CE, Guggi D, Langoth N, Bernkop-Schnurch A. Development and in vivo evaluation of an oral delivery system for low molecular weight heparin based on thiolated polycarbophil. Pharm Res 2003 20(6) 931-936. 

Bernkop-Schniirch, A., G. Walker, and H. Zarti. 2001. Thiolation of polycarbophil enhances its inhibition of intestinal brush border membrane bound aminopeptidase N. J Pharm Sci 90 1907. 

Bernkop-Schnurch A, Marschtitz MK (1997) Development and in vivo evaluation of systems to protect peptide drugs from aminopeptidase N. Pharm Res 14 181-185 Bernkop-Schnurch A, Paikl C, Valenta C (1997) Novel bioadhesive chitosan-EDTA conjugate protects leucine enkephalin from degradation by aminopeptidase N. Pharm Res 14 917-922 Bernkop-Schnurch A, Thaler S (2000) Polycarbophil-cysteine conjugates as platforms for oral (poly)peptide delivery systems. J Pharm Sci 89 901-909 Bernkop-Schnurch A, Walker G, Zarti H (2001) Thiolation of polycarbophil enhances its inhibition of intestinal brush border membrane bound aminopeptidase N. J Pharm Sci 90 1907-1914... 

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