Polycarbophil polymer

The term polyacrylates includes synthetic, high molecular weight polymers of acrylic acid (polyacrylic acid or PAA) that are also known as carbomers. They are either linear or (weakly) cross-linked (either by allyl sucrose (carbomers) or by divinyl glycol (polycarbophils)) polymers that are broadly applied in... 

Polycarbophil polymers are stable, hygroscopic materials. They do not undergo hydrolysis or oxidation under normal conditions. Heat aging at temperatures below 104°C for up to 2 hours does not affect the efficiency of the dry polymer. However, prolonged exposure to excessive temperatures can result in discoloration, reduced stability, and in some cases plasticization of the polymer. Complete decomposition occurs with heating for 30 minutes at 260°C. 

Heat may be generated if polycarbophil comes into contact with strong basic materials such as ammonia, sodium hydroxide, potassium hydroxide, or strongly basic amines. Polycarbophil polymers are not compatible with cationic polymers, strong acids, and high levels of electrolytes, as electrolytes tend to reduce the viscosity of polycarbophil-based gels. 

Polycarbophil polymers have a long history of safe and effective use in topical gels, creams, lotions, and ointments. They have been shown to have extremely low irritancy properties and are nonsensitizing with repeated usage. 

CM Lehr, YH Lee, VHL Lee. (1994). Improved ocular penetration of gentamicin by mucoadhesive polymer polycarbophil in the pigmented rabbit. Invest Ophthalmol Vis Sci 35 2809-2814. 

LueBen, H.L., Verhoef, J.C., Borchard, G., Lehr, C.-M., De Boer, A.G., and Junginger, H.E., Mucoadhesive polymers in peroral peptide drug delivery. II. Carbomer and polycarbophil are potent inhibitors of the intestinal proteolytic enzyme trypsin, Pharm. Res., 12 1293-1298 (1995). 

In vivo methods, which are few, measure the residence time of bioadhesives at the application site [47]. Techniques like y-scintigraphy, the perfused intestinal loop and radiolabeled transit studies using Cr-labeled bioadhesive polymer [48] and Tc-labeled polycarbophil [49] have been employed for this purpose. 

A novel concept of using bioadhesive polymers as enzyme inhibitors has been developed [97]. Included are derivatives of poly acrylic acid, polycarbophil, and car-bomer to protect therapeutically important proteins and peptides from proteolytic activity of enzymes, endopeptidases (trypsin and a-chymotrypsin), exopeptidases (carboxypeptidases A and B), and microsomal and cytosolic leucine aminopeptidase. However, cysteine protease (pyroglutamyl aminopeptidase) is not inhibited by polycarbophil and carbomer [97]. 

Lehr, C.M., et al. 1992. Effects of the mucoadhesive polymer polycarbophil on the intestinal absorption of a peptide drug in the rat. J Pharm Pharmacol 44 402. 

Luessen, H.L., et al. 1997. Mucoadhesive polymers in peroral peptide drug delivery. IV. Polycarbophil and chitosan are potent enhancers of peptide transport across intestinal mucosae in vitro. 

Polycarbophils and its derivatives Polyacrylic acid derivatives such as Carbomer 934P and Polycarbophil (B.F. Goodrich Specialty Polymers of Cleveland, Ohio) that are... 

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... 

Fig. 8.1 Correlation between pH of anionic polymer polycarbophil and its swelling behaviour pH 3 (A), pH 5(B), pH 7 ( ). Adapted from Bernkop-Schniirch and Steininger (2000)...

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... 

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