Polymers ethylcellulose

Some tablets combine sustained-release and rapid disintegration characteristics. Products such as K-Dur (Key Pharmaceuticals) combine coated potassium chloride crystals in a rapidly releasing tablet. In this particular instance, the crystals are coated with ethylcellulose, a water-insoluble polymer, and are then incorporated into a rapidly disintegrating microcrystalline cellulose (MCC) matrix. The purpose of this tablet is to minimize GI ulceration, commonly encountered by patients treated with potassium chloride. This simple but elegant formulation is an example of a solid dosage form strategy used to achieve clinical goals. 

An improvement in this system is to coat the ion-exchange resin with a hydrophobic rate-limiting polymer, such as ethylcellulose or wax [43], These systems rely on the polymer coat to govern the rate of drug availability. 

Rekhi, G.S. and Jambhekar, S.S. (1995) Ethylcellulose - a polymer review. Drug Development and Industrial Pharmacy 21 61-77. 

FMC designs one such water-soluble coating for timed-release medications — Aquacoat ECD, a 30% by weight aqueous dispersion of ethylcellulose. This polymer is used to coat drug-layered beads that are delivered using gelatin capsules... 

Polyamide, collodion (cellulose nitrate), ethylcellulose, cellulose acetate butyrate or silicone polymers have been used for preparation of permanent microcapsules. This method offers a double specificity due to the presence of both the enzyme and a semipermeable membrane. Moreover, it allows simultaneous immobilization of many enzymes in a single step and the surface area for contacting the substrate and the catalyst is large. The need of high protein concentration and the restriction to low molecular weight substrates are the main limitations of enzyme microencapsulation. 

Ethyl butyrate, permeation in selected barrier polymers, 3 389t Ethylcellulose, 4 716, 724t 5 459-461 applications, 5 46 It liquid crystals, 5 385 physical properties, 5 460t production of, 10 590... 

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

Two polymers were incorporated in the inert matrix system ethylcellulose and polyvinyl chloride. The processes used to prepare tablets containing such polymers often include direct compression [4-6], wet granulation [7,8], coating [9-11] and, rarely, dry granulation [12]. 

The aim of this study is to analyse and choose the best process for a formula which contains an anti-inflammatory agent (diclofenac sodium), two inert polymer matrices (PVC, ethylcellulose) and two lubricants (magnesium stearate, talc). 

Aquacoat ECD (ethylcellulose polymer, acetyl alcohol, and sodium lauryl sulfate in water) Coating for tablets and capsules Repeat-dose toxicity with routine end points (90 days—oral rat) and reproduction toxicity (embryo-fetal study in rat) No adverse findings for general toxicity or reprotoxicity 29, 30... 

Materials that form a permeable membrane include fats, bee wax, carnauba wax, cetyl alcohol, cetylsteryl alcohol, zein, acrylic esters, silicone elastomers, and ethylcellulose (14). Aqueous dispersions of water-insoluble polymers are commonly used for sustained-release film coatings. Examples of commercially available aqueous polymer dispersions include Surelease-containing ethylcellulose, Aquacoat-containing... 

Block and graft copolymers were prepared by Akutin, Parlashke-vich, Kogan, Kalinina, and Menes (128) by the use of ultrasonics on solutions of fluorine containing polymers or polysiloxanes on one hand and polymethyl methacrylate, polyvinyl chloride, ethylcellulose on the other. 

Active sites created by an electric discharge method were being used for graft copolymerization by Akutin et al. (130). When a solution of a polymer in a suitable monomer is subjected to high voltage electric discharge polymerization of monomer is initiated as a result of the pressure impulses acting on the system. The authors studied the copolymerization of methyl methacrylate onto polyvinyl chloride, and of vinyl chloride onto ethylcellulose. 

A possible way to lower the costs of fibers and films of regenerated cellulose would be to run cellulose through a twin-screw ultrasonic extruder with a minimum of solvent and pass the extrudate through a stream of hot air to recover the solvent for reuse. This stronger cellophane could be used in place of many plastic films used today. A great number of derivates of cellulose have been made. Methyl, ethyl, carboxymethyl, hydroxyethyl, and hydroxypropyl ethers are made commercially today. These are used as water-soluble polymers, except for ethylcellulose, which is a tough plastic used in screwdriver handles and such. 

Prior to this discovery, in 1954 Silberberg and Kuhn (62) were first to study the polymer-in-polymer emulsion containing ethylcellulose and polystyrene in a nonaqueous solvent, benzene. The mechanisms of polymer emulsification, demixing, and phase reversal were studied. Wetzel and Hocks discovery would then equate the pressure-sensitive adhesive to a polymer-polymer emulsion instead of a polymer-polymer suspension. Since the interface is liquid-liquid, the adhesion then becomes one type of R-R adhesion (35, 36). According to our previous discussion, diffusion is not operative unless both resin and rubber have an identical solubility parameter. The major interfacial interaction is physical adsorption, which, in turn, determines adhesion. Our previous work on the wettability of elastomers (37, 38) can help predict adhesion results. Detailed studies on the function of tackifiers have been made by Wetzel and Alexander (69), and by Hock (20, 21), and therefore the subject requires no further elaboration. 

Ito A and Hwang S. Permeation of propene and propylene through cellulosic polymer membranes. J Appl Polym Sci 1989 38 483 90. Sridhar S and Khan A. Simulation studies for the separation of propylene and propane by ethylcellulose membrane. J Membr Sci 1999 159 209-219. 

To a very limited extent, other polymers have been coacervated by this process to form microparticles, i.e., ethylcellulose, cellulose nitrate, poly(methyl methacrylate), cellulose acetate phthalate, poly(acrylonitrile-co-styrene), and poly(styrene). " For some of these, liquid poly(butadiene) (8-10 kDa) was employed as a coacervating agent. 

Pennkinetic System Skye Pharma AG, Muttenz, Switzerland The system combines CR principles of ion exchange with membrane diffusion. The system is made up of an ion-exchange polymer-drug complex as a core material, which is subsequently coated with ethylcellulose to form a water insoluble but permeable coating. Release rates are relatively constant and unaffected by variable conditions of the GI tract. The system can be formulated in capsule form as well as suspensions. Delsym (Dextromethorphan), Corsym (Chlorpheniramine) and Cold Factor 12 (Phenylpropanolamine). 

---