Drug formulations polymers

Small amounts of surfactants may be used to prevent aggregation of proteins and may enhance the refolding process when the dried protein dissolves. Buffers may also help to prevent aggregation of the dissolved drug. Similarly, polymers may be used as aggregation inhibitors or to form matrices. Chan et al. [86] prepared crystalline powders of recombinant human deoxyribonuclease with high fractions of sodium chloride. These powders were formulated as adhesive mixtures on lactose and mannitol and showed improved aerosolization behaviour compared to the pure protein. 

Bioadhesive formulations and microsphere delivery systems in particular have attracted much attention. As drug formulations are usually rapidly removed from the site of deposition by the mucociliary clearance, increasing the retention time of drug in the nasal cavity via bioadhesion can increase bioavailability [28], Bioadhesion may be defined as the ability of a material (synthetic or biological) to adhere to a biological tissue for an extended period of time. When applied to a mucous membrane, a bioadhesive polymer may adhere primarily to the mucus layer or epithelial cell surface in a phenomenon known as mucoadhesion [29,30]. The bioadhesive properties of a wide range of materials have been evaluated over the last decade. 

Recently, a new class of inhibitors (nonionic polymer surfactants) was identified as promising agents for drug formulations. These compounds are two- or three-block copolymers arranged in a linear ABA or AB structure. The A block is a hydrophilic polyethylene oxide) chain. The B block can be a hydrophobic lipid (in copolymers BRIJs, MYRJs, Tritons, Tweens, and Chremophor) or a poly(propylene oxide) chain (in copolymers Pluronics [BASF Corp., N.J., USA] and CRL-1606). Pluronic block copolymers with various numbers of hydrophilic EO (,n) and hydrophobic PO (in) units are characterized by distinct hydrophilic-lipophilic balance (HLB). Due to their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. In aqueous solutions with concentrations above the CMC, these copolymers self-assemble into micelles. 

Ju, T., Phillip, N., John, S., et al. HPMC-based extended-release matrices containing poorly-soluble compounds A mechanistic study of the effects of key formulation variables on drug and polymer release. AAPS Annual Meeting, San Francisco, CA, 1998. 

Given the considerable challenge of ocular drug delivery, i.e. short contact time and low drug bioavailability, mucoadhesives are attractive excipients in ophthalmic drug formulations. The presence of mucin in the eye allows bioadhesive polymers to thicken the tear film in the front of eye. 

Drug Formulation Approach Polymers/Bases References... 

Sheskey, P. J., and Hendren, J. (1999),The effects of roll compaction equipment variables, granulation technique, and HPMC polymer level on a controhed-release matrix model drug formulation, Pharm. Technol., 23, 90, 92, 94, 96, 98,100,102,104,106. 

A mqority of the devices for controlled administration of chemicals or drugs employ polymers in their formulation to serve as a vehicle and/or rate controlling element. The purpose of the polymer and the medianism by which it functions may vary in complexity, but clearly the sorption and diffusion of these chemicals in the polymer is frequently a central issue in product des and function. In addition, environmental stability and compatibUity along with mechanical behavior and process-ability are also important issues. Further, these sqiplications place unusual demands on quality control of both materials and processes. 

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