Applications in Drug Delivery

Inhalable drug delivery At present, there are many drugs that are applied through the nasal pathway (inhalable drug delivery [IDD]). Besides small molecules (such as hormones), even much larger molecules (such as insulin and other proteins) have been reported as useful IDD systems. However, they need to meet certain critical demands  

The particles (in the form of aerosols) need to be designed to achieve consistent delivery 

Surface-active substances, which are known to enhance penetration through the skin barrier, also needs to be added. These should, of course, not cause any irritation in the nose and other air pathways. Insulin is currently being marketed commercially for IDD. 

Chitosan is widely used for dental, buccal, gastrointestinal, colon-specific, and gene delivery applications due to its favorable biological properties. It is used in the form of tablets, gels etc. (Fig. 3). 

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Xylans from beech wood, corncobs, and the alkaline steeping liquor of the viscose process have been shown to be applicable as pharmaceutical auxiliaries [3]. Micro- and nanoparticles were prepared by a coacervation method from xylan isolated from corncobs [150]. The process is based on neutralization of an alkaline solution in the presence of surfactant, which was shown to influence both the particle size and morphology. They are aimed at applications in drug delivery systems. 

Ethylene vinyl acetate has also found major applications in drug delivery. These copolymers used in drug release normally contain 30-50 wt% of vinyl acetate. They have been commercialized by the Alza Corporation for the delivery of pilocarpine over a one-week period (Ocusert) and the delivery of progesterone for over one year in the form of an intrauterine device (Progestasert). Ethylene vinyl acetate has also been evaluated for the release of macromolecules such as proteins. The release of proteins form these polymers is by a porous diffusion and the pore structure can be used to control the rate of release (3). Similar nonbiodegradable polymers such as the polyurethanes, polyethylenes, polytetrafluoroethylene and poly(methyl methacrylate) have also been used to deliver a variety of different pharmaceutical agents usually as implants or removal devices. 

As noted in the patent for this system, pulsatile systems are expected to have numerous applications in drug delivery, including site-specific delivery in the GI tract and bid (twice-a-day) dosing of two pulsatile systems that simulates qid (four times a day) dosing of immediately available products. The latter concept is expected to have a particular advantage for those drugs that have high first-pass metabolism. 

Recent advances in nanotechnology have shown that self-assembled cage structures of nanometer dimensions can be used as constrained environments for the encapsulation of guest molecules with potential applications in drug delivery,... 

Gaucher G, Dufresne MH, Sant VP et al (2005) Block copolymer micelles preparation, characterization and application in drug delivery. J Control Release 109 169-188... 

The chemistry of polyanhydrides is by no means limited to the categories discussed in the preceding sections. A brief review of some of the additional chemistries that have recently been synthesized follows with a mention of their potential for application in drug delivery. 

Goldberg M, Langer R, Jia XQ (2007) Nanostructured materials for applications in drug delivery and tissue engineering. J Biomat Sci-Polym E 18 241-268. 

Gupta, P.K. and Haung, C.T. (1989). Albumin microspheres II. Applications in drug delivery. 

Some researchers see a bright future for dendrimers in many different industrial, medical, research, and consumer applications. One company that produces dendrimers lists applications in drug delivery systems, gene transfection, biotechnology, sensors for diagnostics and detection systems, carbon fiber coatings, microcontact printing, adhesion, molecular batteries, catalysis, separation systems, lasers, composites, and ultrathin films used in optics. 

Hydrogel micro- and nanoparticles composed of biopolymer matrixes have gained a lot of attention in recent years due to their application in drug delivery and tissue engineering [10,14,45 17], The biopolymers used for these purposes are nontoxic,... 

Drug encapsulation efficiency Active or remote loading [11] Stable liposome encapsulation of drugs at high drug-to-lipid ratios, Many applications in drug delivery... 

It is well known that liposomes have many applications in drug delivery. Initially, after the limitations of conventional liposomes were noticed, great effort was given... 

Avgoustakis, K. (2004), Pegylated poly(lactide) and poly(lactide-co-glycolide) nanoparticles Preparation, properties and possible applications in drug delivery, Curr. Drug Deliv., 1(4), 321-333. 

Tyle, P. Liquid crystals and their applications in drug delivery. In Controlled Release of Drugs Polymers and Aggregate Systems Rosoff, M., Ed. VCH Publishers New York, 1989 125-162. 

In addition to the equilibrium phase structures mentioned above, non-equilibrium surfactant phase structures exist thatare also finding applications in drug delivery. Vesicular forms of surfactants are generally formed by dispersing lamellar phases in an excess of water (or non-aqueous polar solvents such as ethylene glycol or dimethylformamide) or, in the case of reversed vesicles, in an excess of oil. With most surfactants, vesicles are non-equilibrium structures that will eventually re-equilibrate back into the lamellar phases from which they originated. Vesicles are structural analogs of liposomes (discussed later) they are approximately spherical structures and have the ability... 

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