Controlled delivery of therapeutics

Membrane-reservoir systems based on solution-diffusion mechanism have been utilized in different forms for the controlled delivery of therapeutic agents. These systems including membrane devices, microcapsules, liposomes, and hollow fibres have been applied to a number of areas ranging from birth control, transdermal delivery, to cancer therapy. Various polymeric materials including silicone rubber, ethylene vinylacetate copolymers, polyurethanes, and hydrogels have been employed in the fabrication of such membrane-reservoir systems (13). 

PROGRESS IN DESIGN OF BIODEGRADABLE POLYMER-BASED MICROSPHERES FOR PARENTERAL CONTROLLED DELIVERY OF THERAPEUTIC PEPTIDE/PROTEIN... 

Shunmugaperumal Tamilvanan, University of Antwerp, Antwerp, Belgium, Progress in Design of Biodegradable Polymer-Based Microspheres for Parenteral Controlled Delivery of Therapeutic Peptide/Protein Oil-in-Water Nanosized Emulsions Medical Applications... 

Kost, J. Ultrasound for controlled delivery of therapeutics. Clin. Mater. 1993, 13 (1 ), 155-161. 

Kost, J., and hanger, R. (1992) Responsive polymer systems for controlled delivery of therapeutics. Trends Biotech-nol, 10, 127-131. 

Controlled and sustained drug delivery has recently begun to make an impression in the area of treatment of dental diseases. Many researchers have demonstrated that controlled delivery of antimicrobial agents, such as chlorhexidine [128-130], ofloxacin [131-133], and metronidazole [134], can effectively treat and prevent periodontitis. The incidence of dental caries and formation of plaque can also be reduced by controlled delivery of fluoride [135,136]. Delivery systems used are film-forming solutions [129,130], polymeric inserts [132], implants, and patches. Since dental disease is usually chronic, sustained release of therapeutic agents in the oral cavity would obviously be desirable. 

Mehvar R (2000) Dextrans for targeted and sustained delivery of therapeutic and imaging agents. J Control Release 69 1-25... 

Recent development in polymeric delivery systems for the controlled release of therapeutic agents has demonstrated that these systems not only can improve drug stability both in vitro and in vivo by protecting labile drugs from harmful conditions in the body, but also can increase residence time at the application site and enhance the activity duration of short half-life drugs. Therefore, compounds which otherwise would have to be discarded due to stability and bioavailability problems may be rendered useful through a proper choice of polymeric delivery system. 

Figure 3. An expanded diagram to illustrate the concept of enhancing the skin permeation of drugs by first releasing one or more enhancers to skin surface to modify the permeability characteristics of stratum corneum prior to the controlled delivery of a therapeutically active drug.

The selective activation of compounds with potential therapeutic effects and the controlled delivery of bioactive molecules triggered by light are topics of intensely growing interest (6,197-200). Besides the search for light-sensitive prodrugs activated by photochemical cleavage, isomerization or photoredox processes (201-203), especially the release of small molecules such as NO, CO, CS2, and H2S, have attracted a lot of interest in the past years (204-208). 

Chien YW, Lelawongs P, Siddiqui O, and Shi W. Facilitated transdermal delivery of therapeutic peptides and proteins by iontophoretic delivery devices. J. Control. Rel. 1990 13 263-278. 

Machluf, M. Orsola, A. Atala, A. Controlled release of therapeutic agents slow delivery and cell encapsulation. World J. Urol. 2000, 18 (1), 80-83. 

Given the limitations imposed on transdermal systemic drug delivery by the barrier properties of the stratum corneum, new technologies have attempted to completely bypass this obstacle by either the creation of a physical conduit (microneedles) or direct powder delivery via compressed gas. The Alza Corporation technology (Macroflux ) comprises a patch system that contains a microprojection array designed to create superficial microchannels across the stratum corneum.When used in conjunction with their electrotransport system, the Macroflux system provides controlled in vivo delivery of therapeutic doses of... 

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