Frontiers of Engineering Reports on Leading-Edge Engineering from the 2008 Symposium (2009) / Chapter Skim
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Recent Developments in Needle-Free Drug Delivery--Samir Mitragotri
Recent Developments in Needle-Free Drug Delivery--Samir Mitragotri
Pages 5-16
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From page 5... ...
. The ability of drugs to reach target tissues from the point of administration via pills or injections is limited by the body's multiple barriers, including enzymatic degradation in the stomach, absorption across the intestinal epithelium, hepatic clearance, and accumulation in nontargeted tissues.
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grown in response to these challenges and is now a significant component of the overall drug development process. In the past several decades, tremendous progress has been made toward the development of safe, effective, and convenient means of drug administration.
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This article provides a brief review of past efforts, a description of the current status, and prospects for the future, with an emphasis on transdermal and oral drug delivery. Transdermal Drug Delivery Skin, the largest human organ, provides a painless, compliant interface for systemic drug administration (Zaffaroni, 1991)
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From page 8... ...
Opening the transdermal route to large hydrophilic drugs, a major challenge in the field of transdermal drug delivery, will require the development of technologies that enable the controlled, reproducible transdermal delivery of macromolecular drugs. Passive Methods Technologies that facilitate transdermal drug delivery can work either passively or actively, depending on whether an external source of energy is used to facilitate skin permeation (Figure 2)
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From page 9... ...
However, so far, the rational design of combinations of enhancers has been limited by the lack of information on interactions between individual chemical enhancers and the stratum corneum. The number of randomly generated formulations for binary mixtures is in the millions, and the number for higher order formulations (for example, ternary or quaternary mixtures)
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In contrast, jet injectors deliver a high-velocity liquid jet stream into the skin, delivering drugs into various skin layers, depending on the jet parameters (Mitragotri, 2006)
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Drugs delivered orally are typically absorbed across the intestinal epithelium into the bloodstream via two mechanisms. The transcellular route involves the transport of drugs through the cell membrane to cross the barrier, either by partitioning of the drug into cell membranes or through the generation of small pores in the outer cell membrane, which allows entry into the cell.
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From page 12... ...
. These methods include enzyme inhibitors, permeation enhancers, mucoadhesive polymers, chemical modification of drugs, targeted delivery, and encapsulation.
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This kind of localization results in a high concentration gradient of the drug across the epithelial barrier, which improves drug bioavailability. In addition, a strong adhesion force prolongs the residence time of the dosage at the site of drug absorption, which reduces the dosing frequency and, in turn, increases patient compliance.
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2004. Transdermal drug delivery with a pressure wave.
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2006. Low-frequency sonophoresis: ultrastructural basis for stratum corneum permeability assessed using quantum dots.
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2008. Mechanistic analysis of chemical permeation enhancers for oral drug delivery.
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