Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1998-12-09
2001-11-27
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S449000, C604S046000, C604S047000, C604S048000, C604S041000, C604S058000, C604S117000, C604S181000, C604S290000, C604S890100
Reexamination Certificate
active
06322808
ABSTRACT:
TECHNICAL FIELD
The present invention relates to transdermal agent delivery and sampling. More particularly, this invention relates to the transdermal delivery of agents, such as peptides and proteins, through the skin, as well as the transdermal sampling of agents from the body, such as glucose, other body analytes and substances of abuse, such as alcohol and illicit drugs.
BACKGROUND ART
Interest in the percutaneous or transdermal delivery of peptides and proteins to the human body continues to grow with the increasing number of medically useful peptides and proteins becoming available in large quantities and pure form. The transdermal delivery of peptides and proteins still faces significant problems. In many instances, the rate of delivery or flux of polypeptides through the skin is insufficient to produce a desired therapeutic effect due to their large size/molecular weight and the resulting inability to pass through natural pathways (pores, hair follicles, etc.) through skin. In addition, polypeptides and proteins are easily degradable during penetration of the skin, prior to reaching target cells. Likewise, the passive flux of water soluble small molecules such as salts is limited.
One method of increasing the transdermal delivery of agents relies on the application of an electric current across the body surface or on “electrotransport”. “Electrotransport” refers generally to the passage of a beneficial agent, e.g., a drug or drug precursor, through a body surface such as skin, mucous membranes, nails, and the like. The transport of the agent is induced or enhanced by the application of an electrical potential, which results in the application of electric current, which delivers or enhances delivery of the agent. The electrotransport of agents through a body surface may be attained in various manners. One widely used electrotransport process, iontophoresis, involves the electrically induced transport of charged ions. Electroosmosis, another type of electrotransport process, involves the movement of a solvent with the agent through a membrane under the influence of an electric field. Electroporation, still another type of electrotransport, involves the passage of an agent through pores formed by applying a high voltage electrical pulse to a membrane. In many instances, more than one of these processes may be occurring simultaneously to different extents. Accordingly, the term “electrotransport” is given herein its broadest possible interpretation, to include the electrically induced or enhanced transport of at least one charged or uncharged agent, or mixtures thereof, regardless of the specific mechanism(s) by which the agent is actually being transported. Electrotransport delivery generally increases agent delivery, particularly large molecular weight species (e.g., polypeptides) delivery rates, relative to passive or non-electrically assisted transdermal delivery. However, further increases in transdermal delivery rates and reductions in polypeptide degradation during transdermal delivery are highly desirable.
One method of increasing the agent transdermal delivery rate involves pre-treating the skin with, or co-delivering with the beneficial agent, a skin permeation enhancer. The term “permeation enhancer” is broadly used herein to describe a substance which, when applied to a body surface through which the agent is delivered, enhances its flux therethrough. The mechanism may involve a reduction of the electrical resistance of the body surface to the passage of the agent therethrough, an increase in the permselectivity and/or permeability of the body surface, the creation of hydrophilic pathways through the body surface, and/or a reduction in the degradation of the agent (e.g., degradation by skin enzymes) during electrotransport.
There have been many attempts to mechanically disrupt the skin in order to enhance transdermal flux, such as, U.S. Pat. Nos. 3,814,097 issued to Ganderton et al., 5,279,544 issued to Gross et al., 5,250,023 issued to Lee et al., 3,964,482 issued to Gerstel et al., U.S. Pat. No. Re 25,637 issued to Kravitz et al. and PCT application WO 96/37155. These devices typically utilize tubular or cylindrical structures generally, although Gerstel does disclose the use of other shapes, to pierce the outer layer of the skin. The piercing elements disclosed in these references generally extend perpendicular from a thin flat member, such as a pad or metal sheet. The flexible nature of the flat member and the tubular shape of the piercing elements result in a variety of short-comings, such as manufacturing difficulties, flexing of the flat member when pressure is applied to the top of the device, uneven penetration of the skin, poor puncturing of the skin resulting in low transdermal flux and, for electrotransport, increased irritation due to concentrating the drug flux through fewer pathways.
DESCRIPTION OF THE INVENTION
The present invention provides a device suitable for increasing transdermal flux. The device has microprotrusions which consistently and reliably penetrate a body surface (e.g., skin) to enhance agent delivery or sampling. The device of the present invention can be easily manufactured in high volumes and at low cost. The device of the present invention can penetrate the stratum corneum of skin with a plurality of microprotrusions to form pathways through which a substance such as a drug can be introduced (i.e., delivery) or a substance such as a body analyte can be withdrawn (i.e., sampling). A principal advantage of the present invention is that the device ensures uniform penetration (i.e., generating the same size and depth pathways) by the microprotrusions across the device. Furthermore, the present invention reproducibly provides uniformity in penetration from patient to patient.
In one aspect, the invention comprises a rigid structure which contacts and extends across a flexible device having a plurality of microprotrusions for piercing the skin. The rigid structure transmits force applied to the top of the structure substantially evenly across the flexible device and thus transmits uniform displacement of the microprotrusions. This is accomplished with substantially less dissipation of the application force in the compliant elements of the flexible device having the microprotrusions. The rigid structure provides assured transmittance of an externally applied load to the microprotrusions for easier, complete and reproducible skin penetration. The improved penetration of the skin by the microprotrusions because of the rigid structure is particularly beneficial in producing increased flux. The evenly distributed displacement of the microprotrusions provides nearly complete penetration by all of the microprotrusions so as to produce a substantial number of agent pathways and electrical continuity (if electrotransport is used) with the skin for continued and reproducible agent flux through the skin.
In one aspect of the invention, the flexible skin piercing device comprises a relatively thin flexible sheet which in use is adapted to be placed in substantially parallel relation with the body surface to be pierced. The sheet has a plurality of openings therethrough, which allow the agent to pass between a reservoir associated with the sheet (and typically positioned on the body distal surface of the sheet) and the holes pierced in the body surface by the microprotrusions. The sheet also has a plurality of microprotrusions (also referred to as micro-blades) extending approximately perpendicularly from a body proximal side of the sheet. In this aspect of the invention, a rigid support structure contacts and extends across the sheet in order to impart added structural rigidity thereto and to more evenly distribute any force applied to the device for purposes of more uniformly displacing the microprotrusions into (i.e., to pierce) the body surface. Optionally, though preferably, the rigid structure forms a void for an agent reservoir. The reservoir can be filled with an agent containing/sampling reservoir.
In a second aspect of the invention,
Daddona Peter E.
Kim Hyunok Lynn
Trautman Joseph Creagan
Wong Patrick S.-L.
Zuck Michael G.
ALZA Corporation
Bates Owen J.
Dodson Shelley A.
Miller D. Byron
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