Surgery – Means for introducing or removing material from body for... – Infrared – visible light – ultraviolet – x-ray or electrical...
Reexamination Certificate
1999-05-24
2003-04-08
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Infrared, visible light, ultraviolet, x-ray or electrical...
C604S291000, C604S113000
Reexamination Certificate
active
06546281
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for facilitating temperature controlled dermal drug delivery. Specifically, the present invention relates to a configuration and use of an integrated temperature control device and a dermal drug delivery system. More specifically, the present invention relates to the configuration and use of an integrated layer of transdermally delivered drug formulation and a controlled heat aided drug delivery patch (hereinafter CHADD patch). The transdermally delivered drug formulation provides a non-invasive method for delivery of a therapeutic agent. The CHADD patch provides temperature control and facilitates dermal drug absorption. The present invention provides the convenience of an integrated dermal drug formulation and a CHADD patch while maintaining the stability of the CHADD patch and the drug formulation.
2. Relevant Technology
The dermal administration of pharmaceutically active compounds involves the direct application of pharmaceutically active formulations to the skin, wherein the skin absorbs a portion of the pharmaceutically active compound which is then taken up by the skin, tissues under the skin and the bloodstream. Such administration has long been known in the practice of medicine and continues to be an important technique in the delivery of pharmaceutically active compounds. For example, U.S. Pat. No. 4,286,592 issued Sep. 1, 1981, to Chandra Sicaran shows a bandage for administering drugs to a user's skin consisting of an impermeable backing layer, a drug reservoir layer composed of a drug and a carrier, and a contact adhesive layer by which the bandage is affixed to the skin.
For some drugs such dermal administration offers many important advantages over other delivery techniques, such as injection, oral tablets, and capsules. These advantages include being non-invasive, avoiding first pass metabolism of the drug in the liver when the drug is taken orally and absorbed through the gastrointestinal tract, and in some instances, avoiding undesired high peaks and low valleys of concentration of pharmaceutically active compounds in the patient's bloodstream. Other possible advantages include: avoidance of a harsh environment in the stomach, reduced total dosage, reduced cost in some instances, and improved compliance with prescribed use.
The term “dermal drug delivery system” or “DDDS”, as used herein, is defined as an article, apparatus, or method for administering pharmaceutically active compound(s) for delivery into the skin, the regional tissues under the skin, the systemic circulation, or other targeting site(s) in a human body via skin permeation. The term “DDDS” in this application, unless otherwise specified, only refers to those systems in which the main driving force for drug permeation is the drug concentration gradient (passive permeant).
The term “skin,” as used herein, is defined to include stratum corneum covered skin and mucosal membranes.
The term “drug,” as used herein, is defined to include any pharmaceutically active compound, including but not limited to, compounds that treat diseases, injuries, undesirable symptoms, and improve or maintain health.
In DDDSs, a drug(s) is usually contained in a formulation, such as a hydro-alcohol gel, and may include a rate limiting membrane between the formulation and skin for minimizing the variation in the permeation of the drug. When a DDDS is applied to skin, the drug begins to transport out of the formulation, and transport across the rate limiting membrane (if present). The drug then enters the skin, enters blood vessels and tissues under the skin, and is taken into the systemic circulation of the body by the blood. At least some DDDSs have certain amounts of pharmaceutically active compound in or on the skin side of the rate limiting membrane (if present) prior to use. In those DDDSs, that portion of the drug on the skin side of the rate limiting membrane will enter the skin without passing through the rate limiting membrane. For many drugs, a significant portion of the dermally absorbed drug is stored in the skin and/or tissues under the skin (hereinafter referred as “depot sites”) before being gradually taken into the systemic circulation (hereinafter referred to as “depot effect”). This depot effect is believed to be at least partially responsible for the delayed appearance of the drug in the systemic circulation after the application of some DDDSs and for continued delivery of the drug into the systemic circulation after the removal of some DDDSs from the skin.
After placing a DDDS on the skin, the drug concentration in the targeted tissue or blood typically remains at or near zero for a period of time, before starting to gradually increase and reach a concentration deemed to be medicinally beneficial, called the “therapeutic level” (the time it takes to reach the therapeutic level is referred to hereinafter as the “onset time”). Ideally, the concentration of the drug in the targeted tissue or blood should plateau (i.e., reach a substantially steady state) at a level slightly higher than the therapeutic level and should remain there for extended period of time. For a given person and a given DDDS, the “concentration of the drug in the targeted tissue or bloodstream vs. time” relationship usually cannot be altered under normal application conditions.
The onset time and the delivery rate of the drug into the targeted area(s) of the body for a typical DDDS are usually determined by several factors, including: the rate of release of the drug from the formulation, the permeability of the drug across the rate limiting membrane (if a rate limiting membrane is utilized), the permeability of the drug across the skin (especially the stratum corneum layer), drug storage in and release from the depot sites, the permeability of the walls of the blood vessels, and the circulation of blood and other body fluid in the tissues (including the skin) under and around the DDDS. Although these primary factors affecting onset time and delivery rate are known, no existing DDDS is designed to have alterable delivery rate in the course of the application of the drug and therefore no existing DDDS is able to provide for example, an increased concentration of a pharmaceutically active compound in a patient's bloodstream for a short period of time (a narrow peak) in the course of the application of a DDDS, when it is desirable to do so.
While a DDDS works well in many aspects, current dermal drug delivery technology has some serious limitations, including: 1) the onset time is undesirably long for many DDDSs; 2) the rate that the drug is taken into the systemic circulation or the targeted area(s) of the body cannot be easily varied once the DDDS is applied onto the skin and, when the steady state delivery rate is achieved, it cannot be easily changed; and 3) the skin permeability is so low that many drugs are excluded from dermal delivery because the amount of drug delivered is not high enough to reach a therapeutic level. In addition, temperature variations in the skin and the DDDS are believed to contribute to the variation of dermal absorption of drugs.
It is known that elevated temperature can increase the absorption of drugs through the skin. U.S. Pat. No. 4,898,592 issued Feb. 6, 1990 to Latzke et al., relates to a device for the application of heated transdermally absorbable active substances which includes a carrier impregnated with a transdermally absorbable active substance and a support. The support is a laminate made up of one or more polymeric layers and optionally includes a heat conductive element. This heat conductive element is used for distribution of the patient's body heat such that absorption of the active substance is enhanced. U.S. Pat. No. 4,230,105, issued Oct. 28, 1980 to Harwood, discloses a bandage with a drug and a heat-generating substance, preferably intermixed, to enhance the rate of absorption of the drug by a user's skin. Separate drug and heat-generating substance l
Hull Wade A.
Rigby Larry
Zhang Hao
Zhang Jie
Kennedy Sharon
Kirton & McConkie
Krieger Michael F.
Zars, Inc.
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