Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the transdermal delivery of active agents
underneath
the surface of the skin for treating lesions, diseased tissue or damaged skin.
More
specifically, it relates to a portable device for the iontophoretic delivery
of active agents
into the epidermis and dermis so as to obtain efficient penetration at the
delivery site in a
targeted manner.
2. Prior Art
Iontophoresis has been employed for several decades as a means for applying
medication
through a patient's skin. The application of an electric field to the skin is
known to greatly
enhance the transport of various ionic agents especially through the most
external layers
of the skin, i.e., stratum corneum and the epidermis, to reach ultimately
small capillary
vessels located in the dermis. Based on this principle, iontophoretic
transdermal delivery
techniques have been proposed as a substitute to hypodermic injection for many
medicaments, thereby eliminating the concomitant problems of trauma, pain and
risk of
infection to the patient.
In iontophoresis, the application of an electrical field drives charged ions
through dermal
layers into a target tissue. This technique enables the non-invasive,
controlled
administration of therapeutic agents for either local or systemic action.
Recently, a device
has been launched for administering lidocaine for local anesthesia in infants
prior to
superficial dermatological procedures (LidoSiteTM, Vyteris, Inc., Fair Lawn,
NJ) (Kalia et
al., 2004). This device, in which the positively-charged lidocaine is
transported from the
anodal compartment into the skin, results in local anaesthesia within 10
minutes - within
which period the drug reaches the nerves located in the dermis and epidermis.
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For dermatological applications, one targets tissues adjacent to the delivery
site in order
to effect a localized treatment. So far, the technique of iontophoresis has
been used only
rarely for the topical administration of agents to treat various
dermatological conditions.
One may explain that the use of iontophoretic patches usually fitted with an
adhesive to
hold the patch in place is not appropriate for treating various skin
conditions, even more
so in the case of apparent skin lesions requiring the local administration of
medicated
agents.
US Patent 5,676,648 describes a device for administering anti-virals for
example to
localized lesions in the face: the apparatus, designed to be hand-held,
employs a
detachable non-reusable medicament-containing applicator electrode which is
adapted to
attach to a base assembly. The second electrode, also called the counter-
electrode, is a
circumferential tactile band made of conductive material located on the base
assembly.
The electrical circuit is completed by the electrical connection between the
skin of the
user's hand and the device, implying the passage of an electrical current
through the arm
and other parts of the body forming a path to the site of application. US
Patents 6,148,231
and 6,735,470 provide additional improvements of that invention in that the
counter-
electrode is in the form of a thimble fitted to the user's finger; the user
can apply the
medication loaded electrode for the desired period of time by exerting
pressure on the
lesion with the finger covered with a complicated device which appears very
uncomfortable for the user.
The present invention consists of a compact cylindrical device fitted with a
disposable tip
containing the active ingredient. The device can be easily maneuvered with one
hand and
its tip precisely applied to the treatment site without recourse to the user's
arm and body
to conduct electricity for the iontophoretic process. The compact design
combined with
the establishment of an electrical circuit loop limited to the treatment site
enables an
efficient treatment in a short period of time. Furthermore, the device can be
used by a
health professional to treat areas of the skin not readily accessible to the
user.
SUMMARY OF THE INVENTION
The present invention discloses a portable iontophoretic device made up of two
parts: a
reusable cylindrical holder containing two contact pads, the power supply and
the
electronic controller required to create the electrical field in the skin and
a disposable tip
assembly made up of two compartments, one for each electrode.
In the disposable tip assembly (See Drawing entitled "DISPOSABLE APPLICATOR
A"), the
central compartment of cylindrical shape contains the active agent lodged
within a porous
polymeric matrix or within a firm hydrogel allowing the flow of current.
Delivery of the
active agent is obtained by applying the distal end of the disposable tip
assembly to the
area of skin to be treated and activating the electronic controller. The
peripheral
compartment, isolated from the central compartment, contains a certain amount
of the
counter-ion also in a porous matrix or in a hydrogel and serves to complete
the circuit
loop in the skin tissue touching the distal end of the disposable tip
assembly. In this
invention, the two compartments are so designed to offer a compact
configuration
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allowing the application of the device specifically to the treatment site
without recourse
to the user's finger, arm and body to conduct the current necessary to
establish the current
loop.
If the active ingredient is positively charged at physiological pH, the
central electrode
becomes the anode and the peripheral electrode the cathode. The peripheral
compartment
contains a negative counter-ion. If the active ingredient is negative, the
central
compartment becomes the cathode, the peripheral compartment contains a
positive
counter-ion and the peripheral electrode becomes the anode.
The cylindrical holder is so designed to present at its upper extremity two
axi-
symmetrical planar contact pads made of a good metal conductor (See Drawing
entitled
"REUSABLE CONTROLLER A"). The outer surface of these two contact pads have the
same
dimensions as the external surface of the two compartments on the proximal end
of the
disposable tip assembly. The two contact pads are separated by a gap allowing
the
insertion of a cylindrical wall made of non-conducting material around the
central
electrode when the disposable tip assembly is fitted to the top of the
cylindrical holder.
This cylindrical wall contributes to eliminate short circuiting between the
two electrodes
and to position precisely the disposable tip assembly onto the upper extremity
of the
cylindrical holder.
In one embodiment of this invention (See Drawing entitled "DISPOSABLE
APPLICATOR
B"), the central compartment is so designed to protrude from the distal end of
the
disposable assembly tip so that this compartment loaded with the drug exerts a
somewhat
larger pressure onto the skin, thereby facilitating the establishment of a
three dimensional
electrical field at the treatment site.
In another embodiment of this invention, the peripheral compartment can be so
designed
to protrude from the distal end of the disposable tip assembly so as to
increase its surface
area in contact with the external skin layer and to exert a light pressure on
it, thereby
facilitating the establishment of a three-dimensional electrical field at the
treatment site.
One novel aspect of this invention consists of making the peripheral
compartment out of
a porous polymeric matrix resilient enough to effect pressure around the skin
area to be
treated in order to obtain a good electrical contact between the skin and the
cathode, and
yet permeable enough to permit the flow of counterions towards the skin.
This particular invention allows the delivery of the active agent by exerting
a gentle
pressure with the portable iontophoretic device to a lozalized portion of the
skin. The
desired pharmacological action is obtained by combining the appropriate
quantity of
active agent in the central compartment and by selecting the required current
and voltage
condition for the electrical controller located in the cylindrical holder. In
optimal
conditions, the delivery is efficient enough to take place in a reasonably
short period of
time during which the user applies the iontophoretic device to the portion of
the skin to
be treated.
