Electricity: measuring and testing – Determining nonelectric properties by measuring electric...
Patent
1996-10-31
1999-03-30
Brown, Glenn W.
Electricity: measuring and testing
Determining nonelectric properties by measuring electric...
324439, 324693, 324717, G01N 2704
Patent
active
058893962
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and to a device for measuring the quantity of an active principle contained in a reservoir, as well as to a reservoir designed to allow such a measurement. More particularly, the invention relates to such a method, device and reservoir employed in the context of transdermal delivery of medicinal products assisted by iontophoresis.
FIG. 2 of the attached drawing diagrammatically represents means which can be used for carrying out such delivery. These means essentially comprise, in a known manner, a reservoir 1 comprising a layer 2 of a material, such as a hydratable polymer or "hydrogel", impregnated with a solution of the active principle, this layer 2 being designed to be placed in contact with the skin 3 of a patient. The active principle is present in the solution in an ionized form, so that its passage through the skin of the patient can be assisted by iontophoresis. In order to do this, the reservoir is connected to an electronic module 4 comprising means 5 for generating and means 6 for controlling a so-called "therapeutic" current which passes through the patient between an electrode 7, which may form part of the reservoir 1, and an adjacent electrode 8, so as to establish current lines 9 under the skin of the patient. The ions of the active principle flow down these current lines, starting from the reservoir 1 then crossing the dermis and passing into the underlying capillary vessels. The control means 6, for example a microcontroller, control the amplitude and the waveform of the applied current so that the quantity of active principle passing into the blood is modulated in time according to a precise delivery program, established on the basis of pharmacological considerations.
This program should thus respect the minimum and maximum values of the doses of active principle applied per unit time. An overdose may be highly dangerous for the safety of the patient, whereas an insufficient dose does not allow the desired pharmacological activity to be ensured. It should be pointed out, in this regard, that the quantities of active principle to be delivered do, of course, vary from one active principle to another, and that the delivery program should be capable of adapting to the variations in the permeability of the skin, from one patient to another.
It will be understood that, in order to ensure that the program is followed, it is then necessary for the control means to be fed back with a measurement of the quantity of active principle actually delivered to the patient, all along the delivery time of said active principle.
For this purpose, a method and an apparatus for dosage of the quantities of active principle delivered, operating by integration over time of the "therapeutic" current passing through the patient between the electrode 7 and the electrode 8 are proposed in European Patent Application No. 0,277,314 in the name of R. TAPPER. This method is burdened with the drawback that the current passing between the two electrodes is not necessarily representative of the number of ions of the active principle which have left the reservoir and passed into the blood of the patient. Iontophoresis does in fact have an efficiency which is less than one, and in addition, can vary from one patient to another, and from one condition of the skin of the patient to another, this condition varying progressively during the delivery of the medicinal product, which may commonly last several hours.
Another solution which is theoretically envisageable, but difficult, might consist in in vivo dosage of the quantity of active principle present in the blood of the patient.
The object of the present invention is to provide a method and a device for measuring the quantity of an active principle contained in a reservoir, which does not have the abovementioned drawbacks of the prior art.
A further object of the invention is to provide an active principle reservoir which is suitable for implementing the method according to the invention.
The objects of the invention, as well as othe
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Liotard Anne
Millot Philippe
Brown Glenn W.
Laboratoires d'Hygiene et de Dietetique (L.H.D.)
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