AU2007202273B2

AU2007202273B2 - Transdermal therapeutic system containing fentanyl or related substance

Info

Publication number: AU2007202273B2
Application number: AU2007202273A
Authority: AU
Inventors: Thomas Hille; Walter Muller
Original assignee: LTS Lohmann Therapie Systeme AG
Current assignee: LTS Lohmann Therapie Systeme AG
Priority date: 2001-08-24
Filing date: 2007-05-21
Publication date: 2009-11-05
Anticipated expiration: 2022-07-10
Also published as: AU2007202273A1

Description

Pool Section 29 Regulation 3.2(2) AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Transdermal therapeutic system containing fentanyl or related substances The following statement is a full description of this invention, including the best method of performing it known to us: Transdermal therapeutic system containing fentanyl or related substances Description 5 Fentanyl and fentanyl-analogous substances such as sulfentanyl, carfentanyl, lofentanyl and alfentanyl are extremely efficacious analgesics. The requirement for only a low dose and their physicochemical properties 10 such as the n-octanol/water partition coefficient, melting point and the molecular weight make possible the transdermal administration of these substances in an efficacious amount and their pharmacokinetic properties such as the rapid metabolization and the 15 relatively narrow therapeutic index make transdermal administration desirable. In fact, a TTS containing fentanyl as active compound has been on the market for some years. This system is a 20 "reservoir system". A reservoir system is understood here as meaning a system which contains the active compound in a liquid or gelatinous preparation in a sachet formed from an impermeable film, which serves as a back layer, and an active compound-permeable 25 membrane, the membrane additionally being provided with an adhesive layer for fixing the system to the skin. In this specific case, fentanyl is dissolved in a mixture of ethanol and water. Further details of this system can be taken from US patent specification 4,588,580 or 30 DE-C 35 26 339, which both contain a detailed description. Reservoir systems, however, have the disadvantage that in the case of a leak in the reservoir sachet the 35 active compound-containing reservoir filling comes in contact with the skin over a wide area and the active compound is absorbed in excessively high doses. This is very dangerous, especially in the case of fentanyl and 2 its derivatives, since an overdose very rapidly leads to respiratory depression and therefore fatal incidents. A number of such fatal or near-fatal incidents are described in Clinical Pharmacokinet. 2000, 38(1), 59-89. The object of this invention was now to make available a transdermal 5 therapeutic system containing fentanyl or fentanyl analogs, which offers the user increased safety against an inadvertent absorption of overdoses. This is possible according to the invention in that, instead of the reservoir system, a matrix system is employed in which the active compound is incorporated directly into a self-adhesive polyacrylate and thus, even in the case 10 of damage to the system, cannot come into contact with the skin over a greater area than afforded by the TTS. SUMMARY OF THE INVENTION According to the invention, there is provided a transdermal therapeutic system (TTS) comprising: 15 a) an active compound-impermeable backing layer; b) at least one matrix layer based on polyacrylate and comprising fentanyl or a fentanyl-analogous active compound selected from the group consisting of sulfentanyl, carfentanyl, lofentanyl and alfentanyl; and c) a protective film to be removed before use, characterized in that the 20 polyacrylate is self-adhesive, free of carboxyl groups, is synthesized only from monomeric esters of alcohols comprising 1 to 8 C atoms, the alcohols having optionally a hydroxyl group, and of acrylic and/or methacrylic acid and, if appropriate, vinyl acetate in an amount of up to 50 percent by weight, and has a saturation solubility for said fentanyl or fentanyl-analgous active compound of 25 between 3 and 20 percent by weight, and in that the at least one matrix layer contains at least 5 percent by weight of the incorporated fentanyl or fentanyl analogous active compound, 80 percent by weight thereof being in molecularly dispersed, dissolved form. In a further aspect of the invention there is provided a transdermal 30 therapeutic system (TTS) comprising of: a) an active compound-impermeable backing layer; 2a b) at least one matrix layer based on polyacrylate and comprising a fentanyl-analogous active compound selected from the group consisting of sulfentanyl, carfentanyl, lofentanyl and alfentanyl; and c) a protective film to be removed before use, wherein the polyacrylate 5 is self-adhesive and free of carboxyl groups, has a saturation solubility for the active compound of between 3 and 20 percent by weight, and in that the at least one active compound-containing layer contains at least 80 percent by weight of the incorporated active compound in molecularly disperse dissolved form. In such a system, the active compound is generally completely, but to at 10 least 80%, dissolved in molecularly dispersed form in this polymer, the saturation solubility of the active compound in the polymer being between 3 and 20% by weight. Furthermore, it has surprisingly been shown that when using polyacrylate adhesives for the production of TTS containing fentanyl and its analogs, only adhesives without free carboxyl groups are suitable. 15 DETAILED DESCRIPTION OF THE INVENTION The matrix systems according to the invention, in the simplest case consist of a backing layer, which is impermeable to the active compound, a self-adhesive active compound-containing layer and a protective layer to be removed before use. In complicated embodiments of such systems, there is additionally also 20 added a membrane controlling the release of active compound, which is normally further provided with an adhesive layer for fixing the system to the skin. The active compound-containing layers of such a matrix system according to this invention consist of -3 polyacrylates. Since free functional groups increase the saturation solubility of fentanyl and its derivatives in polyacrylate adhesives above the preferred range, the polyacrylate adhesives which are 5 best suited are those which have no free functional groups and are only prepared from esters of acrylic and/or methaycrylic acid and optionally other vinyl compounds without free functional groups such as vinyl acetate. However, in the synthesis of the adhesive, 10 monomers having free hydroxyl groups such as 2 hydroxyethyl acrylate or 2-hydroxyethyl methacrylate can be tolerated up to a content of 20% by weight. Polyacrylates are prepared by free-radical polymerization using acrylic and/or methacrylic acid 15 derivatives. Such derivatives are, for example, esters. By way of example of such derivatives, acrylic and methacrylic acid derivatives may be mentioned, in particular esters of alcohols having 1 to 8 C atoms, which optionally contain one hydroxyl group, such as 20 2-ethylhexyl acrylate, n-octyl acrylate, propyl acrylate, n- or isobutyl acrylate, 2-hydroxyethyl acrylate and dimethylaminoethyl acrylate or the corresponding methacrylates. Additionally, other polymerizable vinyl compounds without free functional 25 groups such as, for example, vinyl acetate can also be used, e.g. in amounts of up to 50% by weight. The polymers thus prepared are also described as random copolymers, as solely the quantitative distribution of the monomers employed and chance decide the composition 30 of the polymer chains. If the polymers contain free hydroxyl groups, the possibility exists of additionally crosslinking the polymer chains by polyvalent cations such as Al' or 35 Ti'* or reactive substances such as melamine. Use is made of this possibility in order to increase the molecular weight and thus to improve the cohesion of the polymers. The possibility of the crosslinkage of polyacrylates, in particular of polyacrylate adhesives, - 4 is particularly valuable if the plasticizing action of the active compound dissolved in the polymers or the plasticizing action of other auxiliaries has to be compensated. The adhesive is usually used in the form 5 of a solution. Solvents used are, for example, ethyl acetate, hexane or heptane, ethanol or their mixtures. These are removed during the preparation of the TTS. Table 1 shows the results of permeation studies which 10 have been obtained using an adhesive with and an adhesive without free carboxyl groups (but without hydroxyl groups) . In both adhesives, the active compound was incorporated in a concentration of 5 percent by weight. The permeation study was carried 15 out by means of the Franz diffusion cells known to the person skilled in the art and using human skin. Table 1: Results of permeation studies using adhesives with and without free carboxyl groups 20 Cumulated amount of permeated active compound [pg/cm 2 Mean value of n = 3 * Formulation 4 h 8 h 24 h 48 h 72 h 1 0.00 0.00 0.44 1.71 3.51 2 0.0 0.2 4.0 14.7 28.24 * skin used: female lower abdominal skin Formulation 1: polyacrylate adhesive with 4.8% by weight of free carboxyl groups 25 Formulation 2: neutral polyacrylate adhesive without free carboxyl groups but with 5.2% by weight of free hydroxyl groups The results show that a neutral adhesive without free 30 carboxyl groups is markedly superior to a carboxyl group-containing adhesive with respect to the permeation rates achievable.

-5 An important characteristic of each active compound containing polymer in TTS technology is the saturation solubility of the chosen polymer for the respective 5 active compound. This parameter is important because the thermodynamic activity of the active compound in the matrix does not depend on the absolute amount of active compound dissolved, but rather on the ratio of the actual concentration to the saturation 10 concentration. Since the active compound on application of the TTS to the skin must disperse in the skin and in the process bring into line not concentrations, but activities, it is important for achieving a permeation rate which is as high as possible to choose as high as 15 possible a thermodynamic activity of the active compound in the TTS. This means that the solubility of the active compound in the active compound-containing parts of the TTS must not be too high, since otherwise the active compound concentration in the TTS must be 20 quite high in order to achieve an adequately high thermodynamic activity. This is unadvantageous if the active compound disadvantageously influences the physical properties of the active compound-containing parts of the system in the high concentration and/or 25 the active compound is very expensive. In the case of fentanyl, both reasons are true, it additionally still having to be taken into consideration that fentanyl and its derivatives belong to the narcotics and for this reason alone it is therefore desirable to incorporate 30 as little active compound in the TTS as possible and/or to make the utilization of active compound, i.e. the ratio of active compound released during the wearing time of the TTS to the content of the unworn TTS, as large as possible. 35 From this point of view, the saturation solubility of the active compound-containing layers for a three-day TTS should not be below 3 percent by weight and not above 20 percent by weight. At higher saturation - 6 solubilities, even with a high specific permeation rate, the utilization of active compound is too poor, and the TTS is not readily marketable for commercial reasons because of the expensive active compound. 5 Preferably, for these reasons the saturation solubility is between 4 and 12 and particularly preferably between 5 and 10, percent by weight. The saturation solubility of fentanyl and its analogs 10 can additionally be reduced by the addition of substances which do not have good dissolving properties for the active compound. Such substances are, for example, liquid hydrocarbons such as dioctylcyclo hexane, liquid paraffin, hydrocarbon resins such as 15 polyterpenes, in particular polypinene, or polar substances such as glycerol, di- and triglycerol or polyethylene glycols, e.g. having a molecular weight from 200 to 1000. These substances can form a homogeneous mixture with the polyacrylate adhesive or 20 else be contained therein as a separate phase. Glycerol and its derivatives especially are already present in low concentrations in the matrix as a separate phase, e.g. in the form of droplets. By means of the addition of such substances, it is in particular also possible 25 to compensate the higher saturation solubility in adhesives having free hydroxyl groups. Table 2 contains some data regarding the saturation solubilities of fentanyl in some of these substances. 30 Table 2: Saturation solubilities of fentanyl in solubility-decreasing additives -7 Substance Saturation solubility [% by weight] Polyethylene glycol 400 7.5 Glycerol < 1.5 Diglycerol < 1.5 Dioctylcyclohexane < 1.9 Paraffin, liquid < 1.5 The influence of such additives can be recognized by means of comparative permeation studies. 5 In table 3, the results of permeation studies with matrices based on a neutral polyacrylate adhesive having free hydroxyl groups with and without such additives and of a polyacrylate adhesive without other free functional groups are compared. All formulations 10 contain fentanyl in a concentration of 5% by weight. Table 3. Comparative permeation studies using formulations with and without solubility decreasing additives 15 Cumulated amount of permeated active compound [pg/cm2 Mean value of n = 3 * Formulation 4 h 8 h 24 h 48 h 72 h 2 0.00 0.23 7.89 32.82 64.17 3 0.798 4.46 29.6 68.9 103.1 4 0.805 4.87 32.6 74.7 113.2 * skin: human epidermis, female breast skin Formulation 2: 5% by weight fentanyl in a neutral polyacrylate adhesive with 5.2% free 20 hydroxyl groups Formulation 3: fentanyl 5.0% polyacrylate adhesive, neutral with 5.2% free 55.0% hydroxyl groups 5 polypinene 15.0% glycerol 10.0% dioctylcyclohexane 15.0% Formulation 4: 5% by weight of fentanyl in a 10 polyacrylate adhesive without free functional groups The results of the permeation study show that the permeation rate can be significantly improved by the 15 addition of substances reducing the solubility of the active compound in the matrix. Approximately the same results are achieved by the use of an adhesive without free functional groups, which even without additives has a low dissolving capacity for the active compound. 20 From the permeation data, the respective TTS sizes can be calculated for various TTS strengths. The results are listed in table 4. 25 Table 4: TTS sizes calculated from permeation data Release Calculated area sizes [cm 2 1 rate .Form. 1 Form. Form. Form. 3 Form. 4 2* 2** 25 pm/h 513 63.7 28.1 17.45 15.9 50 pm/h 1026 127.4 56.2 34.9 31.8 75 pm/h 1539 191.1 84.3 52.35 47.7 100 pm/h 2052 254.8 112.4 69.8 63.6 * calculated on the basis of the permeation data from table 1 ** calculated on the basis of the permeation data 30 from table 2 -9 The result of the calculation shows that carboxyl group-containing adhesives at a fentanyl concentration of 5% even at the lowest dose lead to TTS which are too 5 large for practical use. Although quite large TTS are also calculated in the case of the hydroxyl group containing adhesives, the possibility exists here due to the increase in the fentanyl concentration to arrive at TTS having a size suitable for practical use with 10 concentrations which are not too high, i.e. at most 20%. Simplified, it can be assumed here that the thermodynamic activity and thus also the permeation rates depend linearly on the concentration, as long as the active compound is present completely dissolved. 15 By use of the solubility-lowering auxiliaries in formulations having hydroxyl group-containing polyacrylate adhesives or by the use of polyacrylate adhesives without free functional groups, even at a 20 fentanyl concentration of 5%, TTS are obtained which have an acceptable size, even in the highest dose of 100 pg/h. Of course, the possibility also offers itself here of further reducing the system area by increasing the fentanyl concentration. 25 Fentanyl and its derivatives, as already mentioned at the outset, have a narrow therapeutic index. This means that for the action, on the one hand, a certain threshold value which must be exceeded with respect to 30 the plasma concentration, on the other hand unacceptable side-effects rapidly occur at higher concentrations. It is therefore advantageous if the system additionally contains a control membrane and thus the active compound flow through the skin is 35 restricted to a maximum value independently of the individual skin condition. Such membranes preferably consist of a copolymer of ethylene and vinyl acetate (EVA polymer) or are microporous films based on polyethylene or polypropylene. The prior art includes - 10 membranes of this type. In the case of the EVA polymers, the active compound permeability depends on the content of vinyl acetate and the thickness of the membrane. Membranes having a VA content of between 2 5 and 25 percent by weight and a thickness of between 25 and 100 pm, preferably between 40 and 100 pm, are customary, there being scarcely any limitations in practice with respect to the vinyl acetate content and the thickness. For the particular formulation, both 10 parameters must be chosen accordingly in order to guarantee restriction to the desired maximum flow from the TTS. In the case of the microporous membranes, the substance transport does not take place through the polymer, but only through the pores found in these 15 membranes. The number and size of the pores in this case determines the maximum release rate of the TTS. Customarily, such membranes are provided with an adhesive film for fixing the TTS to the skin. Adhesive 20 films based on self-adhesive polyacrylates or self adhesive polysiloxanes are particularly suitable for fentanyl and its derivatives. The advantage of poly siloxanes here is that the active compound in these polymers is very poorly soluble and therefore the 25 active compound loading of the TTS does not have to be increased unnecessarily by the use of an additional adhesive film. Adhesive films of this type, however, can also be used in systems which contain no membranes, but matrix layers having lower adhesive power. 30 As in any TTS, of course, there is also the possibility here of reducing the barrier properties of the human horny layer by the use of permeation-promoting substances. Such substances are, for example, fatty 35 acids, fatty alcohols, fatty acid esters, esters of glycerol with medium- or long-chain fatty acids and glycols such as 1,2-propanediol. All substances can be employed here which are physiologically acceptable and - 11 compatible with the active compound and the other excipients. In summary, it is to be observed the matrix systems 5 within the meaning of this invention show satisfactory to good permeation rates and also make possible the production of TTS having an acceptable size. At the same time, an endangering of the patient by an excessively high absorption of active compound as a 10 result of a leak is impossible. Overall, matrix systems based on polyacrylate adhesives within the meaning of this invention are thus an important advance in relation to the known prior art for fentanyl and its analogs with respect to patient safety. 15 Examples: Example 1 (formulation 1, 2, 4) 20 Fentanyl (free base) is dissolved in the solution of the adhesive in heptane/ethyl acetate. The amount of fentanyl is in this case calculated such that, based on the solids content of the adhesive solution, a concentration of 5.0% results. The resulting material 25 is coated using a doctor blade onto a siliconized polyester film protective layer to be removed before use, in a thickness such that, after the removal of the solvent, a weight of the coating of about 80 g/m 2 results. After the removal of the solvent, the dried 30 film is laminated with a thin polyester film (back layer of the TTS), and the finished TTS are stamped out of the complete laminate. Example 2 (formulation 3): 35 5.0 g of fentanyl, 15.0 g of polypinene, 10.0 g of glycerol, 15.0 g of dioctylcyclohexane and 110 g of the adhesive solution having a solids content of 50.0% are combined and stirred until the fentanyl has dissolved.

12 The resulting material is coating using a doctor blade onto a siliconized polyester film (protective layer to be removed before use) in a thickness such that, after the removal of the solvent, a weight of the coating of about 80 g/m 2 results. After the removal of the solvent, the dried film is laminated with a thin 5 polyester film (back layer of the TTS) and the finished TTS are stamped out of the complete laminate. Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the 10 presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims

1. A transdermal therapeutic system (TTS) comprising: a) an active compound-impermeable backing layer; b) at least one matrix layer based on polyacrylate and comprising a 5 fentanyl-analogous active compound selected from the group consisting of sulfentanyl, carfentanyl, lofentanyl and alfentanyl; and c) a protective film to be removed before use, wherein the polyacrylate is self-adhesive and free of carboxyl groups, has a saturation solubility for the active compound of between 10 3 and 20 percent by weight, and in that the at least one active compound containing layer contains at least 80 percent by weight of the incorporated active compound in molecularly disperse dissolved form.

2. The TTS according to claim 1, wherein the polyacrylate has a saturation solubility of between 4 and 12 percent by weight for the active compound. 15

3. The TTS according to claim 2, wherein the polyacrylate has a saturation solubility of between 5 and 10 percent by weight for the active compound.

4. The TTS according to any one of the preceding claims, wherein the polyacrylate has no free functional groups and is synthesized from a monomer mixture of acrylic or methacrylic acid esters only and, if appropriate, additionally 20 from other polymerizable vinyl compounds without free functional groups in amounts of up to 50% by weight.

5. The TTS according to claim 4, wherein the monomer mixture contains esters of acrylic and/or methacrylic acid of alcohols having 1 to 8 C atoms.

6. The TTS according to claim 4 or 5, wherein the monomer mixture contains 25 up to 20% by weight esters of acrylic and/or methacrylic acid of alcohols having 1 to 8 C atoms having a free hydroxyl group. 14

7. The TTS according to any one of claims 4 to 6, wherein the monomer mixture contains 2-ethylhexyl acrylate, n-octyl acrylate, proply acrylate, n-butyl acrylate, isobutyl acrylate and/or the corresponding methacrylates.

8. The TTS according to any one of claims 4 to 7, wherein the monomer 5 mixture contains 2-hydroxyethyl acrylate and/or 2-hydroxyethyl methacrylate.

9. The TTS according to any one of claims 4 to 8, wherein the monomer mixture contains vinyl acetate.

10. The TTS according to any one of claims 1 to 9, wherein the polyacrylate is prepared by free-radical polymerization of a monomer mixture. 10

11. The TTS according to any one of claims 1 to 10, wherein the polyacrylate contains free hydroxyl groups and is crosslinked by polyvalent cations or reactive substances.

12. The TTS according to any one of claims 1 to 11, wherein the polyacrylate contains free hydroxyl groups and is crosslinked with A13+, Ti 4 * or melamine. 15

13. The TTS according to any one of claims 1 to 12, wherein the active compound-containing layers additionally contain substances for improving the permeation rate through human skin.

14. The TTS of claim 13, wherein the additional substances are selected from the group consisting of glycols, fatty acids, fatty acid esters, fatty alcohols and 20 glycerol esters or mixtures thereof.

15. The TTS according to any one of claims 1 to 14, wherein the active compound-containing layers contain substances which lower the solubility of the active compound in these layers.

16. The TTS according to claim 15, wherein the substances that lower the 25 solubility are selected from: 15 a) hydrocarbons which are liquid at room temperature, including dioctylcyclohexane or liquid paraffin; and b) hydrocarbons resins, including polypinene resins or polyethylene glycol or glycerol. 5

17. The TTS according to any one of claims 1 to 16, further comprising a control membrane as a further layer.

18. The TTS according to claim 17, wherein the control membrane consists of an ethylene/vinyl acetate copolymer, preferably having a vinyl acetate content of up to 25% by weight. 10

19. The TTS according to claim 17, wherein the control membrane consists of a microporous film based on poly-ethylene or polypropylene.

20. The TTS according to any one of claims 17 to 19, wherein the control membrane has a thickness of between 25 and 100, preferably between 40 and 100 pm. 15

21. The TTS according to any one of claims 17 to 20, further comprising a self adhesive layer situated toward the skin on the control membrane for fixing to the skin. LTS LOHMANN THERAPIE - SYSTEME AG WATERMARK PATENT & TRADE MARK ATTORNEYS P23625AU00