INTRAUTERINE DEVICE, AND A METHOD OF REDUCING THE RATE OF DIFFUSION OF ACTIVE INGREDIENTS IN SAID INTRAUTERINE DEVICE

Abstract

An intrauterine device having at least one first pharmaceutically active ingredient and at least one first layer made of at least a first polymeric material, wherein between about 10 and about 60 v/v % of at least one particulate material is dispersed and/or incorporated in the first polymeric material. The presence of the particulate material will reduce the porosity of the polymer or otherwise obstruct the diffusion of the pharmaceutically active ingredient being released, thereby slowing its rate of release. In this way, it is possible to regulate the release rate and/or initial burst of the device, simply by adjusting the amount of particles/particulate material in the first layer, instead of having to adapt the size of the device to the desired release pattern, which requires expensive changes in production equipment and manufacturing processes.

Claims

1. An intrauterine device comprising at least one first pharmaceutically active ingredient and at least one first layer made of at least a first polymeric material having dispersed therein between 10 and 60 v/v % of at least one particulate material that obstructs the diffusion of the pharmaceutically active ingredient being released, wherein the particulate material is inert, has a mean particle diameter of between 3.6 μm and 100 μm as measured by laser scattering using volumetric measurements based on an approximately spherical particle shape, and has forms a geometric structure wherein molecules of the at least one active ingredient are contained within spaces of the geometric structure between the particulate material.

2. An intrauterine device according to claim 1, wherein the at least one particulate material is an inert inorganic or organic material.

3. An intrauterine device according to claim 1, wherein the at least one particulate material has a mean particle size of no greater than 50 μm; no greater than 30 μm, no greater than 20 μm, or 10 μm.

4. An intrauterine device according to claim 1, wherein the at least one particulate material is selected from the group comprising magnesium stearate, bentonite, talc, clay, calcium stearate, stearic acid, sodium steatyl fumarate and calcium sulphate.

5. An intrauterine device according to claim 1, wherein the at least one particulate Material is talc.

6. An intrauterine device according to claim 1, where the at least one particulate material is surface-treated and/or modified to alter the three-dimensional shape or the hydrophilic/hydrophobic properties of the material.

7. An intrauterine device according to claim 1, wherein the thickness of the at least one first layer is between 0.05 mm and 3 mm, between 0.05 mm and 2 mm, between 0.1 mm and 2 mm or between 0.2 mm and 1 mm.

8. An intrauterine device according to claim 1, wherein an outer layer of the intrauterine device is the at least one first layer.

9. An intrauterine device according to claim 1, wherein the at least one pharmaceutically active ingredient is incorporated/dissolved in at least one second layer which may be made of at least one second polymeric material, and wherein said at least one first layer at least partly encapsulates said second layer.

10. An intrauterine device according to claim 9, wherein said at least one second layer is divided into sections, each of which comprises an individual active ingredient.

11. An intrauterine device according to claim 9, wherein said at least one first layer does not contain any pharmaceutically active ingredient(s).

12. An intrauterine device according to claim 9, which further comprises a central inert core that does not contain any active ingredient, and wherein said at least one second layer at least partly encapsulates the core, and said at least one first layer at least partly encapsulates said second layer.

13. An intrauterine device according to claim 12, wherein the core is made of a thermoplastic polymer, and the first and second polymeric material of the first and second layers respectively, are a thermoset elastomer or silicone.

14. An intrauterine device according to claim 9, wherein the at least first polymeric material of the first and/or second layer, and optionally the core, is at least one inert thermoset or thermoplastic elastomer.

15. An intrauterine device according to claim 14, wherein the thermoset elastomer is a pharmaceutically acceptable silicone or polydimethylsiloxane.

16. An intrauterine device according to claim 1, wherein the at least one active ingredient is at least one contraceptive agent, an estrogenic steroid, or a progestational steroid.

17. An intrauterine device according to claim 1, wherein the at least one active ingredient is at least one spermicide, an antimicrobial agent or an anti-viral agent.

18. An intrauterine device according to claim 1, which is a vaginal ring.

19. A method for reducing the rate of diffusion of an active ingredient though a polymeric material in an intrauterine device, wherein said method comprises incorporating the at least one particulate material into said polymeric material, thus forming the intrauterine device of claim 1.

20. A method of manufacturing an intravaginal ring according to claim 19, wherein the at least one first layer is prepared by injection moulding or by extrusion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The invention will be explained in greater detail below, describing only exemplary embodiments of the IUDs according to the invention.

[0064] FIG. 1 shows a perspective view the of a first embodiment of a vaginal ring according to the invention, having a shell design.

[0065] FIG. 2 shows a perspective view of a second embodiment of a vaginal ring according to the invention, having a reservoir design.

[0066] FIG. 3 shows a cross section view of a third embodiment of a vaginal ring according to the invention, having a reservoir design.

[0067] FIG. 4 depicts the release of ethinyl estradiol from the samples in example 2.

DETAIL DESCRIPTION OF THE INVENTION

[0068] The invention is described with the assumption that the IUD is a vaginal ring. However, this assumption is not to be construed as limiting, and the IUD can just as easily have a different structure/design, or be a different kind of IUD, e.g. a hormone spiral.

[0069] FIG. 1 shows a perspective view of a first embodiment of an intravaginal ring 1 according to the present invention having a shell design. Said ring comprises a core 2, a second layer 3 and a first layer 4 encapsulating the second layer. The core 2 is a thermoplastic polymer and each layer 3, 4 is preferably made of an inert polymer, preferably a pharmaceutical acceptable silicone.

[0070] In the second layer 3 is dispersed and/or dissolved at least one pharmaceutically active ingredient 5 and in the first layer 4 is dispersed/incorporated between 10 and 60 v/v % least one particulate material 6.

[0071] FIG. 2 shows a second embodiment of a vaginal ring according to the invention, having a reservoir design. In said embodiment the second layer 3′, containing the active ingredient 5, constitutes a central core 7, i.e. a drug-loaded polymer core, which is encapsulated by the first layer 4, containing the particulate material 6, in a similar manner as in FIG. 1.

[0072] FIG. 3 shows a third embodiment 1″, which is a variant of the embodiment shown in FIG. 1. For like parts same reference numbers are used. In said embodiment the second layer 3″ has been divided into two sections 3a, 3b, each of which comprises an individual active ingredient 5a, 5b. Said design has the advantage that each section 3a, 3b of the second layer 3″, can be manufactured independently, enabling use of different polymeric material with different properties, and accordingly different diffusion characteristics in the individual sections.

[0073] The presence of the particulate material 6 in the first layer of all embodiments reduces the porosity of the polymer or otherwise obstructs the diffusion of the pharmaceutically active ingredient 5 being released from the second layer 3, thereby increasing the length of the path of the diffusion through the polymer of the first layer. Furthermore, since some of the polymeric material has been replaced with the particulate material in the first layer 4, the amount of dissolved active ingredients, which can be dissolved in the polymeric material, has been reduced. Accordingly, buildup of active ingredient in the first layer is difficult, simply since lower concentrations of active ingredient can be dissolved in the first layer.

[0074] In this way, it is possible not only to regulate the release rate of the IUD, simply by adjusting the amount of particles/particulate material in the first layer 4, but it is also possible to provide a more reliable release rate and a lower initial burst, compared with the release rate and initial burst from a similar IVR without the added particles 6 in the first layer 4.

[0075] The geometrical structure of the particulate material 6 is preferably a flat structure and/or a layered structure, enabling the molecules of the at least one active ingredient 5 to be contained within spaces between the flat particulate material. However, a person skilled in the art will understand that the particulate material in principal can have any three-dimensional shape a s long as the length of the path of the diffusion through the first polymer is increased such that the release rate of active ingredient is reduced.

[0076] In a similar manner as for the first layer, the particulate material can be dispersed/incorporated in the second layer containing the active ingredient. Alternatively or in combination, the first layer can comprise one or more active ingredients.

[0077] The embodiments shown in the figures comprise only one first and one second layer, however a person skilled in the art will understand that several first and second layers are contemplated within the scope of the invention.

EXAMPLES

[0078] In order to evaluate if a particulate material having a mean particle size between 0.1 μm and 100 μm and incorporated in a concentration between 10 and 60 v/v % in a first layer had any effect on the release rate and/or initial burst of an active ingredient contained in a second layer, a number of samples was constructed. In all samples the first layer encapsulates the second layer. Accordingly, the first layer functions as a membrane and the second layer functions as a drug-containing core.

[0079] A conventional moulding technique was used for preparing the relevant samples. The first and second layers were formed in separate steps. The particulate material were mixed with the polymer of the first layer; and active ingredient were mixed with the polymer of the second layer. The ingredients of the respective layers were thoroughly mixed in a SpeedMixer DAC-150. The formed mixes were subsequently injected into appropriate moulds, and allowed to cure for a period of time using a predetermined temperature, depending on the polymer. For all samples the diameter of the core was 1 mm.

[0080] In vitro release of the active ingredient in the samples were conducted with a typical dissolution test for vaginal rings, the samples were submerged in a glass flask containing 250 ml water (example 1) or 400 ml water medium (example 2 and 3) subjected to shaking of 130 rpm at 37° C. Samples were withdrawn after appropriate time periods, and the concentration was determined with an HPLC method.

Example 1

[0081] In the present experiment the first layer was made of polydimethylsiloxane (obtainable from NuSil Technology LLC) with varying amounts of talc (obtainable from Imerys Talc) as particulate material. The used talc had a mean particle size of 19.3 μm determined by laser diffraction. The second layer was made of polydimethylsiloxane (obtainable from NuSil Technology LLC) having a concentration of 0.1 w/w % estradiol (obtainable from Sigma-Aldrich Co. LLC).

[0082] The first layer was cured at 130° C. The second layer containing the estradiol was cured at room temperature.

[0083] Five different samples were manufactured, two of which contained no particulate material, and three having increasing amounts of particulate material in the first layer.

[0084] The samples were analysed for in-vitro drug release using the dissolutions test described above, and the results are shown in table 1.

TABLE-US-00001 TABLE 1 in-vitro release of estradiol from the five samples. Thickness of first Amount of talc Amount of talc Estradiol No. layer (mm) (w/w %) (v/v %) (μ/24 hours) I 1.0 0 0 2.10 II 0.6 0 0 3.42 III 0.6 20 8.5 2.43 IV 0.6 40 20 1.38 V 0.6 60 36 0.79

[0085] Sample I and II resemble the prior art, i.e. IVRs not having any particulate material incorporated into the first layer. When comparing sample no. V (comprising 36 v/v % particulate material) with the control sample having similar thickness of the first layer, i.e. ring no. II, it is evident that the release rate had been decreased more than four times. It means that the first layer can be made four times thinner, yielding a smaller product with lower or no initial burst.

Example 2

[0086] In order to further investigate the impact of the concentration of the particulate material in relation to the thickness of the first layer, a number of additional samples were constructed using the method described above.

[0087] In the present experiment the first layer (membrane) was made of polydimethylsiloxane with different amounts of talc (obtainable from Imerys Talc) having varying mean particle sizes. The mean particle sizes determined by laser diffraction of the talc used, are as follows: pharma grade: 19.3 μm, M grade: 10.5 μm and UM grade: 3.6 μm.

[0088] The second layer (core) was made of polydimethylsiloxane. Said core had nine parts by weight of polydimethylsiloxane and one part by weight of ethinyl estradiol (obtainable from Bayer Pharma AG). (i.e. the core contains 10 w/w % ethinyl estradiol).

[0089] The polydimethylsiloxanes were cured at 70° C. for 15 minutes.

[0090] The used polydiinethylsiloxanes (both core and membrane) are a MEDS-6381 silicone, obtainable from NuSil Technology LLC, and has a low viscosity (˜40,000 mPas). Said polydimethylsiloxane comprises a tin catalyzed cure system (condensation cure) and does not contain fumed silica.

[0091] Thirteen different samples were manufactured with this method, four of which contained no particulate material.

[0092] In order to evaluate the initial burst of active ingredient, i.e. the amount of released ingredient in the first day, the samples were stored at 25° C. and 60% RH in three weeks prior to analysis to allow the active ingredient to diffuse into the first layer (membrane).

[0093] The samples were analysed for in-vitro drug release using the dissolutions test described above, and the results are shown in table 2.

TABLE-US-00002 TABLE 2 in-vitro release of ethinyl estradiol from the samples, no 1-13. Thickness Particle Day 1 Day 2 Day 3 Day 8 Day 15 of first size Particles Particles (μg/24 (μg/24 (μg/24 (μg/24 (μg/24 No. layer Particles (μm) (w/w %) (v/v %) hours) hours) hours) hours) hours) 1 0.25 — — 0 0 204.4 163.7 158.9 152.9 121.9 2 0.5 — — 0 0 93.2 77.1 79.1 80.5 73.0 3 1 — — 0 0 90.3 51.3 49.6 49.9 45.5 4 2 — — 0 0 134.4 47.8 46.3 30.6 27.9 5 0.25 Talc P. 19.3 40 20 88.2 59.1 62.3 68.5 62.8 6 0.5 Talc P. 19.3 40 20 84.0 43.3 40.5 40.2 39.3 7 1 Talc P. 19.3 40 20 72.6 28.6 26.1 22.5 22.0 8 0.25 Talc P. 19.3 60 36 40.9 28.8 32.5 36.3 31.6 9 0.5 Talc P. 19.3 60 36 28.1 17.2 16.5 17.2 17.1 10 1 Talc P. 19.3 60 36 24.9 9.6 8.3 10.3 9.8 11 0.5 Talc P.M 10.5 40 20 64.2 34.1 33.4 33.6 35.4 12 0.5 Talc 3.6 40 20 41.7 23.6 26.9 26.1 27.4 P.UM 13 — Silica 0.012 25.7 13.6 — — — — —

[0094] Release rate. Samples no. 1 to 4 resembles the prior art, i.e. 1VRs not having any particulate material incorporated into the first layer (membrane).

[0095] Similar to the findings in example 1, the release rate of ethinyl estradiol is decreased significantly when the particulate material is incorporated into a vaginal ring. Furthermore, the initial burst is higher for the prior art samples than for the sample according to the invention.

[0096] This is even more evident from FIG. 4 which is a graphical representation of the results in table 2, clearly showing that the initial burst is affected by both the size of the particles and the concentration in the first layer.

[0097] As an example can be mentioned that sample no. 4 (2 mm thickness of the first layer—no particles), releases 30.6 μg ethinyl estradiol per day at day 8. Said release rate can be compared to the release rate on day 8 of samples no. 12 (0.5 mm thickness of the first layer having a content of 20 v/v % talc with a mean particle size of 10.5 μm), having a release rate of 26.1 μg/day. However, if the same samples, i.e. samples no. 4, and 12 are compared for the initial burst at day 1, it is clear that the prior art (represented by sample no. 4) has a more than three times higher initial burst of 134.4 μg than the embodiment according to the invention (represented by sample no. 12), having a release rate of 41, 7 μg/day, even though the first layer of the prior art sample is four times thicker than the first layer of the sample according to the invention.

[0098] Thus, the samples according to the invention comprising 20 v/v % talc in the first layer (e.g. const. no. 6 and 7) have a thinner first layer of between 0.5 and 1 mm and a significantly lower burst between 72.6-84.0 μg at day 1 compared to the prior art samples. The thinner membrane will result in a smaller product with lower cost((saves on raw material cost) but will also in many situations improve the patients' acceptance factor (a large vaginal ring is often perceived with discomfort). By increasing the amount of particulate material further to 36 v/v %, i.e. sample no. 8-9, an even thinner membrane and much lower burst of less of 40 μg/day (in-between 28.1 and 40.9 μg/day) can be achieved than for the prior art sample having an 134 μg/day drug release at day 1.

[0099] The examples further showed that the mean particle size of the particulate material had great impact on the viscosity of the talc and silicone mix and it also had an impact on the drug release rate, both at day 8 and on the initial burst at day 1. Comparing sample no. 6, 11 and 12, having same thickness of the first layer, but having different mean particles sizes of the particulate material, it is clear that the drug release which at day 8 was 40.2 μg/day with the large particle size (19.3 μg), decreased to 33.6 μg/day with the medium particle size (10.5 μg) and decreased further to 26.1 μg/day with the small particle size (3.6 μg).

[0100] Thus, it can be concluded that the initial burst also was affected by the particle size, whereby the initial burst decreased with decreasing particle size.

[0101] Viscosity during mixing. Traditional injection molding equipment and techniques are intended to accommodate materials which can be melted to yield low viscosities. It is commonly understood that materials having a viscosity greater than about 8 kilopoise, including materials, e.g. silicone, with a degree of fill greater than about 40% by volume, are unsatisfactory to process.

[0102] During the manufacturing of the samples no. 1-13 it was noted that when the particulate material was added to the polymer, the viscosity of the mixture of particulate material and polymeric material increased.

[0103] For sample no. 5-7 with 20 v/v % talc with large particle size (19.3 μm) a moderate visual increase in viscosity was observed. For sample no. 8-10 with 36 v/v % talc with large particle size (19.3 μm) a high increase in viscosity was observed, but it was still possible to use the mixture for injection molding. Example 11 with 20 v/v % talc with medium particle size (10.5 μm) gets a significant visual increase in viscosity but it was still possible to use the mixture for injection moulding. Sample no. 12 with 40 w/w % talc with small particle size was very similar to example 8-10 in respect of viscosity. Thus the talc did not alter the physical and/or chemical properties of the polymeric material(s) or active ingredient(s) negatively, i.e. the properties of the polymer was not altered to such an extent that the polymeric material cannot be processed and/or used for the intended purpose, i.e. as a IUD.

[0104] In sample no. 13; 40 w/w % silica (fumed silica) was attempted to be mixed into the silicone polymer. Said silica had a particle size of 0.012 μm and was obtainable from Wacker Chemie AG. When 25.7 w/w % (˜13.6 v/v %) was added to the polymer, the attempt was halted since the mix became too stiff to continue mixing. Thus, it is clear that trying to add high concentrations of silica, negatively affected the physical properties of the polymer, thereby making it unsuitable for further processing, e.g. for injection moulding, and thereby accordingly also unsuitable for use as an intrauterine device. Thus, that particulate material having a size below 0.1 μm, is not suitable as a particulate material in the present invention.

Example 3

[0105] Six additional samples were made, using the method described above, to further demonstrate the impact of the size of the particulate material added to the first layer (membrane), in the form of talc (particle size above 0.1 μm) and/or fumed silica (particle size below 0.1 μm).

[0106] The samples each contain a second layer in the form of a core. Said core contains three parts by weight of MED-4286 silicone and one part by weight of drospirenone (obtainable from Sterling S.p.A.) (i.e. the core contains 25 w/w % drospirenone). Said silicone does not comprise fumed silica.

[0107] The samples each comprises a first layer made of different silicones. In all samples the first layer had a thickness of 0.5 mm and had different amounts of talc (obtainable from Imerys Talc) and/or different amounts of fumed silica (silica). The mean particle sizes of the talc used, as determined by laser diffraction, were: Pharma grades: 19.3 μm; M grade: 10.5 μm and UM grade: 3.6 μm. The fumed silica had a particle size of 0.012 μm and was obtainable from Wacker Chemie AG.

[0108] The used silicones are all obtainable from NuSil Technology LLC, and were cured from 90 to 130° C. for 10 minutes.

[0109] In order to evaluate the initial burst of active ingredient, i.e. the amount of released ingredient in the first day, the samples were stored under room conditions for three weeks prior to analysis to allow the active ingredient to diffuse into the first layer.

[0110] The samples were analyzed for in-vitro drug release using the dissolutions test described above, and the results can be seen in table 3.

TABLE-US-00003 TABLE 3 in-vitro release of drospirenone for the samples no. 14-19 Particle Day 1 Day 3 Day 3 Day 8 Day 15 Silicone of first size Particles Particles (μg/24 (μg/24 (μg/24 (μg/24 (μg/24 No. layer Particles (μm) (w/w %) (v/v %) hours) hours) hours) hours) hours) 14 MED-6010 — — 0 0 352 331 360 375 372 (0 v/v % silica) 15 MED-4917 — — 0 0 483 397 406 417 409 (13 v/v % silica) 16 MED4-4420 — — 0 0 438 370 401 419 427 (10 v/v % silica) 17 MED4-4420 Talc P. 19.3 40 20 186 161 168 181 188 (10 v/v % silica) 18 MED4-4420 Talc P.M 10.5 40 20 181 148 152 168 170 (10 v/v % silica) 19 MED4-4420 Talc P.UM 3.6 40 20 194 160 161 175 168 (10 v/v % silica)

[0111] By comparing sample no. 14-16 with samples no. 17-19, it is evident that adding talc to the silicone polymers significantly lowered the drug release rate at day 8. It is also clear that the amount of fumed silica in the silicone polymers does not substantially decrease the drug release rate, thus it is clear that the fumed silica has no significant effect on the release rate, this is due to the fact that fumed silica has a mean particle size of 0.012 μm, which is below 0.1 μm.

[0112] It is furthermore clear that both the initial burst and release rate of active ingredient and was smaller when talc was added to the first layer, compared to the samples without talc.

[0113] The particle size of the added particles is relevant. Too small particle size causes a stiff mix already at modest concentrations. It is possible to choose a particle size that benefits the imperative. The use of large particle size facilitates high loading. The talc with approx. 10 μm particle size has a favorable balance. Said size has e.g. shown a soft and smooth mix with thixotropic behavior that counteract potential dripping and segregation with a loading of 20 v/v %.

[0114] From example 2 and 3 it can be concluded that particulate material, such as fumed silica, having a particle size smaller than about 0.1 μm (medium particle size determined by laser scattering) is not suitable for the present invention. The net effect of adding silica (particles which are smaller than 0.1 μm) on drug release is neglectable, and is likely a consequence of the high surface area of small particles that cause strong interactions with the silicones' physical properties, i.e. the uncured silicone becomes too stiff if the silicone is not adjusted to accommodate the silica. Test 15 and 16 use silicone that are adjusted to accommodate silica and does not show slower drug release compared to the test 14 that do not contain silica, accordingly it is important the particles have a mean particles size above 0.1 μm, preferably even higher.

[0115] it is furthermore evident from the above examples that the release rate is decreased significantly when the particulate material is incorporated into a first layer of a vaginal ring. Comparing prior art samples, i.e. samples having no particulate material in the first layer, with samples according to the invention, i.e. samples having particulate material in the first layer, it is evident that the release rate is significantly decreased.

[0116] This means that the first layer can be made thinner, yielding a smaller product with lower or no initial burst. Consequently, the manufacturing costs associated with IVRs according to the invention are considerably reduced and the user acceptability is highly increased.

[0117] The IUD according to the invention has a simple inexpensive design, and can therefore be used equally well both privately and in medical or hospital facilities.

[0118] Modifications and combinations of the above principles and designs are foreseen within the scope of the present invention.