Particulate materials
The present invention relates to active substances in particulate form, to methods for preparing them and to their uses. The present invention provides particulate powders, such as might be of use for delivery using a dry powder inhaler (DPI) or similar delivery device, having properties which may be beneficial to the DPI delivery process.
1. An active substance in particulate form suitable for administration via a dry powder inhaler, said particulates comprising:
a) a volume mean aerodynamic diameter of less than 7 microns;
b) a density less than 0.5 g/ml; and
c) a surface-to-volume ratio of at least twice that of spherical particles of the same volume diameter.
2. An active substance as in claim 1 wherein the surface-to-volume ratio is at least 2.5 times that of spherical particles of the same volume diameter.
3. An active substance of claim 1 further comprising a shape factor of at least 2.
4. An active substance of claim 1 further comprising a shape coefficient of greater than 10.
5. An active substance of claim 1 further comprising comprising an aerodynamic shape factor of at least 1.4.
6. An active substance of claim 1 further comprising a specific surface area of at least 10 m 2 /g.
7. An active substance of claim 1 further comprising a specific surface area of at least 15 m 2 /g.
8. An active substance of claim 1 further comprising a specific surface area of at least 20 m 2 /g.
9. An active substance of claim 1 further comprising a specific surface area of at least 25 m 2 /g.
10. An active substance of claim 1 further comprising a volume mean diameter of less than 6 microns.
11. An active substance of claim 1 further comprising a specific surface energy of less than 100 mJ/m 2 .
12. An active substance of claim 1 further comprising a specific surface energy of less than 70 mJ/m 2 .
13. An active substance of claim 1 further comprising an aggregate tensile strength less than 0.8.
14. An active substance of claim 1 further comprising a surface weighted domain size of at least 400 Å.
15. An active substance of claim 1 further comprising a volume weighted domain size of at least 700 Å.
16. An active substance of claim 1 further comprising a total strain less than 0.7×10 −3 .
17. An active substance of claim 1 further comprising a mean specific charge from −5 to +5 nCg −1 .
18. An active substance of claim 1 further comprising a RMS roughness, measured using atomic force microscopy (AFM), of 0.5 nm or less.
19. An active substance of claim 1 further comprising a dispersive component of surface free energy, Ys D , which is at least 5% lower than for the corresponding active substance made by micronization, granulation, or solvent crystallization.
20. An active substance of claim 1 further comprising a specific component of free surface energy absorption, ΔG A , which is at least 10% lower than for the corresponding active substance made by micronization, granulation, or solvent crystallization.
21. An active substance of claim 1 further comprising a mean adhesion fraction following triboelectrification in a turbula mixer which is 50% or less of that for the same active substance made by micronization, granulation, or solvent crystallization.
22. An active substance of claim 1 further comprising a theoretical aggregate tensile strength, σ, which is no more than 0.8 times that for particles of the same active substance made by a micronization, granulation, or solvent crystallization.
23. An active substance of claim 1 further comprising a particle size distribution (X 90 ) of from 0.5 to 10 μm.
24. An active substance of claim 1 further comprising a particle size spread, measured using a cascade impacted technique at low turbulence, which is at least 5% smaller and with a mean diameter which is at least 10% smaller than that of the corresponding active substance made by micronization, granulation, or solvent crystallization.
25. An active substance of claim 1 further comprising a total crystal strain, ε, which is at least 30% lower than that for particles of the same active substance made by micronization, granulation, or solvent crystallization.
26. An active substance of claim 1 further comprising an amorphous phase content which is at least 10 times lower than that for particles of the same active substance made by micronization, granulation, or solvent crystallization.
27. An active substance of claim 1 further comprising a mean specific charge following triboelecrification which is at least 50% lower than for the corresponding active substance made by micronization, granulation, or solvent crystallization.
28. An active substance of claim 1 further comprising a mean avalanche time as determined using a powder avalanching apparatus which is at least 5% lower at 100 s/rev than for the corresponding active substance made by micronization, granulation, or solvent crystallization.
29. An active substance of claim 1 further comprising a mean avalanche time as determined using a powder avalanching apparatus which is at least 10% lower at 145 s/rev than for the corresponding active substance made by micronization, granulation, or solvent crystallization.
30. An active substance of claim 1 further comprising an amorphous phase content of less than 1% w/w.
31. An active substance of claim 1 further comprising a bulk powder density of 0.2 g/cm 3 or less.
32. An active substance of claim 1 further comprising a shape factor of at least 3.5.
33. An active substance of claim 1 further comprising a root mean square (RMS) roughness, measured using atomic force microscopy, of 0.2 nm or less.
34. An active substance of claim 1 which, when delivered using a passive dry powder inhaler, yields a fine particle fraction in the emitted dose of 20% or greater.
35. An active substance according to claim 34 which yields a fine particle fraction in the emitted dose of 31% or greater.
36. An active substance according to claim 34 which yields a fine particle fraction in the emitted dose of 55% or greater.
37. An active substance according to claim 1 comprising a pharmaceutically or nutraceutically active substance.
38. An active substance according to claim 37 wherein the active substance is a pharmaceutically active substance or a mixture thereof.
39. An active substance according to claim 38 wherein the active substance is selected from the group consisting of salbutamol, terbutalene, salmeterol, fenoterol, bromocriptine or a pharmaceutically acceptable salt or mixture thereof.
40. A method of administering an active substance by inhalation comprising providing a composition according to claim 1 and administering said composition to the respiratory tract.
41. A method according to claim 40 wherein the composition is administered via a passive dry powder inhaler.