Powders
Particles of an amino acid such as leucine may be formed from an amino acid vapor, for example by aerosol condensation, or by spray drying. The amino acid particles have a bulk density of not more than 0.1 gcm −3 or have a mass median aerodynamic diameter of not more than 10 μm or are in the form of flakes having a thickness of not more than 100 μm. The inclusion of the particles of amino acid in powder for use in dry powder inhalers has been found to improve the respirable fraction of the active material in the powder.
1. Amino acid particles, in which the particles have a bulk density not more than 0.1 gcm −3 .
2. Amino acid particles according to claim 1 , in which the particles have a bulk density not more than 0.05 gcm −3 .
3. Amino acid particles having a mass median aerodynamic diameter (MMAD) not more than 5 μm.
4. Amino acid particles being in the form of flakes having a thickness of not more than 0.5 μm.
5. Amino acid particles according to claim 4 in which the flakes having a thickness of not more than 100 nm.
6. Amino acid particles according to claim 1 , in which the amino acid is leucine.
7. A powder for use in a dry powder inhaler, the powder including active material and amino acid particles according to claim 1 .
8. A powder according to claim 7 , in which the powder includes not more than 20% by weight of amino acid based on the weight of the powder.
9. A powder according to claim 8 , in which the powder includes not more than 10% by weight of amino acid based on the weight of the powder.
10. A powder for use in a dry powder inhaler, said powder including active material, particles of a diluent, and amino acid particles in which the amino acid particles have a bulk density of not more than 0.1 gcm −3 .
11. A powder according to claim 10 , in which the diluent includes a crystalline sugar.
12. A powder according to claim 10 , in which the diluent has a particle size such that at least 90% by weight of the diluent particles have a particle size not more than 10 μm.
13. A powder according to claim 10 , in which the diluent has a particle size such that at least 90% by weight of the diluent particles have a particle size not less than 50 μm.
14. A powder according to claim 10 , in which the diluent has a fine particle portion having a particle size such that at least 90% by weight of the particles of the fine particle portion have a particle size not more than 10 μm and a coarse particle portion having a particle size such that at least 90% by weight of the particles of the coarse particle portion have a particle size not less than 50 μm.
15. A powder according to claim 14 , in which the fine particle portion and coarse particle portion comprise the same material.
16. A powder according to claim 14 , in which the powder includes not more than 5% by weight of the fine particle portion based on the weight of the powder.
17. A powder according to claim 14 , in which the powder includes not more than 95% by weight of the coarse particle portion based on the weight of the powder.
18. A dry powder inhaler, the inhaler containing powder, wherein said powder includes active material and amino acid particles in which the amino acid particles have a bulk density of not more than 0.1 gcm −3 .
19. A method of preparing particles of amino acid, the method including the step of forming solid amino acid particles from a vapor or from a solvent, the method being such that the particles are formed while being suspended in a gas flow, said particles having a mass median aerodynamic diameter (MMAD) not more than 5 μm.
20. A method of preparing particles of amino acid, the method including the step of condensing amino acid vapor to form solid amino acid particles, wherein said amino acid particles have a bulk density not more than 0.1 gcm −3 .
21. A method according to claim 19 , in which particles of amino acid are formed by aerosol condensation.
22. A method according to claim 20 , in which the method includes the steps of
a) heating the amino acid so that the amino acid forms a vapor;
b) mixing the amino acid vapor with cool air to form a cloud of condensed amino acid particles; and
c) collecting the condensed particles.
23. A method according to claim 20 , the method including the step of heating the amino acid particles to a temperature of at least 150° C. at ambient pressure.
24. A method according to claim 19 , in which the method includes the step of spray drying to form solid particles of amino acid.
25. A method according to claim 24 , in which the material to be dried comprises amino acid in solution.
26. A method according to claim 19 , in which the method is such that the MMAD of the solid amino acid particles produced is not more than 10 μm.