Carrier particles for use in dry powder inhalers

1. A powder for use in a dry powder inhaler, the powder comprising active particles, carrier particles for carrying the active particles and an additive material onto surfaces of the carrier particles, wherein the additive material is: (a) a particulate, consisting of particles with a mass median diameter of not more than about 10 μm having a surface area of at least 5 m 2 g −1 ; (b) surface active; (c) present in an amount that forms no more than 10% by weight of the powder and such that the powder has sufficient post-vibration homogeneity to have a coefficient of variation of less than about 5%; and (d) capable of promoting the release of the active particles from the carrier particles on actuation of the inhaler, wherein the active particles are likely to be retained by the carrier particles before actuation of the inhaler.

2. A powder according to claim 1 wherein the powder includes not more than 5% by weight of additive material based on the weight of the powder.

3. A powder according to claim 2 wherein the powder includes not more than 2% by weight of additive material based on the weight of the powder.

4. A powder according to claim 1 wherein the carrier particles are comprised of one or more crystalline sugars.

5. A powder according to claim 4 wherein the carrier particles are particles of lactose.

6. A powder according to claim 1 wherein substantially all (by weight) of the carrier particles have a diameter which lies between 20 μm and 1000 μm.

7. A powder according to claim 1 wherein the additive material consists of physiologically acceptable material.

8. A powder according to claim 1 wherein the additive material includes one or more compounds selected from amino acids, and peptides and polypeptides having a molecular weight from 0.25 to 1000 KDa.

9. A powder according to claim 8 wherein the additive material includes an amino acid.

10. A powder according to claim 9 wherein the additive material consists substantially of leucine.

11. A powder according to claim 1 wherein the additive material includes one or more water soluble materials.

12. A powder according to claim 11 , wherein the additive material comprises a phospholipid.

13. A powder according to claim 12 , wherein the additive material comprises soya lecithin.

14. A powder according to claim 1 , wherein the additive material includes or consists of one or more surface active materials.

15. A powder according to claim 1 , wherein the additive material is an anti-adherent material.

16. A powder according to claim 1 , wherein the additive material is an anti-friction agent.

17. A powder according to claim 1 , wherein the additive material includes dipolar ions.

18. A powder according to claim 17 wherein the additive material consists of zwitterions.

19. A powder according to claim 1 wherein the particles of additive material are attached to the surfaces of the carrier particles.

20. A powder according to claim 1 wherein the powder consists of not less than 0.1% by weight of additive particles based on the weight of the carrier particles.

21. A powder according to claim 1 wherein the particles of additive material form a discontinuous covering on the surfaces of the carrier particles.

22. A powder according to claim 21 wherein the additive materiai, whilst forming a discontinuous covering on the surfaces of the carrier particles saturates the surfaces of the carrier particles.

23. A powder according to claim 1 wherein the mass median diameter of the active particles is not more that 10 μm.

24. A powder according to to claim 1 wherein the active particles include a β 2 -agonist.

25. A powder according to claim 24 wherein the active particles include salbutamol, a salt of subutamol or a combination thereof.

26. A powder according to claim 1 wherein the active particles include beclomethasone dispropionate.