Drug delivery system

1. A method comprising:

orally administering to a subject a formulation comprising:

a drug delivery system comprising an intercalate of a layered double hydroxide having, before intercalation, layers of metal hydroxides, and having intercalated therein a pharmaceutically-active compound having at least one anionic group; and

a non-toxic compound comprising an anion configured to intercalate between the layers in the layered double hydroxide in preference to the pharmaceutically-active compound and release the pharmaceutically-active compound in the subject's stomach by displacing the pharmaceutically-active compound from the layers in the layered double hydroxide.

2. The method according to claim 1 , wherein the layered double hydroxide, before intercalation, is represented by the general formula:

[M II (1-x) M III x (OH) 2 ] x+ [A n− x/n ]

wherein:

M II is a divalent metal cation;

M III a trivalent metal cation;

A is a displaceable anion;

n is an integer; and

x is a positive number less than 1, which compound is optionally hydrated with a stoichiometric amount or a non-stoichiometric amount of water.

3. The method according to claim 2 , wherein M II is Mg or Ca and M III is Al.

4. The method according to claim 2 , wherein A is selected from the group consisting of OH, F, Cl, Br, I, SO 4 , and NO 3 .

5. The method according to claim 1 , wherein the layered double hydroxide, before intercalation, is represented by the general formula:

[M I M III 2 (OH) 6 ] + [A n− 1/n ]

wherein:

M I is a monovalent metal cation;

M III a trivalent metal cation;

A is a displaceable anion; and

n is an integer, which compound is optionally hydrated with a stoichiometric or non-stoichiometric amount of water.

6. The method according to claim 5 , wherein M I is Li and M III is Al.

7. The method according to claim 5 , wherein A is selected from the group consisting of OH, F, Cl, Br, I, SO 4 , and NO 3 .

8. The method according to claim 7 , wherein the layered double hydroxide is [LiAl 2 (OH)] 6 Cl.H 2 O.

9. The method according to claim 1 , wherein the pharmaceutically-active compound is a pharmaceutically-active compound containing at least one carboxylic acid group or a non-toxic salt thereof.

10. The method according to claim 1 , wherein the intercalate further comprises a non-toxic compound having an anion which is capable of displacing the pharmaceutically-active compound from the intercalate.

11. The method according to claim 10 , wherein the non-toxic compound is selected from the group consisting of magnesium carbonate, magnesium hydrogen carbonate, calcium carbonate or calcium hydrogen carbonate.

12. The method according to claim 1 , wherein the pharmaceutically-active compound is selected from the group consisting of 4-biphenylacetic acid, Diclofenac, Gemfibrozil, Ibuprofen, Naproxen, 2-propylpentanoic acid and Tolfenamic acid.

13. The method according to claim 1 , wherein the intercalate is configured to release the pharmaceutically-active compound in a controlled manner over a period of time.

14. The method according to claim 13 , wherein the period of time is 120 minutes or less.

15. The method according to claim 1 , wherein the drug delivery system is an oral dosage unit.

16. The method according to claim 1 , wherein the drug delivery system comprises a buffer.

17. The method according to claim 16 , wherein the buffer comprises a phosphate buffer.

18. The method according to claim 1 , wherein the anion of the non-toxic compound is a carbonate anion or a hydrogen carbonate anion.

19. The method according to claim 1 , wherein the anion of the non-toxic compound is an anion which intercalates more strongly than a carbonate anion.

20. The method according to claim 1 , wherein the anion of the non-toxic compound is an anion which intercalates less strongly than a carbonate anion.