Metal compounds, mixed or sulphated, as phosphate binders
A mixed metal compound for pharmaceutical use is free from aluminium and has a phosphate binding capacity of at least 30%, by weight of the total weight of phosphate present, over a pH range of from 2-8. The compound is especially useful for treatment of hyperphosphataemia. The metals are preferably iron (III) and at least one of calcium, magnesium, lanthanum and cerium. A metal sulphate for pharmaceutical use is selected from at least one of calcium, lanthanum and cerium sulphate compounds and has a phosphate binding capacity of at least 30% by weight of the total phosphate present, over a pH range from 2-8.
1. A method for treating hyperphosphataemia, in an animal in need thereof, which comprises administering to said animal, a therapeutically effective amount of a phosphate-binding, mixed metal compound which is free of aluminium and contains iron (III) and at least one additional metal M selected from magnesium, calcium, lanthanum and cerium.
2. A method as claimed in claim 1 in which said compound has a phosphate binding capacity of at least 30% by weight of total phosphate present, as measured by any of the following methods (1) or (2), over a pH range of 3 to 7;
(1) adding 1 gram of said mixed metal compound to 25 ml of 40 mmol 1 −1 sodium phosphate buffer solution, homogenizing and gently agitating at room temperature for 30 minutes, centrifuging at 3000 rpm for 5 minutes, filtering through 0.22 μm millipore filter and measuring the soluble phosphate in the supernatant thus produced;
(2) adding 1 gram of said mixed metal compound to 25 ml of 20 mmol 1 −1 sodium phosphate buffer solution, homogenizing and gently agitating at room temperature for 30 minutes, centrifuging at 3000 rpm for 5 minutes, filtering through 0.22 μm millipore filter and measuring the soluble phosphate in the supernatant thus produced.
3. A method as claimed in claim 1 in which said metal compound contains hydroxyl and/or carbonate ions.
4. A method as claimed in claim 2 in which said compound has a phosphate binding capacity of at least 30% by weight of the total weight of phosphate present as measured by method (1) or by method (2) over a pH range of 2 to 8.
5. A method as claimed in claim 1 in which the ratio M:Fe for the compound is at least 1.1:1.
6. A method as claimed in claim 1 in which the ratio M:Fe for the compound is at least 1.3:1.
7. A method as claimed in claim 1 in which the ratio M:Fe for the compound is at least 1.7:1.
8. A method as claimed in claim 1 in which the ratio M:Fe for the compound is up to 5:1.
9. A method as claimed in claim 1 in which the ratio M:Fe for the compound is up to 2.6:1.
10. A method as claimed in claim 1 in which the ratio M:Fe for the compound is up to 2.4:1.
11. A method as claimed in claim 1 in which the additional metal is calcium.
12. A method as claimed in claim 1 in which the additional metal is magnesium.
13. A method as claimed in claim 1 in which the compound additionally contains at least one of sulphate, chloride and oxide.
14. A method as claimed in claim 1 , in which the compound is obtained as precipitate from a solution of a mixture of metallic salts.
15. The method of claim 14 , wherein the precipitate is unaged.
16. The method of claim 14 , wherein the precipitate is washed and unaged.