There is provided use of a mixed metal compound in the manufacture of medicament for neutralising or buffering stomach acid, wherein the mixed metal compound contains at least one trivalent metal selected from iron (III) and aluminium and at least one divalent metal selected from of magnesium, iron, zinc, calcium, lanthanum and cerium, wherein (A) the mixed metal compound is of formula (I) : M II 1-a M III a O b A n- c. zH 2 O (I) where M" is the at least one bivalent metal; M III is the at least one trivalent metal; A n- is at least one n-valent anion; 2+a = 2b+n and n < 0.9a, and z is 2 or less, and/or (B) the mixed metal compound is provided in the form of a granular material comprising (i) at least 50% by weight, based on the weight of the granular material, of the mixed metal compound (ii) from 3 to 12% by weight, based on the weight of the granular material, of non-chemically bound water, and (iii) no greater than 47% by weight based on the weight of the granular material of excipient.