Co-magaldrox Tablets
Action and use
Antacid.
Definition
Co-magaldrox Tablets contain Magnesium Hydroxide and Dried Aluminium Hydroxide. The amount of Dried Aluminium Hydroxide is adjusted to give the required content of Al2O3.
Content of magnesium hydroxide, Mg(OH)2
90.0 to 110.0% of the stated amount.
Content of Al2O3
45.0 to 55.0% of the stated amount of dried aluminium hydroxide.
Identification
Assay
For Al2O3
Weigh and powder 20 tablets. To a quantity of the powdered tablets containing 1.5 g of dried aluminium hydroxide add 20 mL of water, stir and slowly add 30 mL of 3m hydrochloric acid. Heat gently, if necessary, to aid solution, cool, filter, wash the filter well with water, dilute the combined filtrate and washings to 200 mL with water and mix. Reserve a portion of the solution for the Assay for magnesium hydroxide. To 10 mL add 20 mL of water and, with continuous stirring, 25 mL of 0.05m disodium edetate VS followed by 20 mL of a mixture of equal volumes of 2m ammonium acetate and 2m acetic acid. Heat near the boiling point for 5 minutes, cool, add 50 mL of absolute ethanol and 3 mL of a freshly prepared 0.025% w/v solution of dithizone in absolute ethanol. Titrate the excess of disodium edetate with 0.05m zinc sulfate VS until the colour of the solution changes from greenish blue to reddish violet. Each mL of 0.05m disodium edetate VS is equivalent to 2.549 mg of Al2O3.
For magnesium hydroxide
To a volume of the solution reserved in the Assay for Al2O3 containing about 40 mg of magnesium hydroxide add 200 mL of water and 20 mL of triethanolamine and stir. Add 10 mL of ammonia buffer pH 10.9 and cool the solution to between 3° and 4° by immersion in iced water. Titrate the cooled solution with 0.05m disodium edetate VS using mordant black 11 solution as indicator. Each mL of 0.05m disodium edetate VS is equivalent to 2.916 mg of Mg(OH)2.