Alumina and Magnesium Trisilicate Oral Suspension
» Alumina and Magnesium Trisilicate Oral Suspension contains the equivalent of not less than 90.0 percent and not more than 110.0 percent of the labeled amounts of aluminum hydroxide [Al(OH)3] and magnesium trisilicate (Mg2Si3O8).
Packaging and storage— Preserve in tight containers.
Identification—
A: To a mixture of 5 mL in 10 mL of 3 N hydrochloric acid add 5 drops of methyl red TS, heat to boiling, add 6 N ammonium hydroxide until the color of the solution changes to deep yellow, then continue boiling for 2 minutes, and filter: the filtrate responds to the tests for Magnesium 191.
B: Wash the solids on the filter obtained in Identification test A with hot ammonium chloride solution (1 in 50), add 10 mL of 3 N hydrochloric acid, and filter: the filtrate responds to the tests for Aluminum 191.
C: Transfer the filter paper and contents from Identification test B to a small platinum dish, ignite, cool in a desiccator, and weigh. Moisten the residue with water and add 6 mL of hydrofluoric acid. Evaporate to dryness, ignite for 5 minutes, cool in a desiccator, and weigh: a loss of more than 10% in relation to the weight of the residue from the initial ignition indicates SiO2.
Acid-neutralizing capacity 301— Not less than 5 mEq of acid is consumed by the minimum single dose recommended in the labeling.
pH 791: between 7.5 and 8.5.
Assay for aluminum hydroxide—
Edetate disodium titrant— Prepare and standardize as directed in the Assay under Ammonium Alum.
Assay preparation— Transfer about 10 g of well-shaken Oral Suspension to a tared beaker, and weigh accurately. Add 50 mL of water and 10 mL of hydrochloric acid, and digest on a steam bath for 1 hour. Cool, and filter into a 200-mL volumetric flask, washing the filter with water into the flask. Dilute with water to volume, and mix.
Procedure— Pipet 20 mL of Assay preparation into a 250-mL beaker, add 20 mL of water, then add, in the order named and with continuous stirring, 25.0 mL of Edetate disodium titrant and 20 mL of acetic acid–ammonium acetate buffer TS, and heat near the boiling point for 5 minutes. Cool, add 50 mL of alcohol and 2 mL of dithizone TS, and mix. Titrate with 0.05 M zinc sulfate VS until the color changes from green-violet to rose-pink. Perform a blank determination, substituting 20 mL of water for the Assay preparation, and make any necessary correction. Each mL of 0.05 M Edetate disodium titrant consumed is equivalent to 3.900 mg of Al(OH)3.
Assay for magnesium trisilicate—
Assay preparation— Prepare as directed in the Assay for aluminum hydroxide.
Procedure— Pipet 20 mL of Assay preparation into a 400-mL beaker, add 180 mL of water and 20 mL of triethanolamine, and stir. Add 10 mL of ammonia–ammonium chloride buffer TS and 3 drops of an eriochrome black indicator solution prepared by dissolving 200 mg of eriochrome black T in a mixture of 15 mL of triethanolamine and 5 mL of dehydrated alcohol, and mix. Cool the solution to between 3 and 4 by immersion of the beaker in an ice bath, then remove and titrate with 0.05 M edetate disodium VS to a blue endpoint. Perform a blank determination, substituting 20 mL of water for the Assay preparation, and make any necessary correction. Each mL of 0.05 M edetate disodium consumed is equivalent to 6.521 mg of Mg2Si3O8.
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Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Principal Scientific Liaison
1-301-816-8251		 (SM32010) Monographs - Small Molecules 3
USP35–NF30 Page 2125