Packaging and storage—
Preserve in tight containers.
Identification—
A:
Dissolve an amount of Oral Suspension, equivalent to about 800 mg of magaldrate, in 20 mL of 3 N hydrochloric acid, dilute with water to about 50 mL, add 3 drops of
methyl red TS, and proceed as directed in
Identification test
A under
Magaldrate, beginning with “and heat to boiling.”
B:
It responds to
Identification test
B under
Magaldrate.
C:
Transfer an amount of Oral Suspension, equivalent to about 1 g of magaldrate, to a 100-mL centrifuge tube. Add about 60 mL of water, cap, and shake for 3 minutes. Centrifuge the suspension, and discard the supernatant. Repeat the washing of the residue with three 60-mL portions of water. Transfer the residue to a 250-mL beaker, and heat on a steam bath to dryness: the X-ray diffraction pattern (see
X-ray Diffraction 
941
), in the d-spacings region below 2.57 angstrom units, of the residue so obtained conforms to that of
USP Magaldrate RS.
Microbial limits 61—
Its total aerobic microbial count does not exceed 100 cfu per mL, and it meets the requirements of the test for absence of
Escherichia coli.
Acid-neutralizing capacity 301—
The acid consumed by the minimum single dose recommended in the labeling is not less than 5 mEq, and not less than the number of mEq calculated by the formula:
0.8(0.0282M),
in which 0.0282 is the theoretical acid-neutralizing capacity, in mEq per mg, of magaldrate, and
M is the quantity, in mg, of the labeled amount of magaldrate.
Magnesium hydroxide content—
Test preparation—
Transfer an accurately measured quantity of Oral Suspension, equivalent to about 1 g of magaldrate, to a 100-mL volumetric flask, add 30 mL of dilute hydrochloric acid (1 in 10), shake to dissolve, dilute with water to volume, and mix.
Procedure—
Transfer 10.0 mL of
Test preparation to a 400-mL beaker, and proceed as directed in the test for
Magnesium hydroxide content under
Magaldrate, beginning with “and dilute with water to about 200 mL.” Not less than 492 mg and not more than 666 mg of magnesium hydroxide [Mg(OH)
2] per g of the labeled amount of magaldrate is found.
Aluminum hydroxide content—
Edetate disodium titrant—
Prepare and standardize as directed in the
Assay under
Ammonium Alum.
Test preparation—
Prepare as directed in the test for Magnesium hydroxide content.
Procedure—
Transfer 10.0 mL of
Test preparation and 20 mL of water to a 250-mL beaker, and proceed as directed for
Procedure in the test for
Aluminum hydroxide content under
Magaldrate, beginning with “Add, with stirring, 25.0 mL of
Edetate disodium titrant.” Not less than 321 mg and not more than 459 mg of aluminum hydroxide [Al(OH)
3] per g of the labeled amount of magaldrate is found.
Other requirements—
Evaporate a volume of Oral Suspension, equivalent to about 5 g of magaldrate, on a steam bath to dryness: the residue so obtained meets the requirements of the tests for
Arsenic and
Heavy metals under
Magaldrate.
Assay—
Transfer an accurately measured quantity of Oral Suspension, equivalent to about 3 g of magaldrate, to a beaker. Add 100.0 mL of 1 N hydrochloric acid VS, and mix, using a magnetic stirrer to achieve dissolution. Titrate the excess acid with 1 N sodium hydroxide VS to a pH of 3.0, determined potentiometrically. Perform a blank determination (see
Residual Titrations under
Titrimetry 541). Each mL of 1 N hydrochloric acid is equivalent to 35.40 mg of Al
5Mg
10(OH)
31(SO
4)
2.
