Packaging and storage—
Preserve in tight containers, and keep from freezing.
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:
Wash the precipitate obtained in
Identification test
A with hot ammonium chloride solution (1 in 50), and dissolve the precipitate in hydrochloric acid. Divide this solution into two portions: the dropwise addition of 6 N ammonium hydroxide to one portion yields a gelatinous white precipitate, which does not dissolve in an excess of 6 N ammonium hydroxide. The dropwise addition of 1 N sodium hydroxide to the other portion yields a gelatinous white precipitate, which dissolves in an excess of 1 N sodium hydroxide, leaving some turbidity.
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, insert the 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.
D:
The IR absorption spectrum, in the 7- to 15-µm region, determined in a 0.1-mm cell, of the
Assay preparation prepared as directed in the
Assay for polydimethylsiloxane exhibits maxima only at the same wavelengths as that of the
Standard preparation prepared as directed in the
Assay for polydimethylsiloxane.
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.
Defoaming activity—
Foaming solution—
Dissolve 5 mg of FD&C Blue No. 1 and 10 g of polyoxyethylene (23) lauryl ether in 1000 mL of water. Warm to 37
before use.
Procedure—
[NOTE—For each test use a clean 250-mL cylindrical jar (50-mm internal diameter × 110-mm internal height) with a 50-mm opening fitted with a tight cap with an inert liner.
] Transfer a volume of well-mixed Oral Suspension, equivalent to 20 mg of simethicone, to a 250-mL cylindrical jar containing 50 mL of 0.6 N hydrochloric acid that has been warmed to 37
. Cap the jar, and clamp it in an upright position on a wrist-action shaker. Employing a radius of 13.3 ± 0.4 cm (measured from the center of shaft to center of bottle), shake for 30 seconds through an arc of 10 degrees at a frequency of 300 ± 30 strokes per minute. Uncap the jar, add 50 mL of
Foaming solution, recap the jar, and shake for 10 seconds using the conditions specified above. Record the time required for the foam to collapse. The time, in seconds, for foam collapse is determined at the instant the first portion of foam-free liquid surface appears, measured from the end of the shaking period. The defoaming activity time does not exceed 45 seconds.
System suitability tests—
[NOTE—For each of the following tests use a separate clean 250-mL cylindrical jar having the dimensions specified for
Procedure.
] Transfer 50 mL of
Foaming solution to a 250-mL cylindrical jar containing 50 mL of 0.6 N hydrochloric acid that has been warmed to 37
. Cap the jar, and shake it for 10 seconds using the conditions specified for
Procedure: the foam layer remains intact for not less than 5 minutes. Transfer 0.15 mL of simethicone and 50 mL of
Foaming solution to a second 250-mL cylindrical jar containing 50 mL of 0.6 N hydrochloric acid that has been warmed to 37
. Cap the jar, and shake it for 10 seconds using the conditions specified for
Procedure: the time required for the foam to collapse does not exceed 45 seconds.
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.
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 for magaldrate—
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 magaldrate [Al
5Mg
10(OH)
31(SO
4)
2].
Assay for polydimethylsiloxane—
Transfer an accurately measured quantity of Oral Suspension, equivalent to about 250 mg of simethicone, to a 200-mL centrifuge bottle. Add an equal volume of hydrochloric acid, swirl to dissolve the Oral Suspension, add 25.0 mL of hexanes, and immediately close the bottle securely with a cap having an inert liner. Shake the bottle for 30 minutes, and centrifuge the mixture until a clear supernatant layer is obtained (
Assay preparation). Prepare a
Standard preparation of
USP Polydimethylsiloxane RS in hexanes having a known concentration of about 10 mg per mL. Concomitantly determine the absorbances of the
Assay preparation and the
Standard preparation in 0.1-mm cells at the wavelength of maximum absorbance at about 7.9 µm and at the wavelengths of minimum absorbance at about 7.5 µm and 8.3 µm, with a suitable IR spectrophotometer, using hexanes as the blank. Draw a linear baseline between the two minima, and determine the absorbances for the
Standard preparation and the
Assay preparation with respect to the baseline, making any necessary correction for the blank. Calculate the quantity, in mg, of [–(CH
3)
2SiO–]
n in the portion of Oral Suspension taken by the formula:
25C(AU / AS),
in which
C is the concentration, in mg per mL, of
USP Polydimethylsiloxane RS in the
Standard preparation; and
AU and
AS are the absorbances of the
Assay preparation and the
Standard preparation, respectively.
