Packaging and storage—
Preserve in well-closed containers.
Labeling—
Label the Tablets to indicate that they are to be chewed before being swallowed.
Identification—
A:
Transfer a quantity of powdered Tablets, equivalent to about 2 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 with three more 60-mL portions of water. Transfer the residue to a 250-mL beaker, and heat on a steam bath to dryness: the residue so obtained meets the requirements of the Identification tests under Magaldrate.
Microbial limits 
61
—
Tablets meet the requirements of the test for absence of
Escherichia coli.
Acid-neutralizing capacity—
Proceed as directed under
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—
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 quantity of finely powdered Tablets, 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
, and proceed as directed in the test for
Defoaming activity under
Magaldrate and Simethicone Oral Suspension, beginning with “Cap the jar.” Record the time, in seconds, for the foam to collapse to the extent that its thickness, measured from the surface of the liquid, is 1.0 cm. The defoaming activity time does not exceed 45 seconds.
Magnesium hydroxide content—
Test preparation—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 1 g of magaldrate, to a 100-mL volumetric flask, add 30 mL of dilute hydrochloric acid (1 in 10), shake for 15 minutes, 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.” 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.
Assay for magaldrate—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 6 g of magaldrate, to a 200-mL volumetric flask. Add 100.0 mL of 2 N hydrochloric acid VS, and swirl by mechanical means for 30 minutes. Dilute with water to volume, mix, and filter. Transfer 100.0 mL of the filtrate to a beaker. 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 2 N hydrochloric acid is equivalent to 70.80 mg of Al
5Mg
10(OH)
31(SO
4)
2.
Assay for polydimethylsiloxane—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 20 mg of simethicone, to a 60-mL separator. Add 10.0 mL of hexanes and 25 mL of 6 N hydrochloric acid, cap the separator, and shake by mechanical means for not less than 2 hours. Allow to stand for about 10 minutes, and drain off as much of the lower, aqueous layer as possible without removing any of the unseparated interphase. Add 25 mL of 4 N sodium hydroxide to the separator, cap it, and shake by mechanical means for 1 hour. Transfer the mixture from the separator to a 50-mL centrifuge tube, cap, and centrifuge to obtain clear layers. Transfer not less than 5 mL of the clear upper hexanes layer to a test tube containing about 0.5 g of anhydrous sodium sulfate. Cap the tube, shake vigorously, and allow to stand to obtain a clear supernatant (
Assay preparation). Prepare three
Standard preparations in hexanes having known concentrations of about 1.6, 2.0, and 2.4 mg of
USP Polydimethylsiloxane RS per mL, respectively. Concomitantly determine the absorbances of the
Assay preparation and the
Standard preparations in a 0.5-mm cell at the wavelength of maximum absorbance at about 1260 cm
–1 with an IR spectrophotometer, using hexanes as the blank.
[NOTE—Between each measurement, rinse the cell with heptane, empty, and dry it.
] Plot the absorbances for the
Standard preparations versus concentration, in mg per mL, of
USP Polydimethylsiloxane RS, and draw the straight line best fitting the three plotted points. From the graph so obtained, determine the concentration,
C, in mg per mL, of polydimethylsiloxane in the
Assay preparation. Calculate the quantity, in mg, of [–(CH
3)
2SiO–]
n in the portion of Tablets taken by multiplying
C by 10.
