Drug release 
724
—
TEST 1—
If the product complies with this test, the labeling indicates that it meets USP
Drug Release Test 1.
Medium:
dilute hydrochloric acid (7 in 1000); 800 mL.
Apparatus 1:
100 rpm.
Times:
15, 45, 90, and 120 minutes.
Procedure—
At each Time, withdraw 8.0 mL of the solution under test, and pass through a filter having a 35-µm or finer porosity. Using the filtrate as the Assay preparation, suitably diluted with Medium if necessary, and using Medium to prepare the Standard preparation, determine the amount of Li2CO3 dissolved by employing a flame photometer, as directed in the Assay.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 1.
| Time (minutes) |
 Amount dissolved |
| 15 |
between 2% and 16% |
| 45 |
between 25% and 45% |
| 90 |
between 60% and 85% |
| 120 |
not less than 85% |
TEST 2—
If the product complies with this test, the labeling indicates that it meets USP
Drug Release Test 2.
Apparatus and Procedure—
Proceed as directed for Test 1.
Medium:
water; 900 mL.
Times:
1, 3, and 7 hours.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 1.
| Time (hours) |
Amount dissolved |
| 1 |
not more than 40% |
| 3 |
between 45% and 75% |
| 7 |
not less than 70% |
TEST 3—
If the product complies with this test, the labeling indicates that it meets USP
Drug Release Test 3.
Medium:
water; 250 mL.
Apparatus 3:
6 dips per minute, 20-mesh top screen and 100-mesh bottom screen.
Procedure—
Proceed as directed for Test 1.
Times and Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 1.
| Time (hours) |
Amount dissolved |
| 1 |
between 10% and 45% |
| 2 |
between 25% and 75% |
| 6 |
not less than 70% |
TEST 4—
If the product complies with this test, the labeling indicates that it meets USP
Drug Release Test 4.
Medium, Apparatus, Times, and Procedure—
Proceed as directed for Test 1.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 1.
| Time (minutes) |
Amount dissolved |
| 15 |
between 2% and 16% |
| 45 |
between 25% and 45% |
| 90 |
between 60% and 85% |
| 120 |
not less than 80% |
Dissolution 711—
TEST 1—
If the product complies with this test, the labeling indicates that it meets USP
Dissolution Test 1.
Medium:
dilute hydrochloric acid (7 in 1000); 800 mL.
Apparatus 1:
100 rpm.
Times:
15, 45, 90, and 120 minutes.
Procedure—
At each Time, withdraw 8.0 mL of the solution under test, and pass through a filter having a 35-µm or finer porosity. Using the filtrate as the Assay preparation, suitably diluted with Medium if necessary, and using Medium to prepare the Standard preparation, determine the amount of Li2CO3 dissolved by employing a flame photometer, as directed in the Assay.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 2.
| Time (minutes) |
Amount dissolved |
| 15 |
between 2% and 16% |
| 45 |
between 25% and 45% |
| 90 |
between 60% and 85% |
| 120 |
not less than 85% |
TEST 2—
If the product complies with this test, the labeling indicates that it meets USP
Dissolution Test 2.
Apparatus and Procedure—
Proceed as directed for Test 1.
Medium:
water; 900 mL.
Times:
1, 3, and 7 hours.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 2.
| Time (hours) |
Amount dissolved |
| 1 |
not more than 40% |
| 3 |
between 45% and 75% |
| 7 |
not less than 70% |
TEST 3—
If the product complies with this test, the labeling indicates that it meets USP
Dissolution Test 3.
Medium:
water; 250 mL.
Apparatus 3:
6 dips per minute, 20-mesh top screen and 100-mesh bottom screen.
Procedure—
Proceed as directed for Test 1.
Times and Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 2.
| Time (hours) |
Amount dissolved |
| 1 |
between 10% and 45% |
| 2 |
between 25% and 75% |
| 6 |
not less than 70% |
TEST 4—
If the product complies with this test, the labeling indicates that it meets USP
Dissolution Test 4.
Medium, Apparatus, Times, and Procedure—
Proceed as directed for Test 1.
Tolerances—
The percentages of the labeled amount of Li
2CO
3 dissolved at the specified times conform to
Acceptance Table 2.
| Time (minutes) |
Amount dissolved |
| 15 |
between 2% and 16% |
| 45 |
between 25% and 45% |
| 90 |
between 60% and 85% |
| 120 |
not less than 80% |
(Official April 1, 2006)
Assay—
[NOTE—The
Standard preparation and the
Assay preparation may be diluted quantitatively with
Dilute hydrochloric acid (1 in 200), if necessary, to yield solutions of suitable concentrations adaptable to the linear or working range of the instrument.
]
Dilute hydrochloric acid
(1 in 200)—Dilute 5 mL of hydrochloric acid with water to obtain 1000 mL of solution.
Standard preparation—
Transfer to a 100-mL volumetric flask about 30 mg of
USP Lithium Carbonate RS, accurately weighed. Add about 20 mL of water and 0.5 mL of hydrochloric acid, shake until dissolved, dilute with water to volume, and mix to obtain a solution having a known concentration of about 300 µg of
USP Lithium Carbonate RS per mL.
Assay preparation—
Transfer an accurately counted number of Tablets, equivalent to about 1200 mg of lithium carbonate, to a 250-mL screw-capped flask. Add 100.0 mL of Dilute hydrochloric acid (1 in 200), shake until the Tablets dissolve, and filter, discarding the first 25 mL of the filtrate. Transfer 5.0 mL of the filtrate to a 200-mL volumetric flask, dilute with Dilute hydrochloric acid (1 in 200) to volume, and mix.
Procedure—
Employ a suitable flame photometer, and adjust the instrument with
Dilute hydrochloric acid (1 in 200). Aspirate the
Standard preparation and the
Assay preparation into the instrument, in turn, and measure the emission at about 671 nm. Calculate the quantity, in mg, of lithium carbonate (Li
2CO
3) in each Tablet taken by the formula:
L(C/D)(A/S),
in which
C is the concentration, in µg per mL, of
USP Lithium Carbonate RS in the
Standard preparation; L is the labeled quantity, in mg, of lithium carbonate in each Tablet;
D is the concentration, in µg per mL, of lithium carbonate in the
Assay preparation, based on the number of Tablets taken, the labeled amount, in mg, of lithium carbonate per Tablet, and the extent of dilution; and
A and
S are the photometric readings of the
Assay preparation and the
Standard preparation, respectively.
