Drug release á724ñ—
TEST1—
If the product complies with this test,the labeling indicates that it meets USP
Drug Release Test 1.
Medium:
dilute hydrochloric acid (7in 1000);800mL.
Apparatus 1:
100rpm.
Times:
15,45,90,and 120minutes.
Procedure—
At each Time,withdraw 8.0mLof 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 Dissolution Medium if necessary,and using Dissolution Medium to prepare the Standard preparation,determine the amount of Li2CO3dissolved by employing a flame photometer,as directed in the Assay.
Tolerances—
The percentages of the labeled amount of Li
2CO
3dissolved 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% |
TEST2—
If the product complies with this test,the labeling indicates that it meets USP
Drug Release Test 2.
ApparatusandProcedure—
Proceed as directed for Test 1.
Medium:
water;900mL.
Times:
1,3,and 7hours.
Tolerances—
The percentages of the labeled amount of Li
2CO
3dissolved 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% |
TEST3—
If the product complies with this test,the labeling indicates that it meets USP
Drug Release Test 3.
Medium:
water;250mL.
Apparatus 3:
6dips per minute,20-mesh top screen and 100-mesh bottom screen.
Procedure—
Proceed as directed for Test 1.
Timesand Tolerances—
The percentages of the labeled amount of Li
2CO
3dissolved 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% |
TEST4—
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
3dissolved 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% |
Assay—
[NOTE—The
Standard preparation and the
Assay preparation may be diluted quantitatively with
Dilute hydrochloric acid (1in 200),if necessary,to yield solutions of suitable concentrations adaptable to the linear or working range of the instrument.
]
Dilute hydrochloric acid
(1in 200)—Dilute 5mLof hydrochloric acid with water to obtain 1000mLof solution.
Standard preparation—
Transfer to a 100-mLvolumetric flask about 30mg of
USP Lithium Carbonate RS,accurately weighed.Add about 20mLof water and 0.5mLof hydrochloric acid,shake until dissolved,dilute with water to volume,and mix to obtain a solution having a known concentration of about 300µg of
USP Lithium Carbonate RSper mL.
Assay preparation—
Transfer an accurately counted number of Tablets,equivalent to about 1200mg of lithium carbonate,to a 250-mLscrew-capped flask.Add 100.0mLof Dilute hydrochloric acid(1in 200),shake until the Tablets dissolve,and filter,discarding the first 25mLof the filtrate.Transfer 5.0mLof the filtrate to a 200-mLvolumetric flask,dilute with Dilute hydrochloric acid(1in 200)to volume,and mix.
Procedure—
Employ a suitable flame photometer,and adjust the instrument with
Dilute hydrochloric acid(1in 200).Aspirate the
Standard preparationand the
Assay preparationinto the instrument,in turn,and measure the emission at about 671nm.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
Cis the concentration,in µg per mL,of
USP Lithium Carbonate RSin the
Standard preparation;Lis the labeled quantity,in mg,of lithium carbonate in each Tablet;
Dis 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
Aand
Sare the photometric readings of the
Assay preparationand the
Standard preparation,respectively.