Lithium Carbonate Extended-Release Tablets
»Lithium Carbonate Extended-Release Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of lithium carbonate (Li2CO3).
Packaging and storage— Preserve in well-closed containers.
Labeling— The labeling indicates the Drug Release Testwith which the product complies.
Identification— Aportion of powdered Tablets responds to the Identificationtests under Lithium Carbonate.
Uniformity of dosage units á905ñ: meet the requirements.
Drug release á724ñ—
TEST1— If the product complies with this test,the labeling indicates that it meets USPDrug 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 Li2CO3dissolved 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 USPDrug 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 Li2CO3dissolved 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 USPDrug 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 Li2CO3dissolved 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 USPDrug Release Test 4.
Medium,Apparatus,Times,and Procedure— Proceed as directed for Test 1.
Tolerances— The percentages of the labeled amount of Li2CO3dissolved 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 (Li2CO3)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.
Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1142
Pharmacopeial Forum:Volume No.29(6)Page 1917
Phone Number:1-301-816-8330