Lamivudine and Zidovudine Tablets
DEFINITION
Lamivudine and Zidovudine Tablets contains NLT 90.0% and NMT 110.0% of the labeled amount of lamivudine (C8H11N3O3S) and zidovudine (C10H13N5O4).
IDENTIFICATION
•  The retention times of the lamivudine and zidovudine peaks of the Sample solution correspond to those of the Standard solution, as obtained in the Assay.
ASSAY
•  Procedure
Solution A:  25 mM of ammonium acetate. Adjust with glacial acetic acid to a pH of 4.0.
Solution B:  Methanol
Solution C:  Acetonitrile
Mobile phase:  See Table 1.
Table 1
Time
(min)
Solution A
(%)
Solution B
(%)
Solution C
(%)
0 95 5 0
15.0 95 5 0
30.0 70 30 0
38.0 70 30 0
38.1 0 0 100
45.0 0 0 100
45.1 95 5 0
60.0 95 5 0
Diluent:  Solution A and Solution B (19:1)
System suitability solution:  0.17 mg/mL of USP Lamivudine Resolution Mixture B RS in Diluent
Standard solution:  0.15 mg/mL of USP Lamivudine RS and 0.30 mg/mL of USP Zidovudine RS in Diluent
Sample stock solution:  Transfer a counted number of Tablets, equivalent to 1500 mg of zidovudine and 750 mg of lamivudine, into a 500-mL volumetric flask. Add 250 mL of water, and disintegrate completely by shaking for a minimum of 15 min. Dilute with water to volume, and mix.
Sample solution:  Pass a portion of the Sample stock solution through a filter of 0.45-µm pore size, discarding the first 2–3 mL. Further dilute the filtrate to obtain 0.15 mg/mL of lamivudine and 0.30 mg/mL of zidovudine in Diluent.
Chromatographic system 
Mode:  LC
Detector:  UV 270 nm
Column:  3-mm × 25-cm; packing L1
Flow rate:  0.5 mL/min
Injection size:  10 µL
System suitability 
Samples:  System suitability solution and Standard solution [Note—The relative retention times for lamivudine diastereomer and lamivudine are 0.50 and 0.52, respectively. ]
Suitability requirements 
Resolution:  NLT 1.5 between lamivudine diastereomer and lamivudine, System suitability solution
Relative standard deviation:  NMT 2.0% for zidovudine and lamivudine, Standard solution
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of the labeled amount of lamivudine (C8H11N3O3S) and zidovudine (C10H13N5O4) in the portion of Tablets taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response of zidovudine or lamivudine from the Sample solution
rS== peak response of zidovudine or lamivudine from the Standard solution
CS== concentration of USP Zidovudine RS or USP Lamivudine RS in the Standard solution (mg/mL)
CU== nominal concentration of zidovudine or lamivudine in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0%
PERFORMANCE TESTS
•  Dissolution 711
Test 1 
Medium:  0.1 N hydrochloric acid; 900 mL, deaerated
Apparatus 2:  75 rpm
Time:  15 min
Lamivudine response factor solutions:  0.167 mg/mL of USP Lamivudine RS in Medium. [Note—Prepare in duplicate. ]
Zidovudine response factor solutions:  0.333 mg/mL of USP Zidovudine RS in Medium. [Note—Prepare in duplicate. ]
Sample solution:  Pass a portion of the solution under test through a suitable filter (PTFE, PVDF, or equivalent) of 0.45-µm pore size.
Detector:  UV 240–300 nm
Blank:  Medium
Cell length:  0.02-cm flowcell
Analysis:  The calculations of the percentages dissolved are done using a multicomponent analysis software.
Tolerances:  NLT 85% (Q) of the labeled amount of zidovudine and lamivudine is dissolved.
Test 2:  If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.
Medium:  0.1 N hydrochloric acid; 900 mL
Apparatus 2:  75 rpm
Time:  30 min
Buffer solution:  7.7 g/L of ammonium acetate in water
Mobile phase:  Acetonitrile and Buffer solution (1:9)
Standard stock solution:  1.4 mg/mL of USP Lamivudine RS and 2.8 mg/mL of USP Zidovudine RS in Medium. A small amount of methanol, NMT 20% of the final volume, can be used to dissolve both compounds.
Standard solution:  0.168 mg/mL of lamivudine and 0.336 mg/mL of zidovudine in Medium, from the Standard stock solution
Sample solution:  Pass a portion of the solution under test through a suitable filter.
Chromatographic system 
Mode:  LC
Detector:  UV 270 nm
Column:  4.6-mm × 15-cm; packing L1
Column temperature:  40
Flow rate:  1.2 mL/min
Injection size:  10 µL
System suitability 
Sample:  Standard solution
Suitability requirements 
Column efficiency:  NLT 1500 theoretical plates for lamivudine and NLT 3000 theoretical plates for zidovudine
Tailing factor:  NMT 2.0 for lamivudine and zidovudine
Relative standard deviation:  NMT 2.0% for zidovudine and lamivudine
Calculate the percentages of lamivudine (C8H11N3O3S) and zidovudine (C10H13N5O4) dissolved:
Result = (rU/rS) × (CS/L) × V × 100
rU== peak response for lamivudine or zidovudine from the Sample solution
rS== peak response for lamivudine or zidovudine from the Standard solution
CS== concentration of lamivudine or zidovudine in the Standard solution (mg/mL)
L== label claim for lamivudine or zidovudine (mg/Tablet)
V== volume of Medium, 900 mL
Tolerances:  NLT 80% (Q) of the labeled amount of zidovudine and lamivudine is dissolved.
•  Uniformity of Dosage Units 905: Meet the requirements for zidovudine and lamivudine
IMPURITIES
•  Organic Impurities
Solution A, Solution B, Solution C, Mobile phase, Diluent, System suitability solution, Sample solution, Chromatographic system, and System suitability:  Proceed as directed in the Assay.
Analysis 
Sample:  Sample solution
Calculate the percentage of each lamivudine related impurity in the portion of Tablets taken:
Result = (rU/rT) × 100
rU== peak response of each individual impurity from the Sample solution
rT== sum of the peak responses of lamivudine and all lamivudine related impurities from the Sample solution
Calculate the percentage of each zidovudine related impurity and unidentified impurity in the portion of Tablets taken:
Result = (rU/rT) × (1/F) × 100
rU== peak response of each individual impurity from the Sample solution
rT== sum of the peak responses of zidovudine, all zidovudine related impurities, and unidentified impurities from the Sample solution
F== relative response factor (see Table 2)
Acceptance criteria:  See Table 2.
Table 2
Name Relative
Retention
Time
Relative
Response
Factor
Acceptance
Criteria,
NMT (%)
Lamivudine-(cytosine)a 0.11 1.0 *
Lamivudine-(uracil)b 0.14 1.0 *
Lamivudine-(carboxylic acid)c 0.17 1.0 0.3
Lamivudine-(S-sulfoxide)d 0.20 1.0 *
Lamivudine-(R-sulfoxide)e 0.22 1.0 *
Zidovudine related compound Cf 0.27 1.7 1.5
Lamivudine diastereomerg 0.50 1.0 0.2
Lamivudine 0.52
Zidovudine-(thymidine)h 0.60 1.0 *
Lamivudine-(uracil derivative)i 0.70 1.0 *
Lamivudine-(salicylic acid)j 0.80 1.0 *
Zidovudine 1.00
Zidovudine related compound Bk 1.10 1.0 *
Individual unidentified impurity 1.0 0.1
Total lamivudine related impurities (the limit includes all lamivudine related impurities) 0.6
Total zidovudine related impurities (the limit includes individual unidentified impurities) 2.0
a  4-Aminopyrimidin-2(1H)-one.
b  Pyrimidine-2,4(1H,3H)-dione.
c  (2R,5S)-5-(4-Amino-2-oxopyrimidin-1(2H)-yl)-1,3-oxathiolane-2-carboxylic acid (2R,5S)-5-(cytosine-1-yl)-1,3-oxathiolane-2-carboxylic acid.
d  1-[(2R,3S,5SS)-2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine S-oxide.
e  1-[(2R,3R,5S)-2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine S-oxide.
f  5-Methylpyrimidine-2,4(1H,3H)-dione.
g  1-[(2S,5S)-2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.
h  [1-(2-Deoxy--d-ribofuranosyl)]thymine.
i  (2RS,5SR)1-[(2R,5S)-2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]uracil.
j  2-Hydroxybenzoic acid.
k  3'-Chloro-3'-deoxythymidine.
*  The individual impurity limit is not included because these are processes/other impurities monitored individually in the drug substances.
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in well-closed containers, protected from light, and store between 2 and 30.
•  Labeling: When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.
•  USP Reference Standards 11
USP Lamivudine RS Click to View Structure
USP Lamivudine Resolution Mixture B RS Click to View Structure
USP Zidovudine RS Click to View Structure
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