Glyburide and Metformin Hydrochloride Tablets
DEFINITION
Glyburide and Metformin Hydrochloride Tablets contain NLT 90.0% and NMT 110.0% of the labeled amounts of glyburide (C23H28ClN3O5S) and metformin hydrochloride (C4H11N5·HCl).
IDENTIFICATION
•  A. Glyburide: The retention time of the glyburide peak of the Sample solution corresponds to that of the major peak of the Standard solution, as obtained in the Assay for Glyburide.
•  B. Metformin Hydrochloride: The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay for Metformin Hydrochloride.
ASSAY
•  Glyburide
Solution A:  28.8 g/L of monobasic ammonium phosphate
Mobile phase:  Acetonitrile and Solution A (40:60). Adjust with 1 N sodium hydroxide to a pH of 5.3.
Diluent:  Acetonitrile and water (50:50)
Standard stock solution:  0.25 mg/mL of USP Glyburide RS prepared as follows: Dissolve first in the acetonitrile, using 50% of the final volume, and then dilute with water to volume.
Standard solution:  0.025 mg/mL of USP Glyburide RS in Diluent, from the Standard stock solution
System suitability solution 1:  Prepare a solution containing 0.025 mg/mL of USP Glyburide Related Compound A RS in Diluent. Transfer 50 µL of this solution to a 50-mL volumetric flask, and dilute with Standard solution to volume.
System suitability solution 2:  5.0 mg/mL of USP Metformin Hydrochloride RS in System suitability solution 1
Sample solution:  Dissolve NLT 5 Tablets in Diluent by stirring with a magnetic stirring bar for a least 1 h. Dilute to obtain a solution containing 0.025 mg/mL of glyburide, based on the label claim. Centrifuge a portion of this solution at 3000 rpm for 10 min and use the clear supernatant. [Note—Retain a portion of this solution for the Assay for Metformin Hydrochloride. ]
Chromatographic system  
Mode:  LC
Detector:  UV 230 nm
Column:  4.6-mm × 15-cm; 5-µm packing L7
Column temperature:  40
Flow rate:  1.2 mL/min
Injection size:  100 µL
System suitability 
Sample:  System suitability solution 2
[Note—The relative retention time for the peak due to glyburide related compound A is about 0.30 with respect to glyburide. ]
Suitability requirements 
Capacity factor, k':  NLT 7 for the peak due to glyburide
Column efficiency:  NLT 3000 theoretical plates for the peak due to glyburide
Relative standard deviation:  NMT 1.5% for the peak due to glyburide
Relative standard deviation:  NMT 10% for the peak due to glyburide related compound A
Analysis 
Samples:  Standard solution and Sample solution
Record the chromatograms for about 1.25 times the retention time of the glyburide peak. Calculate the percentage of C23H28ClN3O5S in the Tablets taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of USP Glyburide RS in the Standard solution (mg/mL)
CU== nominal concentration of glyburide in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0% of glyburide label claim
•  Metformin Hydrochloride
Solution A:  Transfer 1.0 g each of sodium heptanesulfonate and sodium chloride to a 2000-mL volumetric flask. Add 1800 mL of water, and adjust with 0.06 M phosphoric acid to a pH of 3.85. Dilute with water to volume.
Mobile phase:  Acetonitrile and Solution A (10:90)
Diluent:  Acetonitrile and water (1:40)
Standard solution:  0.25 mg/mL of USP Metformin Hydrochloride RS in Diluent. [Note—Sonicate to achieve complete dissolution, if necessary. ]
System suitability stock solution:  25 µg/mL each of USP Metformin Related Compound B RS and USP Metformin Related Compound C RS in Diluent
System suitability solution:  Transfer 0.5 mL of the System suitability stock solution to a 50-mL volumetric flask, and dilute with Standard solution to volume.
Sample solution:  Dilute with water a portion of the retained Sample solution from the Assay for Glyburide to obtain 0.25 mg/mL of metformin hydrochloride based on the label claim.
Chromatographic system 
Mode:  LC
Detector:  UV 218 nm
Column:  3.9-mm × 30-cm; 10-µm packing L1
Column temperature:  30
Flow rate:  1 mL/min
Injection size:  5 µL
System suitability 
Sample:  System suitability solution
[Note—The relative retention times for metformin related compound B, metformin, and metformin related compound C are about 0.86, 1.0, and 2.1–2.3, respectively. (Metformin related compound C can have a variable retention time.) ]
Suitability requirements 
Resolution:  NLT 1.5 between metformin related compound B and metformin
Tailing factor:  0.8–2.0 for the metformin peak
Relative standard deviation:  NMT 1.5% for the metformin peak and NMT 10% for each of the peaks due to metformin related compound B and metformin related compound C.
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of C4H11N5·HCl in the Tablets taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of USP Metformin Hydrochloride RS in the Standard solution (mg/mL)
CU== nominal concentration of metformin hydrochloride in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0% of metformin label claim
PERFORMANCE TESTS
•  Dissolution 711
Glyburide 
Medium:  0.05 M boric acid and 0.05 M potassium chloride solution. Prepare by dissolving 3.09 g of boric acid and 3.73 g of potassium chloride in 250 mL of water, adjust with 1 N sodium hydroxide to a pH of 9.5, and dilute with water to 1 L; 500 mL.
Apparatus 2:  75 rpm
Time:  30 min
Standard solution:  Transfer 10 mg of USP Glyburide RS to a 100-mL volumetric flask. Dissolve in 20 mL of acetonitrile, and dilute with Medium to volume. Dilute further with Medium to obtain a solution having a glyburide concentration, in mg/mL, of L/500 where L is the label claim, in mg, of glyburide.
Sample solution:  Sample per Dissolution 711. Pass a portion of the solution under test through a 0.45-µm polypropylene filter or a 1-µm glass fiber filter. Dilute with Medium, if necessary.
Solution A:  28.7 mg/mL of monobasic ammonium phosphate in water
Mobile phase:  Solution A and acetonitrile (1:1). Adjust with 1 N sodium hydroxide to a pH of 5.3.
Chromatographic system 
Mode:  LC
Detector:  UV 230 nm
Column:  4.6-mm × 15-cm; 5-µm packing L7
Column temperature:  30
Flow rate:  1.5 mL/min
Injection size:  200 µL
System suitability 
Sample:  Standard solution
Suitability requirements 
Column efficiency:  NLT 5000
Tailing factor:  0.8–2.0
Relative standard deviation:  NMT 2%
Analysis 
Samples:  Standard solution and Sample solution
Determine the percentage of C23H28ClN3O5S dissolved:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of the Standard solution (mg/mL)
CU== nominal concentration of glyburide in the Sample solution (mg/mL)
Tolerances:  NLT 85% (Q) of the labeled amount of glyburide is dissolved.
Metformin hydrochloride 
Medium:  0.05 M phosphate buffer, pH 6.8. Prepare by dissolving 6.8 g of monobasic potassium phosphate in 1000 mL of water, and adjust with 0.2 N sodium hydroxide to a pH of 6.8 ± 0.1; 1000 mL.
Apparatus 2:  50 rpm
Time:  30 min
Standard solution:  Dissolve a quantity of USP Metformin Hydrochloride RS in Medium. Dilute further, if necessary, with Medium to obtain a solution having a metformin hydrochloride concentration, in mg/mL, of L/1000 where L is the label claim, in mg, of metformin hydrochloride.
Sample solution:  Sample per Dissolution 711. Pass a portion of the solution under test through a 0.45-µm polypropylene filter or a 1-µm glass fiber filter. Dilute with Medium, if necessary.
Spectrometric conditions 
Mode:  UV-Vis
Analytical wavelength:  232 nm
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of C4H11N5·HCl dissolved:
Result = (AU/AS) × (CS/CU) × 100
AU== absorbance of the Sample solution
AS== absorbance of the Standard solution
CS== concentration of USP Metformin Hydrochloride RS in the Standard solution (mg/mL)
CU== nominal concentration of metformin hydrochloride in the Sample solution (mg/mL)
Tolerances:  NLT 85% (Q) of the labeled amount of metformin hydrochloride is dissolved.
•  Uniformity of Dosage Units 905: Meet the requirements for Weight Variation for metformin hydrochloride and for Content Uniformity for glyburide
IMPURITIES
Organic Impurities 
•  Procedure 1: Glyburide
Solution A, Mobile phase, Diluent, Sample solution, Chromatographic system, and System suitability:  Proceed as directed in the Assay for Glyburide.
Standard solution:  Dilute 1.0 mL of the Standard solution from the Assay for Glyburide with Diluent to 100 mL.
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of each glyburide impurity in the Tablets:
Result = (rU/rS) × (CS/CU) × F × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of USP Glyburide RS in the Standard solution (mg/mL)
CU== nominal concentration of glyburide in the Sample solution (mg/mL)
F== relative response factor, use 0.8 for glyburide related compound A, and use 1.0 for all other impurities
Acceptance criteria 
[Note—Disregard any peak less than 0.05%, and disregard any peak observed in the blank. ]
Glyburide related compound A:  NMT 1.0%
Any other individual impurities:  NMT 0.2%
Total impurities:  NMT 0.50%, excluding glyburide related compound A
•  Procedure 2: Metformin Hydrochloride
Solution A, Mobile phase, Sample solution, Chromatographic system, and System suitability:  Proceed as directed in the Assay for Metformin Hydrochloride.
Analysis 
Sample:  Sample solution
Calculate the percentage of each impurity in the portion of Tablets taken:
Result = (rU/rT) × 100
rU== peak response for each impurity from the Sample solution
rT== sum of the responses of all peaks from the Sample solution
Acceptance criteria 
[Note—Disregard any peak less than 0.05%, and disregard any peak observed in the blank. ]
Individual impurities:  NMT 0.1%
Total impurities:  NMT 0.5 %
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight, light-resistant containers, and store at controlled room temperature.
•  USP Reference Standards 11
USP Glyburide RS Click to View Structure
USP Glyburide Related Compound A RS
(4-[2-(5-Chloro-2-methoxybenzamido)ethyl]benzenesulfonamide.
USP Metformin Hydrochloride RS Click to View Structure
USP Metformin Related Compound B RS
1-Methylbiguanide.
    C3H9N5         115.14
USP Metformin Related Compound C RS
Dimethylmelamine, or N,N-dimethyl-[1,3,5]triazine-2,4,6-triamine.
    C5H10N6        154.17
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
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Principal Scientific Liaison
1-301-816-8251
(SM32010) Monographs - Small Molecules 3
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
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USP35–NF30 Page 3350
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