Cephalexin Tablets for Oral Suspension
DEFINITION
Cephalexin Tablets for Oral Suspension contain NLT 90.0% and NMT 110.0% of the labeled amount of cephalexin (C16H17N3O4S).
IDENTIFICATION
•  The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
ASSAY
•  Procedure
Mobile phase:  0.985 g/L of sodium 1-pentanesulfonate in a mixture of acetonitrile, methanol, triethylamine, and water (20:10:3:170), adjusted with phosphoric acid to a pH of 3.0 ± 0.1
Standard stock solution:  1 mg/mL of USP Cephalexin RS in water
Standard solution:  0.4 mg/mL of cephalexin in Mobile phase from Standard stock solution
Sample stock solution:  Nominally equivalent to 1 mg/mL of cephalexin from combined contents of NLT 20 powdered Tablets for Oral Suspension in water. Pass a portion of the solution through a filter having a 1-µm or finer pore size.
Sample solution:  0.4 mg/mL of cephalexin in Mobile phase from Sample stock solution
Chromatographic system
Mode:  LC
Detector:  UV 254 nm
Column:  4.6-mm × 25-cm; packing L1 of low acidity
Flow rate:  1.5 mL/min
Injection size:  20 µL
System suitability
Sample:  Standard solution
Suitability requirements
Relative standard deviation:  NMT 2.0%
Analysis
Samples:  Standard solution and Sample solution
Calculate the percentage of cephalexin (C16H17N3O4S) in each Tablet for Oral Suspension:
Result = (rU/rS) × (CS/CU) × P × F × 100
 rU = = peak response from the Sample solution rS = = peak response from the Standard solution CS = = concentration of USP Cephalexin RS in the Standard stock solution (mg/mL) CU = = nominal concentration of cephalexin in the Sample stock solution (mg/mL) P = = potency of cephalexin in USP Cephalexin RS (µg/mg) F = = conversion factor, 0.001 mg/µg
Acceptance criteria:  90.0%–110.0%
PERFORMANCE TESTS
Tablets for Oral Suspension disintegrate in 3 min, using water at 20 ± 5.
Medium:  Water; 900 mL
Apparatus 1:  Use 40-mesh cloth and 100 rpm.
Time:  30 min
Standard solution:  20 µg/mL of USP Cephalexin RS in Medium
Sample solution:  Pass a portion of the solution under test through a suitable filter. Dilute with Medium, if necessary, to a concentration of about 20 µg/mL.
Spectrometric conditions
Mode:  UV
Analytical wavelength:  262 nm
Analysis
Samples:  Standard solution and Sample solution
Tolerances:  NLT 80% (Q) of the labeled amount of cephalexin (C16H17N3O4S) is dissolved.
•  Dispersion Fineness: Place 2 Tablets for Oral Suspension in 100 mL of water, and stir until completely dispersed. A smooth dispersion is obtained that passes through a No. 25 sieve.
Meets the requirements
•  Packaging and Storage: Preserve in tight containers at controlled room temperature.
USP Cephalexin RS
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Topic/Question Contact Expert Committee
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(SM12010) Monographs - Small Molecules 1
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USP35–NF30 Page 2588
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