Cephalexin for Oral Suspension
DEFINITION
Cephalexin for Oral Suspension is a dry mixture of Cephalexin and one or more suitable buffers, colors, diluents, and flavors. It contains the equivalent of NLT 90.0% and NMT 120.0% of the labeled amount of C16H17N3O4S per mL when constituted as directed in the labeling.
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:
Mix 10.0 mL of Standard stock solution with 15.0 mL of Mobile phase.
Sample stock solution:
Nominally equivalent to 1 mg/mL of cephalexin from Oral Suspension, constituted as directed in the labeling, freshly mixed and free from air bubbles. Sonicate, if necessary, to assure complete dissolution of the cephalexin. Filter, if necessary, to obtain a clear solution.
Sample solution:
Mix 10.0 mL of Sample stock solution and 15.0 mL of Mobile phase.
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 mL of the constituted Suspension taken:
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 from the Sample stock solution (mg/mL) |
| P | = | = potency of USP Cephalexin RS (µg/mg) |
| F | = | = conversion factor, 0.001 mg/µg |
Acceptance criteria:
90.0%–120.0%
PERFORMANCE TESTS
• Uniformity of Dosage Units 
905
For solid packaged in single-unit containers: meets the requirements
905
For solid packaged in single-unit containers: meets the requirements
• Deliverable Volume 698:
Meets the requirements
698:
Meets the requirements
SPECIFIC TESTS
• pH 791:
3.0–6.0, constituted as directed in the labeling
791:
3.0–6.0, constituted as directed in the labeling
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers.
• USP Reference Standards 11
11
USP Cephalexin RS 
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Ahalya Wise, M.S.
Senior Scientific Liaison 1-301-816-8161 |
(SM12010) Monographs - Small Molecules 1 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2587
Pharmacopeial Forum: Volume No. 36(1) Page 45