Cefixime for Oral Suspension
Cefixime for Oral Suspension is a dry mixture of Cefixime and one or more suitable diluents, flavors, preservatives, and suspending agents. It contains the equivalent of NLT 90.0% and NMT 120.0% of the labeled amount of cefixime (C16H15N5O7S2)/mL when constituted as directed in the labeling.
•  The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
•  Procedure
Solution A:  0.4 M tetrabutylammonium hydroxide solution and water (1:39). Adjust with 1.5 M phosphoric acid to a pH of 6.5.
Solution B:  13.6 mg/mL of monobasic potassium phosphate
Solution C:  14.2 mg/mL of anhydrous dibasic sodium phosphate. Adjust a volume of this solution with a sufficient volume of Solution B to a pH of 7.0.
Mobile phase:  Acetonitrile and Solution A (1:3)
System suitability solution:  1 mg/mL of USP Cefixime RS. [Note—Heat this solution at 95 in an oil bath for 45 min, cool, and use promptly. ]
Standard solution:  0.2 mg/mL of USP Cefixime RS in Solution C. [Note—Use this solution promptly. ]
Sample solution:  Constitute Cefixime for Oral Suspension as directed in the labeling. Quantitatively dilute a suitable aliquot of the suspension, freshly mixed and free from air bubbles, with Solution C to obtain a solution having a nominal concentration of 0.2 mg of cefixime/mL.
Chromatographic system 
Mode:  LC
Detector:  UV 254 nm
Column:  4.6-mm × 12.5-cm; 4-µm packing L1
Temperature:  40
Flow rate:  Adjust flow rate so that the retention time of cefexime is about 10 min.
Injection size:  10 µL
System suitability 
Samples:  System suitability solution and Standard solution
[Note—The relative retention times for cefixime (E)-isomer and cefixime are about 0.9 and 1.0, respectively. ]
Suitability requirements 
Resolution:  NLT 2.0 between cefixime and cefixime (E)-isomer, System suitability solution
Column efficiency:  NLT 4000 theoretical plates, Standard solution. Use the following formula to calculate column efficiency:
Result = 5.545(t/Wh/2)2
Tailing factor:  NLT 0.9 and NMT 2.0 for the analyte peak, Standard solution. Use the following formula to calculate tailing factor:
Result = W0.1/2f
W0.1== peak width at 10% peak height
Relative standard deviation:  NMT 2.0%, Standard solution
Samples:  Standard solution and Sample solution
Calculate the percentage of C16H15N5O7S2 in the constituted suspension prepared from the Cefixime for Oral Suspension:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response of cefixime from the Sample solution
rS== peak response of cefixime from the Standard solution
CS== concentration of USP Cefixime RS in the Standard solution (mg/mL)
CU== nominal concentration of cefixime in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–120.0%
•  Uniformity of Dosage Units 905 FOR SOLIDS PACKAGED IN SINGLE-UNIT CONTAINERS: Meets the requirements
•  Deliverable Volume 698: Meets the requirements
•  pH 791: 2.5–4.5, in the suspension constituted as directed in the labeling
•  Packaging and Storage: Preserve in tight containers.
•  Labeling: Label it to indicate that the cefixime contained therein is in the trihydrate form.
•  USP Reference Standards 11
USP Cefixime RS Click to View Structure
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
(SM12010) Monographs - Small Molecules 1
Reference Standards RS Technical Services
USP35–NF30 Page 2548
Pharmacopeial Forum: Volume No. 34(6) Page 1441