U.S. PHARMACOPEIA

Search USP29  
Cephalexin for Oral Suspension
» 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 not less than 90.0 percent and not more than 120.0 percent of the labeled amount of C16H17N3O4S per mL when constituted as directed in the labeling.
Packaging and storage— Preserve in tight containers.
Identification— Constitute 1 container of Cephalexin for Oral Suspension as directed in the labeling. Mix a portion of the resulting suspension with water to obtain a concentration of about 3 mg of cephalexin per mL, and filter (test solution). Proceed as directed in the Identification test under Cephalexin Capsules, beginning with “Place a suitable thin-layer chromatographic plate”: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Uniformity of dosage units 905—
FOR SOLID PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.
Deliverable volume 698: meets the requirements.
pH 791: between 3.0 and 6.0, in the suspension constituted as directed in the labeling.
Water, Method I 921: not more than 2.0%.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
Mobile phase— Prepare as directed in the Assay under Cephalexin.
Standard preparation— Dissolve an accurately weighed quantity of USP Cephalexin RS quantitatively in water to obtain a stock solution having a known concentration of about 1 mg per mL. Transfer 10.0 mL of this stock solution to a 50-mL, glass-stoppered flask, add 15.0 mL of Mobile phase, and mix.
Resolution solution— Transfer 300 mg of 1-hydroxybenzotriazole to a 1000-mL volumetric flask, dissolve in 10 mL of methanol, dilute with Mobile phase to volume, and mix. To 15.0 mL of this solution add 10.0 mL of the stock solution used to prepare the Standard preparation.
Assay preparation— Constitute Cephalexin for Oral Suspension as directed in the labeling. Transfer an accurately measured volume of the suspension so obtained, freshly mixed and free from air bubbles, equivalent to about 250 mg of cephalexin, to a 250-mL volumetric flask, dilute with water to volume, and mix. Sonicate, if necessary, to assure complete dissolution of the cephalexin. Filter, if necessary, to obtain a clear solution. Transfer 10.0 mL of this solution to a 50-mL glass-stoppered flask, add 15.0 mL of Mobile phase, mix, and filter.
Chromatographic system (see Chromatography 621)—Proceed as directed for Chromatographic system in the Assay under Cephalexin, except to chromatograph the Resolution solution to confirm that the resolution, R, between the 1-hydroxybenzotriazole peak and the cephalexin peak is not less than 5. The relative retention times are about 0.35 for 1-hydroxybenzotriazole and 1.0 for cephalexin.
Procedure— Proceed as directed for Procedure in the Assay under Cephalexin. Calculate the quantity, in mg, of C16H17N3O4S in each mL of the constituted Suspension taken by the formula:
0.25(CP / V)(rU / rS),
in which V is the volume, in mL, of the constituted Suspension taken, rU and rS are the cephalexin peak responses obtained from the Assay preparation and the Standard preparation, respectively, and the other terms are as defined therein.
Auxiliary Information— Staff Liaison : Brian D. Gilbert, Ph.D., Scientist
Expert Committee : (MDANT05) Monograph Development-Antibiotics
USP29–NF24 Page 449
Phone Number : 1-301-816-8223