U.S. PHARMACOPEIA

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Cephapirin Benzathine Intramammary Infusion
» Cephapirin Benzathine Intramammary Infusion is a suspension of Cephapirin Benzathine in a suitable vegetable oil vehicle. It contains the equivalent of not less than 90.0 percent and not more than 120.0 percent of the labeled quantity of cephapirin (C17H17N3O6S2). It contains a suitable dispersing agent.
Packaging and storage— Preserve in well-closed unit-dose disposable syringes at controlled room temperature.
Labeling— Label Intramammary Infusion to indicate that it is for veterinary use only.
Identification, Infrared Absorption 197K— Prepare the test specimen as follows. Transfer the contents of 1 syringe of Intramammary Infusion to a 50-mL centrifuge tube, add 25 mL of toluene, mix for about 1 minute, and centrifuge. Remove and discard the toluene layer without disturbing the residue in the centrifuge tube. Wash the residue with two 25-mL portions of toluene. Dry the residue in vacuum at 60, and use the dried residue as the test specimen. Mix the dried residue with 9 parts of potassium bromide, and record the IR spectrum, using the diffuse reflectance technique: the IR absorption spectrum so obtained corresponds to that of a similar dispersion of USP Cephapirin Benzathine RS in potassium bromide.
Water, Method I 921: not more than 1.0%, 10 mL of Intramammary Infusion being tested.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
Solution A, Solution B, Mobile phase, Extraction solution, Dilution buffer, 10% Acetic acid solution, System suitability solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Cephapirin Benzathine.
Assay preparation— Express the entire contents of a syringe of the Intramammary Infusion into a centrifuge tube. For each mL of Intramammary Infusion, add 1.0 n-heptane and 1.5 mL of Extraction solution, cap, and vortex at high speed for 5 minutes. Centrifuge for 5 minutes at a sufficient speed to break the emulsion. Remove the aqueous layer, and pass through a 0.45-µm nylon filter, discarding the first 0.5 mL. Transfer 2.5 mL of the filtered aqueous phase into a 25-mL volumetric flask that contains a solution composed of 15.0 mL of Dilution buffer and 7.0 mL of acetonitrile. Add water to volume, and mix well to obtain a single phase.
Procedure— Separately inject equal volumes (about 2 µL) of the duplicate Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas of the major peaks. Calculate the quantity, in mg, of cephapirin (C17H17N3O6S2) in each syringe of Intramammary Infusion taken by the formula:
15PW(VU / VS)(rU / rS),
in which P is the assigned potency, in µg cephapirin per mg, of USP Cephapirin Sodium RS; W is the quantity of USP Cephapirin Sodium RS, in mg, used to prepare the Standard preparation; VS is the final volume, in mL, of the Standard preparation; VU is the entire volume of Intramammary Infusion, in mL, in one syringe; and rU and rS are the peak area and the average peak area of the cephapirin peaks obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Staff Liaison : Ian DeVeau, Ph.D., Associate Director
Expert Committee : (VET05) Veterinary Drugs 05
USP29–NF24 Page 453
Pharmacopeial Forum : Volume No. 30(2) Page 470
Phone Number : 1-301-816-8178