Cloxacillin Sodium
(klox'' a sil' in soe' dee um).
Click to View Image
C19H17ClN3NaO5S·H2O 475.88

4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, 6-[[[3-(2-chlorophenyl)-5-methyl-4-isoxazolyl]carbonyl]amino]-3,3-dimethyl-7-oxo-, monosodium salt, monohydrate, [2S-(2,5,6)]-.

Monosodium (2S,5R,6R)-6-[3-(o-chlorophenyl)-5-methyl-4-isoxazolecarboxamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate monohydrate [7081-44-9].

Anhydrous 457.87 [642-78-4].
» Cloxacillin Sodium contains the equivalent of not less than 825 µg of cloxacillin (C19H18ClN3O5S) per mg.
Packaging and storage— Preserve in tight containers, and store at a temperature not exceeding 25.
Labeling— Where it is intended for use in preparing sterile dosage forms, the label states that it is sterile or must be subjected to further processing during the preparation of sterile dosage forms.
USP Reference standards 11
USP Cloxacillin Sodium RS Click to View Structure
B: It responds to the tests for Sodium 191.
Crystallinity 695: meets the requirements.
Sterility 71 Where the label states that Cloxacillin Sodium is sterile, it meets the requirements when tested as directed for Direct Inoculation of the Culture Medium under Test for Sterility of the Product to be Examined, except to use Fluid Thioglycollate Medium containing polysorbate 80 solution (1 in 200) and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube, to use Soybean–Casein Digest Medium containing polysorbate 80 solution (1 in 200) and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube, and to shake the tubes once daily.
pH 791: between 4.5 and 7.5, in a solution containing 10 mg per mL.
Water, Method I 921: between 3.0% and 5.0%.
Dimethylaniline 223: meets the requirement.
Buffer— Prepare a 0.02 M solution of monobasic potassium phosphate in water, and adjust with 2 N sodium hydroxide to a pH of 6.8.
Mobile phase— Prepare a mixture of Buffer and acetonitrile (80:20). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation— Prepare a solution of USP Cloxacillin Sodium RS in Buffer having a known concentration of about 0.55 mg per mL.
Assay preparation— Transfer about 110 mg of Cloxacillin Sodium, accurately weighed, to a 200-mL volumetric flask, dilute with Buffer to volume, and mix. Stir with the aid of a magnetic stirrer for 5 minutes to dissolve.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 1.8; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of cloxacillin (C19H18ClN3O5S) in each mg of Cloxacillin Sodium taken by the formula:
200(CE / W)(rU / rS)
in which C is the concentration, in mg per mL, of USP Cloxacillin Sodium RS in the Standard preparation; E is the cloxacillin (C19H18ClN3O5S) equivalent, in µg per mg, of USP Cloxacillin Sodium RS; W is the weight, in mg, of Cloxacillin Sodium taken to prepare the Assay preparation; and rU and rS are the cloxacillin peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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
71 Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison
(GCM2010) General Chapters - Microbiology
USP35–NF30 Page 2747
Pharmacopeial Forum: Volume No. 28(4) Page 1091