Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Penicillin antibacterial.
DEFINITION
Cloxacillin Sodium Intramammary Infusion (Lactating Cow) is a sterile suspension of Cloxacillin Sodium in a suitable non- aqueous vehicle containing suitable suspending and dispersing agents.
The intramammary infusion complies with the requirements stated under Intramammary Infusions and with the following requirements.
Content of cloxacillin, C19H18ClN3O5S
90.0 to 110.0% of the stated amount.
IDENTIFICATION
Extract a quantity containing the equivalent of 75 mg of cloxacillin with three 15-mL quantities of petroleum spirit (boiling range, 120° to 160°). Discard the extracts, wash the residue with ether and dry in a current of air. The residue obtained complies with the following tests.
A. The infrared absorption spectrum, Appendix II A, is concordant with the reference spectrum of cloxacillin sodium (RSV 13).
B. Yields the reactions characteristic of sodium salts, Appendix VI.
Water
Not more than 1.0% w/w, Appendix IX C. Use 3 g and a mixture of 70 volumes of chloroform and 30 volumes of anhydrous methanol as the solvent.
ASSAY
Express, as far as possible, weigh and mix the contents of 10 containers. Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
(1) Extract a quantity of the mixed contents of the 10 containers containing the equivalent of 50 mg of cloxacillin with 15 mL of petroleum spirit (boiling range, 120° to 160°), centrifuge and discard the supernatant liquid. Repeat the extraction with a further two 15-mL quantities of petroleum spirit (boiling range, 120° to 160°). Shake the residue with 20 mL of ether, centrifuge and dry in a current of air until the solvents have evaporated. Dissolve the final residue in sufficient of the mobile phase to produce 50 mL and dilute 5 volumes of the resulting solution to 50 volumes with the mobile phase.
(2) 0.011% w/v of cloxacillin sodium BPCRS in the mobile phase.
(3) 0.01% w/v of each of cloxacillin sodium BPCRS and flucloxacillin sodium BPCRS in the mobile phase.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (5 µm) (Hypersil 5 ODS is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 225 nm.
(f) Inject 20 µL of each solution.
MOBILE PHASE
25 volumes of acetonitrile and 75 volumes of a 0.27% w/v solution of potassium dihydrogen orthophosphate adjusted to pH 5.0 with 2M sodium hydroxide.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution factor between the first peak (cloxacillin) and the second peak (flucloxacillin) is at least 2.5.
DETERMINATION OF CONTENT
Calculate the content of C19H18ClN3O5S in a container of average content weight using the declared content of C19H17ClN3NaO5S in cloxacillin sodium BPCRS. Each mg of C19H17ClN3NaO5S is equivalent to 0.9520 mg of C19H18ClN3O5S.
LABELLING
The quantity of active ingredient is stated in terms of the equivalent amount of cloxacillin.
