Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Penicillin antibacterial.
DEFINITION
Cloxacillin Benzathine Intramammary Infusion (Dry Cow) is a sterile suspension of Cloxacillin Benzathine in a suitable non- aqueous vehicle containing suitable suspending 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 of the infusion 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 benzathine (RSV 12).
B. Shake 50 mg with 1 mL of 1M sodium hydroxide for 2 minutes, add 2 mL of ether, shake for 1 minute and allow to separate. Evaporate 1 mL of the ether layer to dryness, dissolve the residue in 2 mL of glacial acetic acid and add 1 mL of dilute potassium dichromate solution. A golden yellow precipitate is produced.
Water
Not more than 2.0% w/w, Appendix IX C. Use 3 g and a mixture of 70 volumes of chloroform and 30 volumes of anhydrous methanol as solvent.
ASSAY
Express, as far as possible, weigh and mix the contents of 10 containers. Extract a quantity of the mixed contents containing the equivalent of 80 mg of cloxacillin, with three 15 mL quantities of petroleum spirit (boiling range, 120° to 160°) previously saturated with cloxacillin benzathine. Discard the extract, wash the residue with ether previously saturated with cloxacillin benzathine, dry in a current of air, dissolve in 25 mL of methanol and dilute to 50 mL with water. Dilute 2 mL to 100 mL with buffered copper sulfate solution pH 2.0, transfer 10 mL to a stoppered test tube and heat in a water bath at 70° for 20 minutes. Rapidly cool to room temperature, dilute to 20 mL with absolute ethanol and measure the absorbance of the resulting solution at the maximum at 338 nm, Appendix II B, using in the reference cell 10 mL of the unheated buffered solution of the substance being examined, diluted to 20 mL with absolute ethanol.
Calculate the content of C19H18ClN3O5S in a container of average content from the absorbance obtained by carrying out the procedure simultaneously using 2 mL of a solution prepared by dissolving 105 mg of cloxacillin benzathine BPCRS in 50 mL of a mixture of equal volumes of methanol and water and from the declared content of C19H18ClN3O5S in cloxacillin benzathine BPCRS.
LABELLING
The quantity of active ingredient is stated in terms of the equivalent amount of cloxacillin.
