Bupivacaine Injection

Local anaesthetic.

Bupivacaine Injection is a sterile solution of Bupivacaine Hydrochloride in Water for Injections.

The injection complies with the requirements stated under Parenteral Preparations and with the following requirements.

92.5 to 107.5% of the stated amount.

A colourless or almost colourless solution.

A. To a volume of the injection containing the equivalent of 25 mg of anhydrous bupivacaine hydrochloride add 2 mL of 13.5m ammonia, shake and filter. Wash the precipitate with water and dry at 60° at a pressure of 2 kPa for 16 hours. The infrared absorption spectrum of the dried residue, Appendix II A, is concordant with the reference spectrum of bupivacaine (RS 034).

B. To a volume of the injection containing the equivalent of 50 mg of anhydrous bupivacaine hydrochloride add 2 mL of a 10% w/v solution of disodium hydrogen orthophosphate and sufficient iodinated potassium iodide solution to produce a distinct brown colour. Remove the excess iodine by adding 0.1m sodium thiosulfate. No pink colour is produced.

pH, 4.0 to 6.5, Appendix V L.

To a volume of the injection containing the equivalent of 25 mg of anhydrous bupivacaine hydrochloride add sufficient water, if necessary, to produce 10 mL, add 2m sodium hydroxide until the solution is just alkaline and extract with three 5 mL quantities of dichloromethane. Dry the combined dichloromethane extracts over anhydrous sodium sulfate, filter, wash with a further 5 mL of dishloromethane and evaporate the filtrate to dryness using a rotary evaporator. Dissolve the residue in 2 mL of methanol, add 1 mL of a 1% w/v solution of 4-dimethylaminobenzaldehyde in methanol and 2 mL of glacial acetic acid and allow to stand at room temperature for 10 minutes. The yellow colour produced is not more intense than the colour produced by repeating the operation using 10 mL of a solution in water containing 1 µg of 2,6-dimethylaniline per mL in place of the injection (400 ppm).

Carry out the method for thin-layer chromatography, Appendix III A, using silica gel G as the coating substance and a mixture of 0.1 volume of 13.5m ammonia and 100 volumes of methanol as the mobile phase but allowing the solvent front to ascend 10 cm above the line of application. Apply separately to the plate 10 µL of each of the following solutions. For solution (1) evaporate a volume of the injection containing the equivalent of 0.1 g of anhydrous bupivacaine hydrochloride using a rotary evaporator, add sufficient methanol to the residue to produce 2 mL, mix, centrifuge and use the supernatant liquid. For solution (2) dilute 1 volume of solution (1) to 100 volumes with methanol. After removal of the plate, allow it to dry in air and spray with dilute potassium iodobismuthate solution. Any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%).

Carry out the method for liquid chromatography, Appendix III D, using the following solutions. For solution (1) dilute a quantity of the injection with sufficient of the mobile phase to produce a solution containing 0.0025% w/v of anhydrous bupivacaine hydrochloride. Solution (2) contains 0.0025% w/v of bupivacaine hydrochloride BPCRS in the mobile phase. For solution (3) prepare a 0.1% w/v solution of 2,6-dimethylaniline in acetonitrile, dilute 10 volumes to 20 volumes with the mobile phase and then dilute 1 volume of the resulting solution to 100 volumes with solution (2).

The chromatographic procedure may be carried out using (a) a stainless steel column (30 cm × 3.9 mm) packed with end-capped octadecylsilyl silica gel for chromatography (10 µm) (µBondapak C18 is suitable), (b) a mixture of 40 volumes of 0.02m phosphate buffer pH 8.0 and 60 volumes of acetonitrile as the mobile phase with a flow rate of 1 mL per minute and (c) a detection wavelength of 240 nm. Inject 20 µL of each solution.

The test is not valid unless in the chromatogram obtained with solution (3) the resolution factor between the two principal peaks is at least 8.

Calculate the content of C₁₈H₂₈N₂O,HCl in the injection using the declared content of C₁₈H₂₈N₂O,HCl in bupivacaine hydrochloride BPCRS.

The strength is stated in terms of the equivalent amount of anhydrous bupivacaine hydrochloride in a suitable dose-volume.