Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Glucocorticoid.
DEFINITION
Betamethasone Injection is a sterile solution of Betamethasone Sodium Phosphate in Water for Injections.
The injection complies with the requirements stated under Parenteral Preparations and with the following requirements.
Content of betamethasone, C22H29FO5
92.5 to 107.5% of the stated amount.
IDENTIFICATION
A. To a volume of the injection containing the equivalent of 4 mg of betamethasone add 1 mL of water and sufficient absolute ethanol to produce 40 mL. Place 2 mL of the solution in a stoppered tube, add 10 mL of phenylhydrazine-sulfuric acid solution, mix, warm in a water bath at 60° for 20 minutes and cool immediately. The absorbance of the resulting solution at the maximum at 450 nm is not more than 0.1, Appendix II B.
B. Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
(1) Dilute the injection, if necessary, with sufficient water to produce a solution containing the equivalent of 2 mg of betamethasone per mL.
(2) 0.25% w/v solution of betamethasone sodium phosphate BPCRS in water.
(3) A mixture of equal volumes of solutions (1) and (2).
(4) A mixture of equal volumes of solution (1) and a 0.25% w/v solution of prednisolone sodium phosphate BPCRS in water.
CHROMATOGRAPHIC CONDITIONS
(a) Use as the coating silica gel GF254.
(b) Use the mobile phase as described below and prepare immediately before use.
(c) Apply 5 µL of each solution.
(d) Develop the plate to 15 cm.
(e) After removal of the plate, allow it to dry in air, heat at 110° for 10 minutes and examine under ultraviolet light (254 nm).
MOBILE PHASE
20 volumes of acetic anhydride, 20 volumes of water and 60 volumes of butan-1-ol.
CONFIRMATION
The chromatograms obtained with solutions (1), (2) and (3) show single spots with similar Rf values;
the chromatogram obtained with solution (4) shows two principal spots with almost identical Rf values.
Secondary spots due to excipients may also be observed in the chromatograms obtained with solutions (1), (3) and (4).
C. Evaporate a volume containing the equivalent of 2 mg of betamethasone to dryness on a water bath, dissolve the residue in 2 mL of sulfuric acid and allow to stand for 2 minutes. No red colour is produced.
TESTS
Alkalinity
pH, 8.0 to 9.0, Appendix V L.
Colour
The injection, diluted if necessary with water to contain the equivalent of 2 mg of betamethasone per mL, is not more intensely coloured than reference solution BY4, Appendix IV B, Method I.
Related substances
Carry out the method for liquid chromatography, Appendix III D, protected from light, using the following solutions.
(1) Dilute the injection with mobile phase, if necessary, to give a solution containing the equivalent of 0.10% w/v of betamethasone.
(2) Dilute 1 volume of solution (1) to 50 volumes with mobile phase.
(3) 0.0060% w/v each of betamethasone sodium phosphate BPCRS and betamethasone in mobile phase.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (10 µm) (Spherisorb ODS 1 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 2 mL per minute.
(d) Use a column temperature of 60°.
(e) Use a detection wavelength of 241 nm.
(f) Inject 20 µL of each solution. For solutions (1) and (2) record the chromatogram for three times the retention time of the principal peak.
MOBILE PHASE
40 volumes of methanol and 60 volumes of citro-phosphate buffer pH 5.0.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution factor between the peaks due to betamethasone sodium phosphate and betamethasone is at least 3.5.
LIMITS
In the chromatogram obtained with solution (1):
the area of any peak corresponding to betamethasone is not greater than 1.3 times the area of the principal peak in the chromatogram obtained with solution (2)(2.6%);
the area of any other secondary peak is not greater than 1.5 times the area of the principal peak in the chromatogram obtained with solution (2)(3%);
the sum of the areas of all the secondary peaks is not greater than 2.5 times the area of the principal peak in the chromatogram obtained with solution (2)(5%).
Disregard any peak the area of which is less than 0.05 times the area of the principal peak in the chromatogram obtained with solution (2)(0.1%).
ASSAY
Carry out the method for liquid chromatography, Appendix III D, using the following solutions protected from light.
(1) Dilute a volume of the injection containing the equivalent of 8 mg of betamethasone to 50 mL with methanol (50%).
(2) Dilute 5 mL of a 0.045% w/v solution of betamethasone sodium phosphate BPCRS in water (solution A) to 10 mL with methanol.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (10 µm) (Spherisorb ODS 1 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 2 mL per minute.
(d) Use a column temperature of 60°.
(e) Use a detection wavelength of 241 nm.
(f) Inject 20 µL of each solution.
MOBILE PHASE
45 volumes of methanol and 55 volumes of citro-phosphate buffer pH 5.0.
DETERMINATION OF CONTENT
Calculate the content of C22H29FO5 in the injection, determining the exact strength of C22H29FO5 in solution (2) as follows. Dilute 3 mL of solution A to 50 mL with water and measure the absorbance, Appendix II B, of the resulting solution at the maximum at 241 nm, taking 391 as the value of A(1%, 1 cm) for betamethasone.
STORAGE
Betamethasone Injection should be stored at a temperature not exceeding 30° and protected from light.
LABELLING
The quantity of active ingredient is stated in terms of the equivalent amount of betamethasone in a suitable dose-volume.
