Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Glucocorticoid.
DEFINITION
Betamethasone Eye Drops are a sterile solution of Betamethasone Sodium Phosphate in Purified Water.
The eye drops comply with the requirements stated under Eye Preparations and with the following requirements.
Content of betamethasone sodium phosphate, C22H28FNa2O8P
90.0 to 110.0% of the stated amount.
IDENTIFICATION
A. Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
(1) Use the eye drops, diluted if necessary with water, to contain 0.1% w/v of Betamethasone Sodium Phosphate.
(2) 0.1% w/v of betamethasone sodium phosphate BPCRS.
(3) A mixture of equal volumes of solutions (1) and (2).
(4) A mixture of equal volumes of solution (2) and a 0.1% w/v solution of prednisolone sodium phosphate BPCRS.
CHROMATOGRAPHIC CONDITIONS
(a) Use as the coating silica gel GF254.
(b) Use the mobile phase as described below.
(c) Apply 10 μL of each solution.
(d) Develop the plate to 15 cm.
(e) After removal of the plate, 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, prepared immediately before use.
SYSTEM SUITABILITY
The test is not valid unless the chromatogram obtained with solution (4) shows two principal spots with almost identical Rf values.
CONFIRMATION
The chromatograms obtained with solutions (1), (2) and (3) show single principal spots with similar Rf values.
B. In the Assay, the chromatogram obtained with solution (2) shows a peak with the same retention time as the peak due to betamethasone sodium phosphate in the chromatogram obtained with solution (1).
C. To a volume containing 0.2 mg of Betamethasone Sodium Phosphate, add slowly 1 mL of sulfuric acid and allow to stand for 2 minutes. A brownish yellow colour but no red colour or yellowish green fluorescence is produced.
TESTS
Acidity or alkalinity
pH, 7.0 to 8.5, Appendix V L.
Related substances
Carry out the method for liquid chromatography, Appendix III D, protected from light and using the following solutions in the mobile phase.
(1) Dilute the eye drops if necessary to give a solution containing 0.10% w/v of Betamethasone Sodium Phosphate.
(2) Dilute 1 volume of solution (1) to 50 volumes with water.
(3) 0.0060% w/v each of betamethasone sodium phosphate BPCRS and betamethasone.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (20 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.
(g) 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.
(1) Mix a quantity of the eye drops containing 5 mg of Betamethasone Sodium Phosphate with 10 mL of methanol and dilute to 25 mL with water.
(2) A mixture of 5 mL of a 0.1% w/v solution of betamethasone sodium phosphate BPCRS in water (solution A) and 10 mL of a 0.06% w/v solution of hydrocortisone (internal standard) in methanol and sufficient water to produce 25 mL.
(3) Prepare in the same manner as solution (1) but using 10 mL of the internal standard solution in place of the methanol.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (20 cm × 5 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 C22H28FNa2O8P in solution A by measuring the absorbance, Appendix II B, of an aliquot diluted with water to contain 0.002% w/v of Betamethasone Sodium Phosphate at the maximum at 241 nm and taking 297 as the value of A(1%, 1 cm) at the maximum at 241 nm. Calculate the content of C22H28FNa2O8P in the eye drops using peak areas.
STORAGE
Betamethasone Eye Drops should be protected from light.
