Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Antibacterial.
Preparation
Sodium Fusidate Ointment Ph Eur
DEFINITION
Sodium ent-(17Z)-16α-(acetyloxy)-3β,11β-dihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dien-21-oate. Antimicrobial substance produced by fermentation of certain strains of Fusidium coccineum or by any other means.
Content
97.5 per cent to 101.0 per cent (anhydrous substance).
CHARACTERS
Appearance
White or almost white, crystalline powder, slightly hygroscopic.
Solubility
Freely soluble in water and in ethanol (96 per cent).
IDENTIFICATION
A. Infrared absorption spectrophotometry (2.2.24).
Comparison sodium fusidate CRS.
B. Ignite 1 g. The residue gives reaction (a) of sodium (2.3.1).
TESTS
Appearance of solution
The solution is not more intensely coloured than reference solution B6 (2.2.2, Method II). Dissolve 1.5 g in 10 mL of water R.
pH (2.2.3)
7.5 to 9.0.
Dissolve 0.125 g in 10 mL of carbon dioxide-free water R.
Related substances
Liquid chromatography (2.2.29). Prepare the solutions immediately before use.
Solvent mixture methanol R, 5 g/L solution of phosphoric acid R, acetonitrile R (10:40:50 V/V/V).
Test solution Dissolve 25 mg of the substance to be examined in the solvent mixture and dilute to 10.0 mL with the solvent mixture.
Reference solution (a) Dissolve 2 mg of fusidic acid for peak identification CRS (containing impurities A, B, C, D, F, G, H and N) in the solvent mixture and dilute to 1.0 mL with the solvent mixture.
Reference solution (b) Dilute 1.0 mL of the test solution to 100.0 mL with the solvent mixture.
Reference solution (c) Dilute 1.0 mL of reference solution (b) to 10.0 mL with the solvent mixture.
Reference solution (d) Dissolve the contents of a vial of fusidic acid impurity mixture CRS (containing impurities I, K, L and M) in 1.0 mL of the solvent mixture.
Column:
— size: l = 0.15 m, Ø = 4.6 mm;
— stationary phase: end-capped octadecylsilyl silica gel for chromatography R (3.5 µm);
— temperature: 30 °C.
Mobile phase:
— mobile phase A: methanol R, acetonitrile R, 5 g/L solution of phosphoric acid R (20:40:40 V/V/V);
— mobile phase B: 5 g/L solution of phosphoric acid R, methanol R, acetonitrile R (10:20:70 V/V/V);
| Time (min) | Mobile phase A (per cent V/V) | Mobile phase B (per cent V/V) |
| 0 – 3 | 100 | 0 |
| 3 – 28 | 100 → 0 | 0 → 100 |
| 28 – 33 | 0 | 100 |
Flow rate 1.0 mL/min.
Detection Spectrophotometer at 235 nm.
Injection 20 µL.
Identification of impurities Use the chromatogram supplied with fusidic acid for peak identification CRS and the chromatogram obtained with reference solution (a) to identify the peaks due to impurities A, B, C, D, F, G, H and N; use the chromatogram supplied with fusidic acid impurity mixture CRS and the chromatogram obtained with reference solution (d) to identify the peaks due to impurities I, K, L and M.
Relative retention With reference to fusidic acid (retention time = about 18 min): impurity A = about 0.4; impurity B = about 0.5; impurity C = about 0.6; impurity D = about 0.63; impurity N = about 0.65; impurity F = about 0.7; impurity G = about 0.82; impurity H = about 0.85; impurity I = about 0.96; impurity K = about 1.18; impurity L = about 1.23; impurity M = about 1.4.
System suitability Reference solution (a):
— resolution: minimum 1.5 between the peaks due to impurities G and H.
Limits:
— correction factors: for the calculation of content, multiply the peak areas of the following impurities by the corresponding correction factor: impurity C = 0.7; impurity D = 0.7; impurity F = 0.3; impurity I = 0.6; impurity K = 0.6;
— impurity M: not more than the area of the principal peak in the chromatogram obtained with reference solution (b) (1.0 per cent);
— impurity G: not more than 0.7 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.7 per cent);
— impurity L: not more than 0.5 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.5 per cent);
— impurity B: not more than 4 times the area of the principal peak in the chromatogram obtained with reference solution (c) (0.4 per cent);
— impurity A: not more than 3 times the area of the principal peak in the chromatogram obtained with reference solution (c) (0.3 per cent);
— impurities C, D, F, I, K, N: for each impurity, not more than twice the area of the principal peak in the chromatogram obtained with reference solution (c) (0.2 per cent);
— unspecified impurities: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (c) (0.10 per cent);
— total: not more than twice the area of the principal peak in the chromatogram obtained with reference solution (b) (2.0 per cent);
— disregard limit: 0.5 times the area of the principal peak in the chromatogram obtained with reference solution (c) (0.05 per cent).
Water (2.5.12)
Maximum 2.0 per cent, determined on 0.500 g.
ASSAY
Dissolve 0.400 g in 30 mL of water R and add 40 mL of ethanol (96 per cent) R. Titrate with 0.1 M hydrochloric acid, determining the end-point potentiometrically (2.2.20).
1 mL of 0.1 M hydrochloric acid is equivalent to 53.87 mg of C31H47NaO6.
STORAGE
In an airtight container, protected from light, at a temperature of 2 °C to 8 °C.
IMPURITIES
Specified impurities A, B, C, D, F, G, I, K, L, M, N.
Other detectable impurities (the following substances would, if present at a sufficient level, be detected by one or other of the tests in the monograph. They are limited by the general acceptance criterion for other/unspecified impurities and/or by the general monograph Substances for pharmaceutical use (2034). It is therefore not necessary to identify these impurities for demonstration of compliance. See also 5.10. Control of impurities in substances for pharmaceutical use) E, H, J, O.
A. ent-(24SR,17Z)-16α-(acetyloxy)-3β,11β,24,25-tetrahydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholest-17(20)-en-21-oic acid (24,25-dihydro-24,25-dihydroxyfusidic acid),
B. ent-(17Z)-3β,11β-dihydroxy-17-[(6SR)-6-hydroxy-7,7-dimethyl-2-oxooxepan-3-ylidene]-4β,8,14-trimethyl-18-nor- 5β,10α-androstan-16α-yl acetate (24,25-dihydro-24,25-dihydroxyfusidic acid 21,25-lactone),
C. ent-(17Z)-3β,11β-dihydroxy-17-[(6S)-6-(1-hydroxy-1-methylethyl)-2-oxodihydro-2H-pyran-3(4H)-ylidene]-4β,8,14- trimethyl-18-nor-5β,10α-androstan-16α-yl acetate ((24R)-24,25-dihydro-24,25-dihydroxyfusidic acid 21,24-lactone),
D. ent-(17Z)-3β,11β-dihydroxy-17-[(6R)-6-(1-hydroxy-1-methylethyl)-2-oxodihydro-2H-pyran-3(4H)-ylidene]-4β,8,14- trimethyl-18-nor-5β,10α-androstan-16α-yl acetate ((24S)-24,25-dihydro-24,25-dihydroxyfusidic acid 21,24-lactone),
E. ent-(17Z,24EZ)-16α-(acetyloxy)-3β,11β,26-trihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (26-hydroxyfusidic acid),
F. ent-(17Z,24EZ)-16α-(acetyloxy)-3β,11β-dihydroxy-4β,8,14-trimethyl-26-oxo-18-nor-5β,10α-cholesta-17(20),24-dien-21- oic acid (26-oxofusidic acid),
G. ent-(17Z)-16α-(acetyloxy)-11β-hydroxy-4β,8,14-trimethyl-3-oxo-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (3- didehydrofusidic acid),
H. ent-(17Z)-16α-(acetyloxy)-3β-hydroxy-4β,8,14-trimethyl-11-oxo-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (11-didehydrofusidic acid),
I. ent-(17Z)-3β,11β,16β-trihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (16-epi- deacetylfusidic acid),
J. ent-(17Z)-3β,11β-dihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dieno-21(16β)-lactone (16-epi- deacetylfusidic acid 21,16-lactone),
K. ent-(17Z)-3β,11β-dihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dieno-21(16α)-lactone (deacetylfusidic acid 21,16-lactone),
L. ent-(17Z)-16α-(acetyloxy)-3β-hydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-9(11),17(20),24-trien-21-oic acid (9,11-anhydrofusidic acid),
M. ent-(17Z)-16α-(acetyloxy)-3β-hydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (11- deoxyfusidic acid),
N. unknown structure,
O. ent-(17Z)-3β,11β,16α-trihydroxy-4β,8,14-trimethyl-18-nor-5β,10α-cholesta-17(20),24-dien-21-oic acid (deacetylfusidic acid).
