Clobetasol Propionate Ointment
DEFINITION
Clobetasol Propionate Ointment is Clobetasol Propionate in a suitable ointment base. It contains NLT 90.0% and NMT 115.0% of the labeled amount of clobetasol propionate (C25H32ClFO5).
IDENTIFICATION
• A. Thin-Layer Chromatographic Identification Test 
201
201
Standard solution:
0.5 mg/mL of of USP Clobetasol Propionate RS in chloroform
Test solution:
Nominally 0.5 mg/mL of clobetasol propionate. Transfer a portion of Ointment equivalent to 1.0 mg of clobetasol propionate to a 25-mL, plastic-stoppered centrifuge tube. Add 10 mL of methanol, and cap. Heat in a 70
water bath for 4 min, remove the tube from the bath, and shake vigorously. Repeat the heating and shaking. Freeze the mixture in an ice bath for 5 min, and centrifuge at about 3500 rpm for 10 min. Transfer 5 mL of the supernatant to a suitable vial. Evaporate with the aid of a stream of nitrogen to dryness. Dissolve the residue in 1.0 mL of chloroform.
water bath for 4 min, remove the tube from the bath, and shake vigorously. Repeat the heating and shaking. Freeze the mixture in an ice bath for 5 min, and centrifuge at about 3500 rpm for 10 min. Transfer 5 mL of the supernatant to a suitable vial. Evaporate with the aid of a stream of nitrogen to dryness. Dissolve the residue in 1.0 mL of chloroform.
Developing solvent system:
Chloroform, acetone, and alcohol (100:10:5)
Acceptance criteria:
The RF value of the principal spot obtained from the Test solution corresponds to that from the Standard solution.
ASSAY
• Procedure
Buffer:
0.05 M monobasic sodium phosphate. Adjust with 85% phosphoric acid to a pH of 2.5.
Mobile phase:
Acetonitrile, methanol, and Buffer (95:20:85)
Internal standard solution:
0.2 mg/mL of beclomethasone dipropionate in methanol
System suitability solution:
0.001 mg/mL of USP Clobetasol Propionate Related Compound A RS and 0.1 mg/mL of USP Clobetasol Propionate RS in Mobile phase
Standard solution:
Dissolve a quantity of USP Clobetasol Propionate RS in methanol and Internal standard solution to obtain a final solution of 0.04 mg/mL of USP Clobetasol Propionate RS and 0.08 mg/mL of beclomethasone dipropionate
Sample solution:
Nominally 0.04 mg/mL of clobetasol propionate. Transfer a portion of Ointment equivalent to 1.0 mg of clobetasol propionate into a 125-mL separatory funnel. Add 30 mL of hexane, 10.0 mL of the Internal standard solution, and shake. Collect the lower layer in a 25-mL volumetric flask. Extract the hexane remaining in the separatory funnel with two 5-mL portions of Mobile phase, and combine all of the extracts in the 25-mL volumetric flask. Dilute with Mobile phase to volume, and pass a portion through a filter of 0.45-µm pore size.
Chromatographic system
Mode:
LC
Detector:
UV 240 nm
Column:
4.6-mm × 15-cm; packing L1
Flow rate:
1 mL/min
Injection size:
10 µL
System suitability
Sample:
System suitability solution
[Note—The relative retention times for clobetasol propionate and clobetasol propionate related compound A are 1.0 and 1.1, respectively. ]
Suitability requirements
Resolution:
NLT 1.5 between clobetasol propionate and clobetasol propionate related compound A
Column efficiency:
NLT 5000 theoretical plates for the clobetasol propionate peak
Tailing factor:
NMT 2.0 for the clobetasol propionate peak
Relative standard deviation:
NMT 2.0% for the clobetasol propionate peak
Analysis
Samples:
Standard solution and Sample solution
[Note—The relative retention times for clobetasol propionate and beclomethasone dipropionate are 1.0 and 1.6, respectively. ]
Calculate the percentage of clobetasol propionate (C25H32ClFO5) in the portion of Ointment taken:
Result = (RU/RS) × (CS/CU) × 100
| RU | = | = ratio of the clobetasol propionate peak area to the internal standard peak area from the Sample solution |
| RS | = | = ratio of the clobetasol propionate peak area to the internal standard peak area from the Standard solution |
| CS | = | = concentration of USP Clobetasol Propionate RS in the Standard solution (mg/mL) |
| CU | = | = nominal concentration of clobetasol propionate in the Sample solution (mg/mL) |
Acceptance criteria:
90.0%–115.0%
SPECIFIC TESTS
• Microbial Enumeration Tests 61 and Tests for Specified Microorganisms 62:
The total aerobic microbial count does not exceed 102 cfu/g. It meets the requirements of the tests for absence of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella species.
61 and Tests for Specified Microorganisms 62:
The total aerobic microbial count does not exceed 102 cfu/g. It meets the requirements of the tests for absence of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella species.
• Minimum Fill 755:
Meets the requirements
755:
Meets the requirements
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in collapsible tubes or in tight containers. Store at controlled room temperature. Do not refrigerate.
• USP Reference Standards 11
11
USP Clobetasol Propionate RS 
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USP Clobetasol Propionate Related Compound A RS
9
-Fluoro-11
-hydroxy-16-methyl 3-oxo-androsta-1,4-diene-17(R)-spiro-2¢-[4¢-chloro-5¢-ethylfuran-3¢(2¢H)-one].
C25H30ClFO4 448.96
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9
-Fluoro-11-hydroxy-16-methyl 3-oxo-androsta-1,4-diene-17(R)-spiro-2¢-[4¢-chloro-5¢-ethylfuran-3¢(2¢H)-one].
C25H30ClFO4 448.96
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Domenick Vicchio, Ph.D.
Senior Scientific Liaison 1-301-998-6828 |
(SM42010) Monographs - Small Molecules 4 |
| 61 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
| 62 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2715