To develop a simultaneous related substances determination method. for Halobetasol propionate and Fusidic acid in cream formulation and

Transcription

1 CHAPTER 3 SIMULTANEOUS DETERMINATION OF HALOBETASOL PROPIONATE AND FUSIDIC ACID RELATED SUBSTANCES IN CREAM FORMULATION AND IDENTIFICATION OF IMPURITIES. 3.1 OBJECTIVE To develop a simultaneous related substances determination method for Halobetasol propionate and Fusidic acid in cream formulation and identification of Impurities. 3.2 INTRODUCTION Halobetasol propionate is one of the potent corticosteroid indicated in the relief of the inflammatory and pruritic manifestations of corticosteroid-responsive dermatitis [164,165]. Important treatment goals include providing moisture to the skin, preventing dryness and avoiding prurities, as a result the occurrence of inflammation should concomitantly decline. Fusidic acid is bacteriostatic antibiotic used in the treat of primary and secondary skin infections caused by sensitive strains of S.aureus, Strepto cocci species and C. Minutissimum [167] Halobetasol [ ] propionate is a synthetic corticosteroid. It is having anti-inflammatory, antipruritic and vasoconstrictor activities. Fusidic acid is the steroidal antibiotic is used to treat the gram positive infections. It acts by preventing translocation of peptidyl trna. Resistant mutants are easily 105

2 selected, even during therapy and therefore fusidic acid is usually administered in combination with another antibiotic. This helps reduce the risk of selecting resistant mutants. To survive, the fusidic acid resistant mutants become resistant to the antibiotic given in combination [173, 174]. 3.3 LITERATURE REVIEW: Giancarlo C. et al were reported degradation of halobetasol propionate in the presence of bases. The cyclization product was separated by isolation technique and fully characterized by MS, NMR and X-ray crystallography [175]. Hikal A.H. et al were reported a new HPLC method for the assay of sodium fusidate or fusidic acid in formulations and compared to a microbiological assay method. It was perfomred using test organism and agar diffusion technique with Staphylococcus aureus. With five test levels of the standard, potencies were interpolated from standard curve using a log transformation straight-line method with least-squares fitting (r = 0.99+). Both methods were applied to fusidic acid in tablets, a suspension, and an ointment. Excellent agrement was observed between results of the two methods [176]. Krzek J. et al were reported a thin-layer chromatography densitometric method for the identification and quantification of fusidic acid RF=0.53, methyl hydroxybenzoate RF=0.64, propyl hydroxybenzoate 106

3 RF=0.72, and butylated hydroxyanisol RF=0.77, which are the components of a dermatological ointment. Silica gel 60 F254 TLC plates were used as the stationary phase and mobile phase used was n- hexane-ethyl acetate-glacial acetic acid in the ratio of 6:3:1, v/v/v. Spots on chromatograms were detected by densitometric measurements at three different wavelengths of 240 nm for fusidic acid, 260 nm for methyl hydroxybenzoate, propyl hydroxybenzoate, and 290 nm for butylated hydroxyanisol, used for decreased interferences and increased selectivity of the peaks. Methdo found to be pricise, accuracte, and shown high sensitivity [177]. Shaikh S. et al were reported a simple, specific, and precise HPLC method for the simultaneous determination of chlorocresol, mometasone furoate, and fusidic acid in a cream. The mobile phase used was 1.5% w/v aqueous ammonium acetate buffer and acetonitrile, 55:45 v/v and adjusted ph 3.8, operated at the flow rate of 1.0mL/min. The column used was C8, 150 x 3.9 mm, 5 microm. The detection was done at 240 nm. The method resolves chlorocresol, mometasone furoate, and fusidic acid in less than 8 min with good resolution [178]. Kok-Khiang P. et al were reported a simple and selective HPLC with UV detection for simultaneous determination of fusidic acid and betamethasone dipropionate in a cream formulation. Chromatographic 107

4 separation was carried out by using C18 column and mobile phase consisting of acetonitrile and 0.01 M disodium hydrogen orthophosphate in the ratio 70:30, % v/v and adjusted to ph 6 with glacial acetic acid. Analysis was done at a flow rate of 1.0 ml/min; detection was carried at 235 nm [179]. 3.4 THEORETICAL ANALYSIS Sample information: Halobetasol propionate [180] is a molecule having chemical name as 21-chloro-6 alpha, 9-difluoro-11ß, 17-dihydroxy-16 ß-methylpregna-1, 4-diene-3-20-dione, 17-propionate, molecular formulae of C25H31ClF2O5 and molecular weight reported was 485 g/mole. Halobetasol propionate is soluble in Acetone, Acetonitrile and sparingly Soluble in Methanol, pka of 7.2 at 25 C and ph in the range of about

5 Fig Halobetasol propionate Structural formula Fusidic acid[181] is a molecule having chemical name as 2-(16- acetyloxy-3, 11 dihydroxy-4,8,10,14-tetramethyl-2,3,4, 5,6,7, 9,11,12, 13,15,16-dodecahydro- 1H- cyclopenta [a] phenanthren-17-yelidene) -6- methyl-hept-5-enoic acid. Molecular weight reported was Fusidic acid is practically insoluble in water, freely soluble in ethanol (96%) and acetonitrile. Molecular formula is C31H48O6 and it is a weak acid with a pka of 5.7. Fusidic acid is mostly ionised in tissue and plasma at the physiological ph of

6 Fig Fusidic acid Structural formula Sample selected was in solid state and complex mixture of Halobetasol propionate, Fusidic acid and other excipients. Both active ingredients are in cream formulation and which are soluble in acetonitrile and other excipients are not soluble in acetonitrile, so acetonitrile and water combination as a solvent can be selected for extraction of these drugs from cream formulation. Halobetasol propionate and Fusidic acid are having UV absorption. In summary, reverse phase chromatographic separation is suitable for method development. Columns suitable for sibutramine hydrochloride and orlistst compounds in reversed phase chromatography are C18, C8, phenyl, and cyano. 110

7 Table 3.01 Initial HPLC Method Development Conditions for Halobetasol propionate and Fusidic Acid. Separation Variable Column Preferred Initial choice Dimensions(length,ID) Particle size Stationary phase 15x0.46 cm 5 μm a C8 or C18 Mobile Phase Solvents A and B Buffer-acetonitrile % B % b Buffer(compound, concentration) ph, 25 mm potassium phosphate, 2.0<pH<3.0 c Additives(e.g.,amine modifiers, ion-pair reagents) Flow rate Not recommended initially ml/min Temperature 25 C Sample size 20 μl 111

8 3.5 EXPERIMENTAL INVESTIGATIONS: Ortho-Phosphoric Acid, AR grade, Triethylamine, AR grade, Acetonitrile, HPLC grade, Methanol, HPLC grade and Milli Q water chemicals were used for experiments. Transferred 1 ml of ortho phosphoric acid and in 1000 ml of water and adjusted ph to 3.0(±0.05) with Ortho phosphoric Acid. This solution was used as buffer in mobile phase preparation. Water and methanol were mixed in the ratio of 10: 90 v/v and this was used as diluent for standard and sample preparation Experiment No. 1 The mobile phase was acetonitrile and a solution of 0.1% phosphoric acid buffer adjusted ph to 3.0 with 10% solution of phosphoric acid, (90:10; v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, inertsil ODS-3V, 250 mm x 4.6 mm, 5 µ was maintained temperature at 25 C. The mobile phase flow rate was maintained at 1.5 ml/min. Standard Halobetasol dipropionate and Fusidic acid solution was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected two times and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. 112

9 Both the peaks eluted within 40 minutes, run time is more and forced degradation solutions are injected and found co-elution. Next experiment carried with decreased non polarity of column Experiment No.2 The mobile phase was acetonitrile and a solution of 0.1% phosphoric acid buffer adjusted ph to 3.0 with 10% solution of phosphoric acid, (30:70; v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, inertsil ODS-3V, 250 mm x 4.6 mm, 5 µ maintained temperature at 25 C. The mobile phase flow rate was maintained at 1.5 ml/min. Standard Halobetasol dipropionate and Fusidic acid solution was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected two times and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. Both the peaks eluted in 40 minutes, run time is more and forced degradation solutions are injected and found co-elution. Next experiment carried with dicresed non polarity of column. 113

10 3.5.3 Experiment No. 3 The mobile phase was acetonitrile and a solution of 0.1% phosphoric acid buffer adjusted ph to 3.0 with 10% solution of phosphoric acid, (90:10; v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, a Zorbax SB Phenyl, 250 x 4.6mm, 5 µ and maintained temperature at 25 C. The mobile phase flow rate was maintained at 1.5 ml/min. Standard Halobetasol propionate and Fusidic acid solution was prepared at concentration, 100 μg/ml of Halobetasol propionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected two times and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. Both the peaks eluted in 40 minutes, run time is more and the forced degradation solutions are injected and found to co-elution and next experiment carried with addition of amine modifers Experiment No. 4 The mobile phase was acetonitrile and a solution of 0.1% triethylamine buffer adjusted ph to 2.0 with 10% solution of phosphoric acid, (70:30; v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, Zorbax SB Phenyl, 250 x 4.6mm, 5 µ was maintained temperature at 25 C. The mobile phase flow rate was maintained at 1.5 ml/min. Halobetasol propionate and Fusidic acid 114

11 solution was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 50 μl standard solutions were injected two times and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. Both the peaks eluted in 40 minutes Halobetasol 9.2 minutes and Fusidic acid in 29.0 minutes, the forced degradation solutions are injected and found to co-elution and next experiment carried with solvent mixtures methnaol and acetonitrile Experiment No. 5 The mobile phase was acetonitrile, methanol and a solution of 0.1% phosphoric acid buffer adjusted ph to 2.0 with 10% solution of phosphoric acid, (35:13:52 v/v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, a Zorbax SB Phenyl, 250 x 4.6mm, 5 µ was maintained temperature at 25 C. The flow rate of mobile phase was maintained at 1.5 ml/min. Standard Halobetasol propionate and Fusidic acid solution was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected in duplicate and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. 115

12 All the actives and impurities are separated in dilute standard and in sample spiked impurities are not well separated and next experiment carried with fine tuning of acetonitrile and methanol Experiment No. 6 The mobile phase was acetonitrile, methanol and a solution of 0.1% triethylamine buffer adjusted ph to 2.0 with 10% solution of phosphoric acid, (35:20:45; v/v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, a Zorbax SB Phenyl, 250 x 4.6mm, 5 µ was maintained temperature at 25 C. The flow rate of mobile phase was maintained at 1.5 ml/min. Standard Halobetasol dipropionate and Fusidic acid solution was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected in duplicate and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. All the actives and impurities are separated in dilute standard and in sample spiked impurities are not well separated and next experiment carried with fine tuning of acetonitrile and methanol, wavelength was found to be suitable at 240 nm for all substances. 116

13 3.5.7 Experiment No. 7 The Final mobile phase was acetonitrile, methanol and a solution of 0.1% triethylamine buffer adjusted ph to 2.0 with 10% solution of phosphoric acid, (35:25:40; v/v/v). Mobile phase was filtered through 0.45 μ membrane filter. The analytical column, Zorbax SB Phenyl, 250 x 4.6mm, 5 µ was maintained temperature at 25 C. The flow rate of mobile phase was maintained at 1.5 ml/min. Standard Halobetasol dipropionate and Fusidic acid was prepared at concentration, 100 μg/ml of Halobetasol dipropionate and 4000 μg/ml of Fusidic acid in mobile phase. 20 μl standard solutions were injected in duplicate and average detector response measured at 240 nm. Chromatograms evaluated with respect to retention time, resolution and peak shape. All the actives and impurities are separated in dilute standard and in sample spiked impurities are not well separated and next experiment carried with fine tuning of acetonitrile and methanol, wavelength was found to be suitable at 240 nm for all substances Experiment No.8 Standard Preparation: Stock solutions 150 ppm of Halobetasol propionate, 100 ppm of diflorasone 21 propionate,100 ppm of diflorasone 17 propionate 21 mesylate, 400 ppm of Fusidic acid, 800 ppm of 3 ketofusidic acid,

14 ppm of 11 keto fusidic acid 800 ppm, 16 disacetyl fusidic acid 800 ppm were Prepared in diluent. Standard solution was prepared by mixing and diluting 1 ml each Halobetasol and its impurities solutions and 10 ml Fusidic acid, 1 ml each fusicisic acid solutions to 100 ml with diluent and obtained concentration of Halobetasol propionate 1.5 ppm, diflorasone 21 propionate1 ppm, diflorasone 17 propionate 21 mesylate 1 ppm, Fusidic acid 40 ppm, 3 ketofusidic acid 8 ppm, 11 keto Fusidic acid 8 ppm, 16 disacetyl Fusidic acid 8 ppm. Sample Preparation: Placed 5 g of sample in a 50 ml volumetric flask, added 20 ml of acetonitrile and kept on water bath at 80 C for min and then cooled to room temperature. Added 5 ml of water to the above solution and mixed well, chilled the sample solution in ice bath and finally filtered through 0.45 u Teflon filter Experiment No.9 (Method Validation) Specificity: Diluent, standard solution and sample solution of Halobetasol and Fusidic acid cream were prepared and injected into the HPLC as per methology given in Experimental Results by using a photodiode detector. 118

15 A placebo solution of Halobetasol and Fusidic cream was prepared and injected into the HPLC along with selectivity solution as per methology given in experimental results by using a photodiode array detector. The accelerated degradation conditions applied were: UV light, temperature, humidity, oxidant media, acid hydrolysis and alkaline hydrolysis. Sample were analysed against a freshly prepared control sample. The peak purity was detected by using the tools of the Waters software. Excipient solutions were submitted to the same degradation conditions in order to explain no interference. Evident details of the experiments conditions are described below: Effect of UV light: 1 ml of a solution containing 1 mg/ml of Halobetasol and 40 mg/ml of Fusidic acid in methanol was placed in a closed 1 cm quartz cell. The cells were exposed to a UV chamber 100 x 18 x 17 cm with internal mirrors and UV fluorescent lamp CRS F30W T8 emitting radiation at 254 nm for 15, 30, 60, 120 and 180 minutes. The same procedure was realized for preparation for LC analysis; samples protected in aluminum foil (in order to perotect from light) were submitted simultaneously to similar conditions and used as control. After the degradation process, the samples were diluted to 100 μg /ml of Halobetasol and 4000 μg/ml of Fusidic acid with a mixture of acetonitrile:methanol:water (6:3:1; v/v/v) and immediately analyzed. 119

16 Effect of Temperature (60 C/24 h): 5 ml of a solution containing 1 mg/ml of Halobetasol and 40 mg/ml of Fusidic acid in methanol was placed in a 10 ml volumetric flask at 60 C/24 h for 24 h. After the degradation treatment, the samples were diluted to 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid with a mixture of acetonitrile:methanol:water (6:3:1; v/v/v) and analysed immediately. Effect of Humidity (25 C/92% RH for 24 h): 5 ml of a solution containing 1 mg/ml of Halobetasol and 40 mg/ml of Fusidic acid in methanol was placed in a 10 ml volumetric flask at 25 C/92% RH for 24 h. After the degradation treatment, the samples were diluted to 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid with a mixture of acetonitrile:methanol:water (6:3:1; v/v/v) and analysed immediately. Effect of Oxidation: Halobetasol and Fusidic acid standards were dissolved in methanol (1 mg/ml of Halobetasol, 40 mg/ml of Fusidic acid and 5 ml of this solution were transferred to a volumetric flask, where hydrogen peroxide solution (30%) was added until the final concentration of 10 % and the volume was completed with methanol. After 20 hours the solution was diluted until the final concentration 100 μg/ml of Halobetasol and

17 μg/ml of Fusidic acid, filtered and analysed. Similar procedure was realized for the commercial cream, when 25 ml of the initial solution 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid, obtained as described in sample preparation for LC analysis, were transferred to a volumetric flask and submitted to degradation. A control solution containing the excipients was prepared under the same circumstances of the commercial cream. Effect of Acid Hydrolysis: 5 ml of the Halobetasol and Fusidic acid reference standard solution were transferred to a volumetric flask and HCl was added until the final concentration of 1M in both cases. After 5 hours and 1 and 6 days, one aliquot of the solution was neutralized with NaOH and diluted with acetonitrile, methanol and water (6:3:1, v/v/v) until the final concentration 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid for LC analysis. Similar procedure was realized with the commercial cream, when 25 ml of the initial solution 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid (obtained as described in sample preparation for LC analysis) were transferred to a volumetric flask and submitted to the degradation. A control solution containing the excipients was prepared under the same circumstances of the commercial cream. Effect of alkaline hydrolysis: 121

18 5 ml of the Halobetasol and Fusidic acid reference standard solution were transferred to a volumetric flask and NaOH was added until the final concentration of 1M in both cases. After 5 hours and 1 and 6 days, one aliquot of the solution was neutralized with 1M HCl and diluted with acetonitrile, methanol and water (6:3:1, v/v/v) until the final concentration 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid for LC analysis. Similar procedure was realized with the commercial cream, when 25 ml of the initial solution 100 μg/ml of Halobetasol and 4000 μg/ml of Fusidic acid were transferred to a volumetric flask and submitted to the degradation. A control solution containing the excipients was prepared under the same circumstances of the commercial cream. LOD and LOQ: The qualification and detection limits were obtained based on signalto-noise approach. The background noise was obtained after injection of the blank, observed over a distance equal to 20 times the width at halfheight of the peak in a chromatogram obtained by the injection 0.5 μg/ml of each reference standards. The signal-to-noise ratio applied was 10:1 for the LOQ and 3:1 for LOD. The results were verified experimentally. 122

19 Based on the determination of prediction linearity and visual observation of known impurities, six replicate injections were made for LOD &LOQ. Linearity and Range: To test linearity, standard plots were construted with six concentrations in the range of μg/ml of Halobetasol, μg/ml of Diflorasone 21 propionate, μg/ml of Diflorasone 17 propionate 21 MSC, μg/ml of Halobetasol propionate in triplicates. The linearity was evaluated by linear regression analysis that was calculated by the least square regression. Accuracy: The accuracy was determined by the recovery of known amounts of known impurities to the Sample in the beginning of the preparative process. The added levels were LOQ, 50, 100 and 150% of the specified limit in triplicate and then proceed with sample preparation as described under experimental result. Precision 123

20 Six replicate injections of the standard preparation were made into the HPLC used the methodology given in experimental result. Six spiked sample preparations and one control sample preparation of Halobetasol and Fusidic acid cream were prepared and injected into the HPLC using the method as described under experimental result. Ruggedness Six spiked sample preparations and one control sample preparations of Halobetasol and Fusidic acid cream were analysed by a different analyst, using different column, on different day and injected into a different HPLC using the method as described in experimental result, along with standard preparation. Robustness Standard preparation, diluent, placebo preparation and sample preparation in triplicate of the sample of Halobetasol and Fusidic acid cream were prepared as described in experimental result. The samples along with standard and placebo were injected under different chromatographic conditions. Stability of Analytical Solution 124

21 Standard solution, Sample solution were analysed initially and at different time intervals at room temperature. The system suitability was verified through the evaluation of the obtained parameters for the standard elution, such as theoretical plates, peak asymmetry and retention factor, verified in different days of the method validation. 2.6 EXPERIMENTAL RESULTS On the basis of Halobetasol and Fusidic acid Analytical method development experimental trials, RP-HPLC method was suitable for simultaneous determination of Halobetasol, Fusidic acid and their impurities. Final experiment chromatographic conditions were applied for Identification as well as quantification of related substance. Impurities were identified by spiking known impurities in to sample preparation. Preparation of stock solutions: Prepare solution having the concentration of Halobetasol 100 ppm and Fusidic acid 4000 ppm, in acetonitrile. Sample preparation: Five gram cream sample quivalent to 2.5 mg of Halobetasol and 40 mg Fusidic acid was transferred to 50 ml volumetric flask and added 20 ml of acetonitrile and kept on water bath at 80 C for min, then cooled to room temperatiure. Added 5 ml of water to this 125

22 solution and mixed well, chilled the sample in ice-bath and finally filtered through 0.45 μ Teflon filter. Separately injected equal volumes of diluent, standard preparation in six replicates and sample twice in to equilibrated HPLC system and record chromatograms and measured the response in terms of peak area. System suitability parameters occurred during method validation were Theoretical plates not less than 8000, tailing factor not more than 1.5, relative standard deviation for six replicates of standard solution is not more than 2.0%. 2.7 DISCUSSION OF RESULTS: LOD and LOQ: RSD is less than 33% at LOD level and less than 10% at LOQ level for Halobetasol and Fusidic acid and known impurities. Linearity and range: the correlation coefficients are less than for Halobetasol, Fusidic acid and known Impurities. Precision: system precision RSD is less than 5% and method precision RSD is less than 10% for Halobetasol, Fusidic acid and known Impurities. Accuracy: the mean recoveries for Halobetasol, Fusidic acid and known impurities are within %. Specificity: Retention time of Halobetasol and Fusidic acid and known peaks in sample preparation is comparable with respect to retention time 126

23 of Halobetasol and Fusidic acid and known impurities peaks in standard preparation. Peak purity passes for Halobetasol and Fusidic acid and known impurities peaksin standard and sample preparations. No intereference was observed at the retention time of Halobetasol and Fusidic acid and known impurities peaks. Peak purity passes for all degradation conditions. Ruggesness: the RSD of twelve results obtained from two different analysts are within 10 %. Robustness: Halobetasol and Fusidic acid and all known impurities peaks were resolved with each other and system suitability complies for all variable conditions, the test method is robust for all variable conditions. Stability in analytical solution: Standard and sample solutions are stable for 12 h at room temperature System suitability: Theoretical plates are less than 2000, tailing factor is less than 2.0 and relative standard deviation is less than 5.0 for six standard replicate injections. Table 3.02 Peak Purity Data for Halobetasol Propionate and Fusidic Acid Sr. No. Purity Name Criteria 127

24 Halobetasol propionate in standard solution Halobetasol propionate in sample solution Fusidic acid in standard solution Fusidic acid in sample solution Pass Pass Pass Pass Table 3.03 RT, RRT, LOD and LOQ Data of Halobetasol Propionate Impurities HBI D21PI D17P21MI HP RT RRT LOD LOQ Table 3.04 RT, RRT, LOD and LOQ Data of Fusidic Acid Impurities 11 KFA 3 KFA FA 16DAFA RT (min) RRT LOD (μg/ml) LOQ Table 3.05 Recovery Data of Halobetasol Propionate Impurities at LOQ Level Level HBI (%) D21PI (%) D17P21MI (%) HP (%) LOQ

25 LOQ LOQ Mean SD %RSD Table 3.06 Recovery Data of Halobetasol Propionate Impurities at 50, 100 and 150 % Level Level HBI (%) D21PI (%) D17P21MI (%) HP (%) Lev. 50% Lev. 50% Lev. 50% Lev. 100% Lev. 100% Lev. 100% Lev. 150% Lev. 150% Lev. 150% Avearge SD %RSD Table 3.07 Recovery Data of Fusidic Acid Impurities at LOQ Level LEVEL % Recovery 3 keto 11 keto 16 Fusidic fusidic acid fusidic acid Disacetyl acid fusidic acid LOQ LOQ LOQ Mean SD %RSD Table 3.08 Recovery Data of Fusidic Acid Impurities at 50, 100 and 150% level LEVEL % Recovery 129

26 3 keto 11 keto 16 fusidic acid fusidic acid Disacetyl fusidic acid Fusidic acid Lev. 50% Lev. 50% Lev. 50% Lev. 100% Lev. 100% Lev. 100% Lev. 150% Lev. 150% Lev. 150% Avearge SD %RSD Table 3.09 Linearity Data of Halobetasol Propionate and Impurities Diflorasone 17 Halobetasol Diflorasone 21 propionate propionate 21 MSC Halobetasol propionate Level Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area LOQ Lev. 50% Lev. 75% Lev. 100% Lev.125% Lev. 150% Lev. 200% Corr. coff R. square

27 Table 3.10 Linearity Data of Fusidic acid and Impurities Fusidic acid 3 Keto fusidic acid 11 Keto fusidic acid 16 Disacetylfusidic acid Level Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area Conc. (μg/ml) Peak area LOQ % % % % % % Corr. Coff R. square

28 Fig Halobetasol + Fusidic acid and Impurities Standard Figure 3.04 Halobetasol + Fusidic acid Cream Impurities Spiked Sample chromatograph 132

29 3.8 Summary, Conclusion and Recommenddations. A simple fast, accurate, precise, and cost effective isocratic stability indicating reverse phase high performance liquid chromatographic method was developed for simultaneous determination of Halobetasol propionate and fusidic acid as well as its impurities in the newly developed cream formulation. The chromatography equipped with Zorbax SB phenyl (250X4.6mm) column using a mobile phase of buffer 0.1% triethylamine buffer ph adjusted to 2.0 with Orthophosphoric acid acetonitrile, methanol in the ratio of 40:35:25 v/v with a flow rate of 1.5 ml/min, with UV configured at 240nm. These impurities were identified by spiking known impurities in to sample preparation. Hence this method can be conveniently adopted for routine analysis of sibutramine hydrochloride and orlistat in bulk drugs and the pharmaceutical dosage forms and also for stability analysis. 133