Novel HPLC Analysis of Hydrocortisone in Conventional and Controlled-Release Pharmaceutical Preparations.
Hydrocortisone is a naturally occurring corticosteroid hormone secreted by the adrenal cortex and released during times of stress. The synthetic drug is employed in the management of inflammatory and rheumatoid diseases, allergic conditions, and autoimmune disorders such as Addison's disease (adrenal insufficiency disease). Hydrocortisone is commercially available in pharmaceutical formulations such as tablets, capsules, creams, ointments, and injections. Hydrocortisone may exist commercially as the unchanged hormone or as the acetate, cypionate, sodium phosphate, butyrate, valerate, and the sodium succinate forms .
A search of the literature revealed that few analytical methods such as ultraviolet spectrophotometry , electrokinetic capillary chromatography [3, 4], photochemically enhanced fluorescence , thin-layer chromatography-(TLC-) densitometry [1, 6], and high-performance thin-layer chromatography (HPTLC)  have been used for the estimation of hydrocortisone in pharmaceutical formulations. However, modern chromatographic techniques such as high-performance liquid chromatography (HPLC) [8-12] and ultra-performance liquid chromatography (UPLC)  are preferentially employed for the determination of hydrocortisone in conventional pharmaceutical products such as tablets, creams, and injections. The different HPLC methods employ different chromatographic conditions including the use of complex and sometimes expensive solvent systems. Thus, access to some of these solvent systems in resource-poor countries in the developing countries can be challenging. The development of a simple and economical HPLC method using readily available reagents for the identification and quantification of hydrocortisone in pharmaceutical preparations would be an advantage in resource-poor countries.
The upsurge of autoimmune diseases such as adrenal insufficiency is a major health concern and the long-term use of conventional hydrocortisone tablets in the management of such a condition is problematic. The twice or thrice daily dosing of conventional hydrocortisone tablets to patients with adrenal insufficiency disease is incapable of mimicking the unique diurnal cortisol circadian pattern. Thus, most persons with adrenal insufficiency continue to suffer from poor therapeutic management resulting in poor quality of life and increased mortality. There is therefore the need for the development of creative and innovative treatment models for hydrocortisone replacement therapy in such dire situations. The use of controlled-release hydrocortisone oral dosage forms holds great promise with the capability to replicate the unique physiological pattern of hydrocortisone. In addition, such formulations are better able to manage and control the levels of morning androgen levels. The accurate monitoring of the quality of these promising new drug therapies is an important prerequisite to obtain quality healthcare . The improved therapy will enhance patient compliance and ensure the delivery of controlled amounts of hydrocortisone at the absorption site compared to the immediate release pattern of conventional tablets .
The aim of this study was to develop and validate a simple, sensitive, and reproducible isocratic reverse phase HPLC method with ultraviolet/visible (UV) detection capable of determination and quantification of hydrocortisone in conventional and controlled-release pharmaceutical preparations. The application of the method in determining the content of hydrocortisone in controlled-release and commercially available conventional dosage forms was also studied.
2. Materials and Methods
2.1. Standards and Reagents. The reference material of hydrocortisone (Sigma Aldrich, USA), HPLC grade methanol (Fisher Scientific, UK), glacial acetic acid (Fluka, Germany), and water (double distilled) were used. All stock and working solutions were freshly prepared with distilled water for HPLC analyses.
2.2. Hydrocortisone Pharmaceutical Preparations. Fifteen commercially available hydrocortisone pharmaceutical preparations, comprising nine tablet and six injectable formulations, were sampled from retail pharmacies within the Kumasi and Accra Metropolitan areas of Ghana. Additionally, four controlled-release hydrocortisone tablet formulations, two controlled-release capsule formulations, and one conventional release hydrocortisone tablet formulation were obtained from the Department of Pharmaceutics and Microbiology, University of Ghana School of Pharmacy, Accra, Ghana.
2.3. Instrumentation and Optimized Chromatographic Conditions. A chromatograph comprising a P100 Spectra Series pump with a 785A Programmable Perkin Elmer UV/VIS absorbance detector was employed in the study. Isocratic mode of elution was employed. Chromatographic separation was successfully achieved on a JT Baker[R] ODS C18 column (150 x 4.60 mm ID, 5 [micro]m particle size). Ultraviolet detection at a wavelength of 254 nm was able to ensure good resolution of peaks. The injection volume was 20 [micro]L and all analyses were undertaken at ambient temperature. A mobile phase consisting of methanol/water/acetic acid (60 : 30 : 10; v/v/v) at a flow rate of 1.00 ml/min was employed. All chromatographic data were acquired using PowerChrom series 280 integrator software.
2.4. Preparation of Standard Solution. Fifty milligrams of hydrocortisone reference standard was accurately weighed and dissolved in 25 ml of methanol as the diluent. The solution was transferred into a 50 ml dry volumetric flask and was then sonicated for 5 min. The volume was made up to the mark with methanol and mixed thoroughly (1 mg/ml stock solution). A one in ten (1 in 10) dilution was made to obtain a working solution with concentration of 0.10 mg/ml of hydrocortisone. This solution with the required working concentration was then injected to determine the retention time of the analyte of interest using the developed method.
2.5. Analytical Method Validation. The new HPLC method was validated in terms of linearity, limits of detection and quantification, accuracy, precision (intraday and interday), specificity, robustness, and stability, in compliance with International Conference on Harmonization (ICH) guidelines .
2.5.1. Linearity. Serial dilutions were prepared from the stock solution of hydrocortisone reference standard (1 mg/ml) by pipetting 8.0 ml, 4.0 ml, 2.0 ml, 1.6 ml, 0.8 ml, and 0.4 ml of the stock solution into separate 20 ml volumetric flasks. The solutions were made up to volume with the diluent and mixed thoroughly. Solutions prepared were injected and analyzed using the developed method. The linearity of detector response was established by plotting a graph of concentration versus peak area of hydrocortisone standard and determining the correlation coefficient.
2.5.2. Limits of Detection and Quantification. The limit of detection (LOD) and limit of quantification (LOQ) of the new HPLC method were determined from the linear regression curve obtained from the linearity of hydrocortisone. The slope and standard deviations of the responses of the linear curve were used. The formulae for the calculation of the LOD and LOQ are given below:
LOD = 3.3[delta]/S LOQ = 10[delta]/S, (1)
where [delta] is standard deviation of the response; S is slope of the calibration curve.
2.5.3. Accuracy. Into three separate 10 ml volumetric flasks 1 ml of a 1 mg/ml standard solution of hydrocortisone was pipetted. 0.8 ml, 1.0 ml, and 1.2 ml of formulated hydrocortisone solution (0.1 mg/ml) were added to the three volumetric flasks, respectively, to obtain concentrations at 80%, 100%, and 120% levels. The solutions were analyzed using the developed method. Triplicate determinations were made for each solution and mean percentage recovery calculated.
2.5.4. Precision. Both intraday and interday precision of the HPLC method were assessed. For intraday precision, three solutions of different concentrations were prepared in separate 20 ml volumetric flasks from the stock solution of hydrocortisone reference standard (1 mg/ml) by pipetting 8.0 ml, 2.0 ml, and 0.4 ml of the stock solution. Solutions were made up to volume with methanol. The various solutions where analyzed thrice during a particular day to obtain chromatograms from which recoveries and relative standard deviations (RSD) were calculated. For interday precision, a one in ten (1 in 10) dilution of the stock standard solution was prepared on three different occasions and analyzed. The solutions were analyzed on three consecutive days using the developed HPLC method to obtain chromatograms and the hydrocortisone content and relative standard deviation (RSD) were determined.
2.5.5. Specificity. The developed HPLC method was investigated for specificity to ensure there was no or minimal interference of analyte of interest from the solvent system. The mobile phase (blank) was analyzed, followed by an injection of a sample solution of hydrocortisone. After a ten-minute wash period, the blank was analyzed again.
2.5.6. Robustness. The robustness of the method was examined by introducing small changes in the composition of the mobile phase. Variation by [+ or -]10% was done with respect to the methanol component of the mobile phase while keeping the composition of the others constant. Chromatograms obtained were analyzed using the RSD of the responses obtained.
2.5.7. Stability. The stability of solutions of hydrocortisone were studied over a period of 8 hours. Triplicate injections were made each hour and the chromatograms recorded.
2.6. Assay of Hydrocortisone Preparations. An amount of finely powdered hydrocortisone powder from each of the nine commercial conventional tablet formulations equivalent to 2.5 mg hydrocortisone was individually weighed accurately and transferred to a 25 ml volumetric flask containing 10 ml of methanol. The solution was sonicated for 5 min and made up to volume with methanol. The resulting solution was then filtered using Whatman filter paper number 41. The filtrate obtained was analyzed by making triplicate injections. The controlled-release hydrocortisone tablet and capsule formulations were analyzed in a similar way. In the analysis of the hydrocortisone injections, aliquots equivalent to 2.5 mg hydrocortisone were pipetted from the six (6) injectable preparations into 25 ml volumetric flasks and treated similarly to above. The peak areas of sample were determined and the amount of hydrocortisone was estimated from the linear regression calibration curves using the developed method. The official United States Pharmacopoeia method  was employed in analyzing the commercial samples. Statistical comparison between the official and developed methods was done using Student's t-test.
3. Results and Discussion
Controlled-release hydrocortisone preparations remain formulations of choice in the therapeutic management of adrenal insufficiency disease. This disease condition is a potentially life-threatening autoimmune disorder that requires prompt diagnosis and management to avoid fatality. The use of controlled-release formulations results in more stable cortisol concentrations during the diurnal cortisol circadian pattern than conventional hydrocortisone products . It is however essential that suitable and accurate analytical methods are made available to assess the quality of the products with regard to their content. The development and validation of a simple isocratic RP-HPLC method for the determination of hydrocortisone in both conventional and controlled-release pharmaceutical formulations were the focus of this study. Review of literature indicates the employment of normal phase stationary support material [18, 19] and reverse phase stationary support material  for the development of HPLC method and further analyses of hydrocortisone products. There is yet no reported reverse phase HPLC with UV detection method capable of analyzing hydrocortisone in both conventional and controlled-release pharmaceutical formulations. The inclusion of acetic acid as a modifier in the mobile phase system ensured efficient resolution of hydrocortisone with minimal matrix effect from both conventional and controlled-release formulations. Readily available and cost effective solvents employed in the mobile phase ensured an efficient resolution and separation of hydrocortisone on a reverse phase column. Table 1 presents the optimized chromatographic conditions employed in the determination of hydrocortisone.
3.1. Analytical Method Validation. This method provides an option for the analyses of hydrocortisone in various salt forms compared to the individual methods available in some official compendia such as the United States Pharmacopoeia . The analytical method being reported gave good linear detectable responses in the range of 0.02 to 0.4 mg/ml with coefficient of correlation ([r.sup.2]) of 0.9989 with well-resolved hydrocortisone and excipient peaks (Figures 1-4). The limit of detection and limit of quantification of 1.0662 x [10.sup.-2] mg/ml and 3.23076 x [10.sup.-2] mg/ml, respectively, obtained are an indication of the sensitivity of the method. The method showed good accuracy with good recoveries in the range of 98 to 101% recorded at three concentration levels of 80%, 100%, and 120% (Table 2). The method was reproducible with good intraday and interday precision of less than 1% RSD (Tables 3 and 4). The new HPLC method showed high specificity and the robustness was less than 1% RSD (Tables 5 and 6). The method also demonstrated good stability over a period of 8 h (<6% RSD) (Table 7).
3.2. Application of Developed Method to the Analysis of Commercial Samples. Table 8 presents the characteristics, labelled strength, and assay results of conventional hydrocortisone preparations which were analyzed using both the developed HPLC method and the official USP method. Statistical analysis (t-test) of data from the two methods (official/USP and developed) showed no significant difference (p > 0.05) at a 95% confidence interval (Table 9). The analytical method developed provides a relatively cheaper alternative technique for routine postmarket analyses of hydrocortisone formulations in resource-poor countries such as Ghana. The validated method was also successfully applied to the analysis of six controlled-release hydrocortisone tablet and capsule formulations (Table 10). The application of the method in the analyses of tablets (conventional and controlled-release) and parenteral formulations indicated the versatility of the analytical procedure. The analyses of the hydrocortisone formulations yielded percentage hydrocortisone content of 95-104%, 96-103%, and 87-103% for the four controlled-release tablet formulations, two controlled-release capsule formulations, and fifteen conventional hydrocortisone formulations, respectively. All the controlled-release products were of good quality in terms of their content (percentage of content [greater than or equal to] 90%). The percentage of content of hydrocortisone powder was 100.44%. Twelve products (all 6 injections, 6 tablets) out of the 15 commercial hydrocortisone products analyzed were determined to contain the right amounts of hydrocortisone as per United States Pharmacopoeia (USP) method and the developed HPLC method . This study did not cover other pharmacopoeia specifications such as disintegration and dissolution tests.
It can be concluded that the developed and validated simple, isocratic, sensitive RP-HPLC method is useful for the determination and quantification of hydrocortisone in conventional and controlled-release pharmaceutical formulations. The method was successfully applied to commercial samples which indicate the ability of the analytical method to distinguish between good and poor quality hydrocortisone products.
Conflicts of Interest
The authors declare that there are no conflicts of interest regarding the publication of this paper.
The authors gratefully acknowledge the University of Ghana Office of Research, Innovation and Development (ORID) for providing a Faculty Development Grant to Ofosua Adi-Dako. They also appreciate the technical assistance provided by the technical staff of the Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences, KNUST, Kumasi, Ghana.
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Ofosua Adi-Dako, (1,2) Samuel Oppong Bekoe, (3) Kwabena Ofori-Kwakye, (1) Enoch Appiah, (3) and Paul Peprah (3)
(1) Department of Pharmaceutics, Faculty of Pharmacy and Pharmaceutical Sciences, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana
(2) Department of Pharmaceutics and Microbiology, School of Pharmacy, University of Ghana, Legon, Accra, Ghana
(3) Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana
Correspondence should be addressed to Kwabena Ofori-Kwakye; email@example.com
Received 7 March 2017; Accepted 26 April 2017; Published 4 June 2017
Academic Editor: Nerea Ferreiros Bouzas
Caption: Figure 1: Calibration curve of hydrocortisone showing the linear detectable range (0.02-0.4 mg/ml).
Caption: Figure 2: A chromatogram of hydrocortisone standard.
Caption: Figure 3: A chromatogram of an excipient in the hydrocortisone tablet.
Caption: Figure 4: A chromatogram of the hydrocortisone tablet.
Table 1: Optimized chromatographic conditions for the developed HPLC method. Parameters Optimized conditions Mobile phase Methanol/water/acetic acid (60 : 30 : 10, v/v/v) HPLC column JT Baker ODS C18, 5 [micro]m, 4.6 x 150 mm Flow rate 1 ml/min Wavelength detection 254 nm Diluent Methanol Injection volume 20 [micro]L Table 2: Accuracy of the HPLC method showing the mean percentage recovery of hydrocortisone at three concentration levels. Amount Amount Percentage Concentration taken added Amount recovery levels (mg/ml) (mg/ml) recovered (%) 80% 0.10 0.08 0.07820 97.75 0.10 0.08 0.07840 98.01 0.10 0.08 0.07836 97.92 100% 0.10 0.10 0.10073 100.73 0.10 0.10 0.10120 101.20 0.10 0.10 0.10052 100.52 120% 0.10 0.12 0.11998 99.98 0.10 0.12 0.12062 100.05 0.10 0.12 0.11934 99.45 Table 3: Intraday precision of proposed HPLC method showing the mean percentage recovery and RSD of hydrocortisone at different concentrations. Concentration Amount Percentage Number levels recovered * recovery of runs (mg/ml) (mg/ml) (%) % RSD 1 0.01990 99.52 2 0.02 0.01997 99.83 0.55 3 0.01975 98.76 1 0.10052 100.52 2 0.10 0.09945 99.45 0.54 3 0.10000 100.03 1 0.39952 99.88 2 0.40 0.39828 99.57 0.19 3 0.39964 99.91 * Mean of three replicate determinations. Table 4: Interday precision of proposed HPLC method showing the mean percentage recovery and RSD of hydrocortisone on different days. Percentage recovery * (%) Number of runs Day 1 Day 2 Day 3 1 100.52 98.52 100.16 2 99.45 99.67 99.51 3 100.03 98.36 99.72 Mean 100.00 98.85 99.80 % RSD 0.54 0.71 0.33 * Mean of three replicate determinations. Table 5: Results of specificity studies of the proposed HPLC method. Parameter Response Mobile phase No peak (-) Hydrocortisone Single peak obtained Mobile phase No peak (-) (-): not detected. Table 6: Robustness of proposed HPLC method showing the mean percentage content of hydrocortisone when conditions were varied. Original condition Varied condition Sample % content % content 1 100.52 101.32 2 100.75 100.65 3 101.34 99.9 Mean 100.87 100.65 % RSD 0.42 0.67 Table 7: Stability of HPLC method showing the mean recoveries of hydrocortisone in solution over an eight-hour period. Time (h) Mean concentration % RSD 0 100.72 0.56 2 100.29 0.63 4 98.40 1.73 6 95.82 3.54 8 93.11 5.79 Table 8: Characteristics and labelled strength of commercial hydrocortisone preparations analyzed using the developed HPLC method (DM) and the USP method. Dosage Country of Batch Date of Code form * Strength manufacture number manufacture HP1 PFI 100 mg Belgium 14HB24 04/2014 HP2 PFI 100 mg China 131255 12/2013 HP3 PFI 100 mg Belgium 14HB52 12/2014 HP4 PFI 100 mg India 5AB01007 10/2015 HP5 PFI 100 mg Belgium 15HB22 09/2015 HP6 PF1 100 mg India 5AE04010 10/2015 HT1 Tablet 10 mg China 150801 08/2015 HT2 Tablet 10 mg France 5EH3C 05/2015 HT3 Tablet 5 mg France 5ET4B 04/2014 HT4 Tablet 10 mg India KC004 02/2014 HT5 Tablet 5 mg India KD157 04/2015 HT6 Tablet 5 mg India KD150 04/2015 HT7 Tablet 10 mg United 13J11/C 10/2013 Kingdom HT8 Tablet 10 mg United 13J14/B 10/2013 Kingdom HT9 Tablet 10 mg United 13J12/A 08/2013 Kingdom Assay ** Assay ** Expiry (%) (%) Code date (DM) (USP) HP1 03/2017 98.41 98.60 HP2 12/2016 102.60 102.34 HP3 11/2017 100.64 100.42 HP4 09/2018 101.20 101.27 HP5 08/2018 102.80 102.83 HP6 09/2018 100.63 100.35 HT1 08/2018 86.80 86.45 HT2 05/2018 98.90 98.94 HT3 04/2017 101.55 101.72 HT4 02/2017 101.27 101.65 HT5 04/2018 87.69 87.36 HT6 04/2018 89.05 89.03 HT7 10/2016 94.38 94.27 HT8 10/2016 100.28 100.11 HT9 08/2016 98.22 98.09 * PFI = powder for injection (im/iv). ** Acceptance criterion = 90-110%. Table 9: Statistical comparison between the developed method and the USP method. USP method (column B) versus developed method (column A) t-test p value 0.9742 p value summary Ns Significantly different? (p < 0.05) No One- or two-tailed p value? Two-tailed Mean [+ or -] SEM of column A 9763 [+ or -] 1.415 N = 15 Mean [+ or -] SEM of column B 9756 [+ or -] 1.440 N = 15 Difference between means -0.06600 [+ or -] 2.019 95% confidence interval -4.202 to 4.070 Table 10: Characteristics and labelled strength of pectin-based modified release hydrocortisone preparations analyzed using the developed HPLC method. Code Dosage form Strength Assay (%) * HM1 Tablet 100 mg 103.36 HM2 Capsule 100 mg 95.99 HM3 Capsule 100 mg 103.29 HM4 Tablet 100 mg 102.41 HM5 Tablet 100 mg 104.38 HM6 Tablet 100 mg 95.34 * Acceptance criterion = 90-110 %.
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|Title Annotation:||Research Article|
|Author:||Adi-Dako, Ofosua; Bekoe, Samuel Oppong; Ofori-Kwakye, Kwabena; Appiah, Enoch; Peprah, Paul|
|Publication:||Journal of Pharmaceutics|
|Date:||Jan 1, 2017|
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