Determination of propranolol in dog plasma by HPLC method

Transcription

1 Asian Journal of Pharmacodynamics and Pharmacokinetics Paper ID Copyright by Hong Kong Medical Publisher Received December 30, 2007 ISSN ; 8(2): Accepted April 10, 2008 Determination of propranolol in dog plasma by HPLC method Shuhua Xiao, Guangli Wei, Hong Guo, Heng Liu, Changxiao Liu* Tianjin Key Laboratory of Pharmacokinetics and Pharmacodynamics, Tianjin Institute of Pharmaceutical Research, Tianjin , P.R.China Abstract Key words A rapid, sensitive and accurate high performance liquid chromatographic (HPLC) method for determination of propranolol in dog plasma is described. Propranolol was extracted from dog plasma using a mixture of n-heptane and isoamyl alcohol (98.5:1.5, v/v) and separated on a C18 column. The mobile phase consisting of a mixture of acetonitrile- water (containing of 1% acetic acid and 0.2 % of triethylamine) (28:72, v/v) was delivered at a flow rate of 0.9 ml/min. Linearity was obtained over the concentration range of ng/ml for propranolol and the lower limit of quantitation was 2.0 ng/ml. For each level of QC samples, inter- and intra-run precision was less than 4.3% and 5.5% (relative standard deviation (R.S.D.), respectively, and the bias was within ±4.0%. This method was successfully applied to the pharmacokinetic study of a propranolol formulation after oral administration to Beagle dog s. Propranolol; high performance liquid chromatographic method. Introduction Propranolol, a β-adrenergic receptor blocking agent, is widely used as the commercially available racemic mixture in the treatment of hypertension, thyrotoxicosis,cardiac arrhythmias, and other diseases [1]. There are several methods presently available to measure propranolol in biological fluids [2-7]. However, some of these methods require laborious work-up, lack an internal standard in the assay, and some others require large sample volumes to obtain a reasonable detection limit [2-7].we have developed a simple, specific and highly sensitive HPLC method for the determination of propranolol in dog plasma. The method only require 0.5ml of plasma to obtain a lower detetion limit of 2.0ng/ml. The described method was validated in terms of selectivity, sensitivity, linearity, accuracy, precision and stability of analyte in dog plasma and successfully applied to the pharmacokinetic studies of a propranolol formulation in dogs. Experimental Chemicals and reagents Propranolol (purity, 99.5%), propranolol capsules (120.0 mg, batch no ) and Metoprolol (purity, 99.7%, internal standard, IS) were supplied by Tianjin Institute of Pharmaceutical Research (Tianjin, China). HPLC-grade methanol, acetonitrile and n-heptane were all purchased from Tianjin Concord Tech Reagent Company (Tianjin, China). Isoamyl alcohol, analytical-grade, was purchased from Tianjin Chemical Reagent Hong-yan Factory (Tianjin, China). Acetic acid, analytical-grade, was purchased from Tianjin Chemical Reagent Tian-he Factory (Tianjin, China). Sodium hydroxide (NaOH), triethglamine, analytical-grade, was purchased from Tianjin Chemical Reagent Factory (Tianjin, China). Water was purified with a SYZ 550 quartz pure water distiller ( Tianjin Xinzhou Tech Co. Ltd., China). Instrumentation The liquid chromatographic system consisted of a Shimadzu LC-10A series liquid chromatograph (including SCL-10A system controller, SIL-10AXL auto injector, LC-10AT pump, thermostated column compartment) with a fluorescence RF-10AXL detector. 153

2 The system runs by ChemStation software. Chromatographic conditions Chromatographic separation was performed on a Diamonsil C18 column (200mm 4.6mm i.d., 5μm, Dikma Technologies, China). The mobile phase consisting of a mixture of acetonitrile-water (containing of 1% acetic acid and of 0.2% triethylamine) (28:72, v/v) was delivered at a flow rate of 0.9 ml/min. The column temperature was maintained at 40. The injection volume was 50 μl. Preparation of calibration standards and quality control samples Stock solutions of propranolol and IS were individually prepared at 1mg/ml in methanol. They were stable at least for one month at 4. The stock solution of propranolol was further diluted with methanol to give a series of standard solutions with concentration of 0.1, 1, 10.0 and μg ml -1. In order to prevent photodegradation, all solutions of propranolol were stored in brown volumetric flask in the dark. A solution containing μg ml -1 IS was also prepared using methanol. Calibration standards of propranolol (2.0, 5.0, 20.0, 50.0, and ng ml -1 ) were prepared by spiking appropriate amount of the standard solutions in blank dog plasma. Quality control (QC) samples were prepared using the pooled dog plasma at concentrations of 5.0, 50.0 and ng/ml. The spiked samples were then treated using the sample preparation procedure as indicated in below. Sample preparation 50 μl of IS (100.0 μg/ml) was added to 500 μl plasma sample. Each sample was further added 100 μl of 0.25 M NaOH (Sodium hydroxide) and 3 ml of n-heptane-isoamyl alcohol (98.5:1.5,v/v), the mixture were vortexed for 1 min and centrifuged at 2500 g for 5 min, then 2.25 ml organic layer was transferred to a glass tube and dried with nitrogen in a 40 water bath. The residue of each sample was reconstituted in 150μl of the mobile phase, and a 50 μl aliquot was injected onto the HPLC system. Method validation Validation runs were conducted on three separate days. Each validation run consisted of a set of the spiked standard samples at six concentrations over the concentration range (each in triplicate), QC samples at four concentrations (n = 4, at each concentration), blank samples. Standard samples were analyzed at the beginning and the end of each validation run and other samples were distributed randomly throughout the run. The results from QC samples in three runs were used to evaluate the accuracy and precision of the method developed. Concentrations of the analyte in plasma samples were determined by back-calculation of the observed peak-area ratios of the analyte and IS from the best-fit calibration curve using a weighted (1/x 2 ) linear regression. During routine analysis, each analytical run included a set of standard samples, a set of QC samples in duplicate and plasma samples to be determined. The extraction recovery of propranolol was determined at low, medium and high concentrations by comparing the responses from plasma samples with those from standard solutions. In both cases, the IS was added after extraction to eliminate bias introduced by the sample processing. To test sample stability stored under different conditions, three levels of QC samples, containing low (5.0 ng ml -1 ), medium (50.0 ng ml -1 ), and high (200.0 ng ml -1 ) concentrations, were analyzed. The stabilities of samples after 3 freeze and thaw cycles (by thawing at room temperature for 1 2 h and freezing for h), short-term storage at room temperature for 16 h, long-term storage at 20 for 15 days and hold in autosampler for 16h were determined. Application of the HPLC method The HPLC method developed was successfully applied to the pharmacokinetic studies of a propranolol formulation in dogs. Six Beagle dogs were given a single oral dose of propranolol capsules (120.0 mg). Food was allowed 0.5 h before oral administration, while water intake was controlled. Blood (3.0mL) was collected into heparinized tubes before (0 h) and at 2, 3, 4, 5, 6, 8, 10, 11, 12, 14, 16, 18, 20, 22 and 24 h after dosing. Plasma was separated by centrifugation and immediately shielded from light and kept frozen at 20 until analysis. Results and discussion Method development Liquid liquid extraction (LLE) was used for the sample preparation in this work. LLE can be helpful in 154

3 producing a clean sample and avoiding the introduction of non-volatile materials onto the column and HPLC system. Finally, n-heptane- Isoamyl alcohol (98.5:1.5) was found to be optimal, which can produce a clean chromatogram for a blank plasma sample and yield the highest and stable recovery for the analyte from the plasma. Adding a little amount of isoamyl alcohol can prevent from emulsification caused by only using n-heptane as extract solvent. The chromatographic conditions, especially the composition of mobile phase, were optimized through several trials to achieve good resolution and symmetric peak shapes of analytes as well as short run time. Finally, a mixture of acetonitrile, water (contain acetic acid of 0.1% and triethglamine of 0.2%) (28:72, v/v) was adopted as the mobile phase. The optimal wavelength of excitation (EX) and emission (EM) were 296 and 340 nm for propranolol [7], 277 and 299 nm for metoprolol [8], respectivety. In order to ensure the analyte detection limit and IS determineation of the same time, the detection were length of EX and EM were optimized to 285 and 330 nm.clean chromatograms were obtained and no significant matrix effect was found. A rapid, sensitive and accurate HPLC method was developed for the determination of propranolol in dog plasma. The method was successfully applied to the pharmacokinetic studies of a propranolol formulation in dogs. Specificity The specificity of the method was investigated by comparing chromatograms of six different sources of dog plasma. The HPLC chromatograms of the propranolol in Fig. 1. indicating no interferences from endogenous substances in dog plasma with the analyte and IS. Propranolol and IS exhibited retention times of 8.9 and 4.1 min, respectively. A highly specific assay for propranolol was developed. A IS B S C IS D IS S S Fig.1. HPLC chromatograms of the propranolol and IS A-standard; B-blank dog plasma C- blank dog plasma spiked with propranolol 50.0ng ml -1 and IS 100.0μg ml -1 D- plasma 5.0 h after a single oral dose of 120 mg propranolol to a dog S- propranolol IS-internal standard Linearity and sensitivity The linearity of each calibration curve was determined by plotting the peak-area ratio (y) of propranolol to IS versus the nominal concentration (x) 155

4 of propranolol. The calibration curves were obtained by weighted (1/x2) linear regression analysis. To evaluate the linearity of the HPLC method, plasma calibration curves were determined in triplicate on three separate days. Representative regression equation for the calibration curve was y = x (x unit:ng/ml) with a correlation coefficient of Good linearity was observed over the concentration range of ng/ml for propranolol. The lower limit of quantitation (LLOQ) for determination of propranolol in dog plasma was 2.0ng/ml (with an accuracy less than ±4.8% and a precision less than 4.7%), which is sufficient for pharmacokinetic study of propranolol in dogs. Accuracy and precision The accuracy and precision of the method were evaluated based on the data from QC samples in three validation runs. The accuracy was determined by calculating the percentage deviation observed in the analysis of QC samples and expressed as bias. The intra- and inter-run precision was expressed as the relative standard deviation. As shown in Table 1, for each QC level of propranolol, the intra and inter-run precision was less than 5.5% and 4.3%, respectively, and the accuracy was within ±4.0%, indicating the acceptable accuracy and precision of the method developed. Table 2 Extraction recovery of propranolol and metoprolol (internal standard) in dog plasma (n = 5) Concentration (ng/ml ) Extraction recovery (%, Mean±S.D.) Propranolol ± ± ±7.0 Metoprolol 92.1±2.9 Table 1 Accuracy and precision for the determination of propranolol in dog plasma (n = 3 days, five replicates per day) Nominal Conc. (ng/ml) Batch n Calculated Conc. (ng/ml) S.D Relative std dev. (%) a Bias (%) Intra-run R.S.D. a (%) Inter-run R.S.D. (%) a: Relative standard deviation. 156

5 Extraction recovery The extraction recovery of propranolol from dog plasma was determined by comparing peak areas from plasma samples with those from standard soluteions. Table 2 showed that the mean extraction recoveries of propranolol from dog plasma were all above 86% at the concentration range of ng/ml and that of IS was 92.1%. Stability The stability of propranolol in dog plasma and mobile phase were investigated. As shown in Table 3, propranolol in dog plasma was found to be stable after 15 days storage at -20, three freeze thaw(-20 / room temperature) cycles and at room temperature for at least 16 h. Propranolol in the reconstitution mobile phase was also found to be stable for at least 16 h at room temperature. The change of the analyte was less than 0.9% at concentrations of 5.0, 50.0 and ng/ml, respectively. Table 3 Stability for the determination of propranolol in dog plasma (n = 3) Conditions Nominal Conc. (ng/ml) Calculated Conc. (ng/ml) R. S. D. (%) at ambient temperature for 16h reconstituted at ambient injector for 16h for 15 days freeze-thaw cycles Bias (%) Concentration(C,ng/ml) Time(h) Fig. 2. Mean plasma concentration time profiles of propranolol after oral administration of propranolol capsules (120.0 mg) to six dogs Application The HPLC method developed for the determination of propranolol in dog plasma has been successfully applied to the pharmacokinetic study of a 157

6 propranolol formulation following oral administration to six dogs. The mean plasma concentration time profiles for propranolol capsules are shown in Fig. 2. The highest concentration of propranolol in dog plasma was observed at h after an oral dose of 120.0mg. The C max, AUC 0-24h and t 1/2βwere (51.3± 27.2) ng/ml, (411.8±201.7) ng h/ml and (5.1±1.5) h, respectively. Conclusions A rapid, sensitive and accurate HPLC method was developed for the determination of propranolol in dog plasma. The method was successfully applied to the pharmacokinetic studies of a propranolol formulation in dogs. Acknowledgement This work was supported by the Tianjin Science and Technology Development Program of China (Grant number 06YFGZSH 01400). References 1. Garg DC, Jallad, MS, et al. Comparative pharmacodynamics and pharmacodynamics of conventional and long-acting propranolol. J Clin Pharmacol, 1987,27: Koshakji RP, Wood AJ. A modified, sensitive liquid chromatographic method for measurement of propranolol with fluorescence detection.j Pharm Sci Jan;75(1): Harrison PM, Tonkin AM, Cahill CM, McLean AJ. Rapid and simultaneous extraction of propranolol, its neutral and basic metabolites from plasma and assay by high-performance liquid chromatography. J Chromatogr Oct 11;343(2): Hermansson J, Grahn A, Hermansson I. Direct injection of large volumes of plasma/serum on a new biocompatible extraction column for the determination of atenolol, propranolol and ibuprofen. Mechanisms for the improvement of chromatographic performance. J Chromatogr A Feb 27;797(1-2): Semple HA, Xia F. Simplified high-performance liquid chromatographic method for propranolol and five metabolites in liver perfusate, rat serum and dog plasma. J Chromatogr B Biomed Appl May 13;655(2): Prakash C, Koshakji RP, Wood AJ, Blair LA. Simultaneous determination of propranolol enantiomers in plasma by high-performance liquid chromatography with fluorescence detection. J Pharm Sci Sep;78(9): Guangli Wei, Shuhua Xiao, Changxiao Liu,al. Comparion of bioavailability of propranolol hydrochloride ordinary and sustained-release tablets. Acta Pharmaceutica Sinica 1999,34(8): Wang Jing, Fu Liang-qing, Guan yong-biao, et al. Bioequivalence of metoprolol tartarte tablets in healthy volunteers. Chin J Clin Pharmacol Ther 2006,11(9): *Correspondence to Prof. CX Liu, State Key Laboratory of Pharmacodynamics and Pharmacokinetics, Tianjin Institute of Pharmaceutical Research, Tianjin, , China liuchangxiao@vip.163.com 158