Rapid quantification of levosulpiride in human plasma using RP-HPLC-MS/MS for pharmacokinetic and bioequivalence study.

A rapid and validated method for analysis of levosulpiride in human plasma using liquid chromatography coupled to tandem mass spectrometry was developed. Levosulpiride and tiapride (IS, internal standard) were extracted from alkalized plasma samples with ethylacetate and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization in multiple-reaction monitoring mode, monitoring the transitions m/z 342.1 --> m/z 112.2 and m/z 329.1 --> m/z 213.2, for quantification of levosulpiride and IS, respectively. The standard calibration curves showed good linearity within the range of 2-200 ng/mL (r(2) > or = 0.9990). The lower limit of quantitation was 2 ng/mL. The retention times of levosulpiride (0.63 min) and IS (0.66 min) presented a significant time saving benefit of the proposed method. No significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence study of a 25 mg of levosulpiride tablet in 24 healthy Korean volunteers.

Quantification of isradipine in human plasma using LC-MS/MS for pharmacokinetic and bioequivalence study.

A highly sensitive and rapid method for the analysis of isradipine in human plasma using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed. The procedure involves a simple liquid-liquid extraction of isradipine and amlodipine (IS, internal standard) with methyl-t-butyl ether after alkaline treatment and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode, monitoring the transitions m/z 372.1-->m/z 312.2 and m/z 408.8-->m/z 237.9, for quantification of isradipine and IS, respectively. The standard calibration curves showed good linearity within the range of 10 to 5000 pg/mL (r(2)>or=0.9998). The lower limit of quantitation (LLOQ) was 10 pg/mL. The retention times of isradipine (0.81 min) and IS (0.65 min) suggested the potential for high throughput of the proposed method. In addition, no significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence studies of 5 mg of sustained-release isradipine in 24 healthy Korean volunteers.

Pharmacokinetics and bioequivalence study of two brands of loxoprofen tablets in healthy volunteers.

The aims of this study were to assess the pharmacokinetics and bioequivalence of two brands of loxoprofen (CAS 80832-23-6) 60 mg tablets in healthy male volunteers. The several pharmacokinetic parameters were evaluated after an oral administration after an overnight fast according to a single dose, two-sequence, and cross-over randomized design with a 1-week washout interval. Serial blood samples were collected throughout 10 h after administration of the reference and test drug. Plasma was analyzed by validated HPLC with UV detection. Several pharmacokinetic parameters, including AUC(infnity), AUC(t), C(max), T(max), T1/2, and Ke were determined from blood concentrations of both formulations. AUC(t), AUC(infinity) and C(max) were evaluated for bioequivalence after log-transformation of data using ANOVA with 90% confidence interval level. The parametric 90% confidence intervals of AUC(t), AUC(infinity), and C(max) were 90.13-106.34%, 91.43-106.94%, and 91.17-108.53%, respectively. All of the tested parameters were within the acceptable range of 80-125%. Based on these statistical considerations, it was concluded that the test drug was bioequivalent to the reference drug.

Determination of paroxetine in plasma by liquid chromatography coupled to tandem mass spectrometry for pharmacokinetic and bioequivalence studies.

A rapid and validated liquid chromatography coupled to tandem mass spectrometric method (LC-MS-MS) has been developed and applied to pharmacokinetic and bioequivalence studies in 24 healthy male Korean volunteers. The procedure involves a liquid-liquid extraction of paroxetine (CAS 61869-08-7) and fluoxetine (internal standard, CAS 54910-89-3) with ether/methyl chloride (7:3, v/v) and separated by LC equipped with C18 column using acetonitrile: 5 mmol/L ammonium formate (4:3, v/v) as mobile phase. Detection is carried out on an API 2000 MS system by multiple reactions monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved by MS-MS analysis, mlz 330.0-->192.0 and m/ z 310-->148 for paroxetine and fluoxetine, respectively. The method has a total run time of 1.5 min and was linear over a working range of 0.05-20 ng/mL and the lower limit of quantification was 0.05 ng/ mL. No endogenous compounds were found to interfere with the analysis. The inter-day and intra-day accuracy was in the ranges of 102.69-107.79% and 102.07-109.57%, respectively and precision of inter-day and intra-day expressed as relative standard deviation were 1.86-9.99% and 1.52-6.28%, respectively. The validation of this method on linearity, specificity, accuracy, precision as well as applicability to pharmacokinetic and bioequivalence studies by analysis of blood samples taken up to 72 h after oral administration of 20 mg of paroxetine in 24 healthy volunteers were found to be good performance.

Validated LC-MS/MS method for quantification of gabapentin in human plasma: application to pharmacokinetic and bioequivalence studies in Korean volunteers.

A sensitive validated liquid chromatography-tandem mass spectrometric method (LC-MS/MS) for gabapentin (GB) in human plasma has been developed and applied to pharmacokinetic (PK) and bioequivalence (BE) studies in human. In a randomized crossover design with a 1-week period, each subject received a 300 mg GB capsule. The procedure involves a simple protein precipitation with acetonitrile and separated by LC with a Gemini C(18) column using acetonitrile-10 mm ammonium acetate (20:80, v/v, pH 3.2) as mobile phase. The GB and internal standard [(S)-(+)-alpha-aminocyclohexanepropionic acid hydrate] were analyzed using an LC-API 2000 MS/MS in multiple reaction monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved using MS/MS analysis, m/z 172.0 --> 154.0 and m/z 172.0 --> 126.0 for GB and IS, respectively. The assay exhibited good linearity over a working range of 20-5000 ng/mL for GB in human plasma with a lower limit of quantitation of 20 ng/mL. No endogenous compounds were found to interfere with the analysis. The accuracy and precision were shown for concentrations over the standard ranges. This method was successfully applied for the PK and BE studies by analysis of blood samples taken up to 36 h after an oral dose of 300 mg of GB in 24 healthy volunteers.

Pharmacokinetic and bioequivalence evaluation of two formulations of 100 mg trimebutine maleate (Recutin and Polybutin) in healthy male volunteers using the LC-MS/MS method.

BACKGROUND: Trimebutine maleate is a prokinetic agent that acts directly on the smooth muscle of the GI tract. A bioequivalence (BE) study of 2 oral formulations of 100 mg trimebutine maleate (TMB) was carried out in 24 healthy male Korean volunteers according to a crossover-randomized design. METHODS: Subjects were given a single dose of 2 100 mg tablets of each formulation. The test and reference formulations were Recutin (Hutax Co., South Korea) and Polybutin (Samil Co., South Korea), respectively. Each set of tablets was administered with 240 ml of water to subjects after 10 h overnight fasting on 2 treatment days separated by a 1 week washout period. After dosing, serial blood samples were collected for a period of 36 h. Plasma was analyzed for the main metabolite of TMB, N-monodesmethyl trimebutine (nor-TMB), by a validated LC with MS/MS detection capacity for nor-TMB in the range 5-1500 ng/ml, with a lower limit of quantification (LLOQ) of 5 ng/ml. Several pharmacokinetic (PK) parameters (including AUC(t), AUC(infinity), C(max), T(max), T(1/2), and K(e)) were determined from the plasma concentrations of nor-TMB of both formulations. AUC(t), AUC(infinity), and C(max) were tested for BE after log-transformation of the data. RESULTS: No significant difference was found based on ANOVA; 90% confidence intervals (98.98%112.03% for AUC(t); 98.60%-113.20% for AUC(infinity); 90.85%-107.87% for C(max)) for the test and reference were found within KFDA acceptance range of 80-125%. CONCLUSIONS: Based on these statistical inferences, it was concluded that Recutin is bioequivalent to Polybutin and can be used interchangeably in a clinical setting.

Quantitative analysis of tiropramide in human plasma by gas chromatography coupled to mass spectrometry for application to a bioequivalence test.

BACKGROUND: Tiropramide is used as an antispasmodic agent. A sensitive, selective and simple gas chromatography coupled to mass spectrometry (GC/MS) was developed for quantification of tiropramide in human plasma using internal standard (ISD, (+/-) alpha-benzoylamino-4-[2-(dimethylamino) ethoxy]-N,N-dipropylbenzenepropanamide). METHODS: Tiropramide and ISD were extracted from plasma by solid-liquid extraction and analyzed on a HP-5MS column with mass selective detector. RESULTS: The retention times of tiropramide and ISD were approximately 9.8 and 10.2 min, respectively. The calibration curve showed good linearity in the concentration range 5-500 ng/ml (r2=0.998) for tiropramide in human plasma and showed good precision with CVs between 0.24% and 7.69%, respectively. The method was showed good accuracy with all intra-day (n=5) and inter-day (n=5) mean concentrations within 87.9-114.1% from nominal. The recovery of tiropramide and ISD were about 75.1% and 71.0% on the average, respectively. This method was successfully applied for the bioequivalence test of 2 formulations of tiropramide in 18 healthy male volunteers who received a single 100 mg dose of each formulation.