Single Dose Study Assessing the Pharmacokinetic and Metabolic Profile of Alverine Citrate in Healthy Volunteers

Alverine citrate is a spasmolytic commonly prescribed in conditions such as irritable bowel syndrome, painful diverticular disease of the colon, and primary dysmenorrhea. While clinical efficacy data on alverine alone or in combination with simethicone is freely available, surprisingly little information regarding the pharmacokinetics and metabolism of alverine can be found in literature. The first HPLC-MS/MS analytical protocol for determination of alverine parent, 4-hydroxy alverine, N-desethyl alverine and 4-hydroxy alverine glucuronide in human plasma was developed and validated. The two validated methods were used for analyzing plasma samples collected during an open label, non-comparative, single dose, one-period, one-treatment, pharmacokinetic and metabolic profile study of Spasmonal^® Forte 120 mg hard capsule, conducted in 12 fasting healthy male and female volunteers of Caucasian descent. The study confirmed previous suspicions that parent alverine is subject to high pharmacokinetic variability and also revealed that the metabolic process most susceptible to outlying performance in Caucasians is hydroxylation to the active metabolite 4-hydroxy alverine. Another interesting observation made is that alverine parent accounts for only 3%, whereas total 4-hydroxy alverine (free and conjugated) accounts for 94% of alverine-related moieties in circulation (based on comparisons of total exposure).

An improved LC-MS/MS method for the quantification of alverine and para hydroxy alverine in human plasma for a bioequivalence study☆

A highly sensitive and selective high performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of alverine (ALV) and its active metabolite, para hydroxy alverine (PHA), in human plasma. For sample preparation, solid phase extraction of analytes was performed on Phenomenex Strata-X cartridges using alverine-d5 as the internal standard. The analytes were separated on Symmetry Shield RP₁₈ (150 mm×3.9 mm, 5 µm) column with a mobile phase consisting of acetonitrile and 10 mM ammonium formate (65:35, v/v). Detection and quantitation was done by electrospray ionization mass spectrometry in the positive mode using multiple reaction monitoring. The assay method was fully validated over the concentration range of 15.0–15,000 pg/mL for ALV and 30.0–15,000 pg/mL for PHA. The intra-day and inter-day accuracy and precision (% CV) ranged from 94.00% to 96.00% and 0.48% to 4.15% for both the analytes. The mean recovery obtained for ALV and PHA was 80.59% and 81.26%, respectively. Matrix effect, expressed as IS-normalized matrix factor ranged from 0.982 to 1.009 for both the analytes. The application of the method was demonstrated for the specific analysis of ALV and PHA for a bioequivalence study in 52 healthy subjects using 120 mg ALV capsules. The assay reproducibility was also verified by reanalysis of 175 incurred subject samples.

Determination of pregabalin in human plasma by electrospray ionisation tandem mass spectroscopy

A rapid, precise, specific, and accurate Electrospray Ionisation Tandem Mass Spectrometry (ESI-MS / MS) method has been developed and subsequently validated, for the determination of pregabalin (PB) in human plasma. Gabapentin (GB) was used as the internal standard. PB and GB were extracted from the plasma using a combination of deproteinization, using 0.1% formic acid and liquid-liquid extraction, using methylene chloride. PB and GB were separated using the Hypurity advance column (50 mm × 4.6 mm, 5 μm) and mobile phase, consisting of methanol : 0.1% formic acid (80:20 v / v). PB was determined by using ESI-MS / MS in positive ion mode, with the help of the API 2000 spectrophotometer, operated in a multiple reaction monitoring mode. The parent-to-product ion combination of m / z 160.2→55.1 and 172.2→95.0 was used to quantify PB and GB, respectively. The assay was validated in the concentration range of 99.79 - 4019.90 ng / mL for PB. The limit of quantification (LOQ) was identifiable and reproducible at 99.79 ng / mL. The method has been successfully applied to study the pharmacokinetics of PB in healthy male volunteers.

Simultaneous estimation of atorvastatin and its two metabolites from human plasma by ESI-LC-MS/MS

A selective, sensitive, and fast high performance liquid chromatography (HPLC) method with mass spectrometric (MS) detection mode has been developed and validated completely in human plasma. Atorvastatin (ATO), p-hydroxy atorvastatin (p-HATO), o-hydroxy atorvastatin (o-HATO) and internal standard (IS) are extracted from human plasma via solid phase extraction (SPE) technique. After elution, the solution is evaporated, then reconstituted with 250 µL of Mobile Phase and analyzed using HPLC/MS/MS system. An isocratic mode is used to separate interference peaks using a Symmetry C-18, 75 × 4.6 mm ID, 3.5 µ, column. The m/z of ATO, o-HATO and p-HATO are 559.2/440.2, 575.3/440.4 and 575.0/440.4 respectively. Linearity ranges are 0.05 to 252.92 ng/mL for ATO, p-HATO and o-HATO respectively. Calibration functions, lower limit of quantitation (LLOQ), stability, intra- and inter-day reproducibility, accuracy, and recovery are estimated. This method is free from matrix effects and any abnormal ionization. This method was successfully applied to a single dose 80 mg tablet bioequivalence (BE) study of Atorvastatin. Copyright © 2011 John Wiley & Sons, Ltd.