A validated enantioselective LC–MS/MS assay for the simultaneous determination of carvedilol and its pharmacologically active 4′-hydroxyphenyl metabolite in human plasma: Application to a clinical pharmacokinetic study

Supported liquid extraction combined with liquid chromatography tandem mass spectrometry for the quantitative analysis of a TLR7 agonist imiquimod LFX453 in plasma at low picograms per milliliter: Method validation and its application to a pharmacokinetic study in minipig

Sample preparation is essential for low-level compound determination. In the present work, supported liquid extraction (SLE) was used as sample preparation for the low-level determination of a new TLR7 agonist imiquimod compound, LFX453. Samples were extracted on ISOLUTE® SLE 96-well plates using tert-butyl-methyl ether followed by evaporation and dry residue reconstitution with 150 μl of a mixture of 0.1% formic acid in acetonitrile-water (50/50, v/v). Samples were eluted using a flow rate of 0.750 ml/min on a C18 column (50 × 2.1 mm, 2.7 μm) with a mobile phase consisting of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). Tandem mass spectrometry was used to analyze the samples in positive mode. The method run time was 6.5 min, and the low limit of quantification was 1.00 pg/ml with 0.100 ml of minipig plasma. Intra-run and inter-run precision and accuracy were within the acceptance criteria at four concentration levels over a concentration ranging from 1.00 to 200 pg/ml. There was no matrix effect and recovery, three freeze-thaw cycles and incurred samples reanalysis were validated. The method was successfully applied for measuring LFX453 in minipig plasma after application on minipig skin.

Enantioselective binding of carvedilol to human serum albumin and alpha-1-acid glycoprotein

Carvedilol, a highly protein-bound beta-blocker, is used in therapy as a racemic mixture of its two enantiomers that exhibit different pharmacological activity. The aim of this study was to evaluate the stereoselective nature of its binding to the two major plasma proteins: albumin and alpha-1-acid glycoprotein. The determination of the plasma protein-binding degree for carvedilol and its enantiomers was achieved using ultrafiltration for the separation of the free fraction, followed by LC-MS/MS quantification, using two different developed and validated methods in terms of stationary phase: achiral C18 type and chiral ovomucoid type. Furthermore, molecular docking methods were applied in order to investigate and to better understand the mechanism of protein-binding for S-(-)- and R-(+)-carvedilol. A difference in the binding behavior of the two enantiomers to the plasma proteins was observed when taken individually, with R-(+)-carvedilol having a higher affinity for albumin and S-(-)-carvedilol for alpha-1-acid glycoprotein. However, in the case of the racemic mixture, the binding of the S enantiomer to alpha-1-acid glycoprotein seemed to be influenced by the presence of its antipode, although no such influence was observed in the case of albumin. The results raise the question of a binding competition between the two enantiomers for alpha-1-acid glycoprotein.

UHPLC Enantiomer Resolution for the ɑ/β-Adrenoceptor Antagonist R/S-Carvedilol and Its Major Active Metabolites on Chiralpak IB N-5

Carvedilol (CAR), a racemic lipophilic aryloxy propanolamine, acts as a selective α₁-adrenoreceptor antagonist and a nonselective β-adrenoreceptor antagonist. CAR metabolism mainly produces three active metabolites: desmethyl carvedilol (DMC), 4'-hydroxy carvedilol (4'OHC) and 5'-hydroxy carvedilol (5'OHC). The oxidative S-(-)-metabolites contribute to the β-antagonistic effect, yet not to the α-antagonistic effect to be observed after drug dosage. Therefore, the three β-adrenoceptor blocking metabolites, which are structurally closely related to the parent CAR, are included into the development of a bioanalytical quantitative method for all major active species relevant with respect to adrenoceptor-blockade. Because of the given pharmacological profile, resolution of the enantiomers of carvedilol, of 4'- and 5'-hydroxy carvedilol as well as of DMC, is mandatory. The current study aims to determine the response surface for the enantiomer separation of the parent CAR as well as the major metabolites on a suitable chiral stationary phase. Design of experiment approach (DoE) was utilized in an initial screening phase followed by central-composite design for delimitation of the response surface for resolution of the four enantiomeric pairs in least run time. The impact of chromatographic variables (composition and percentage of organic modifier(s), buffer type, buffer pH, flow rate) on critical peaks resolution and adjusted retention time was evaluated, in order to select the most significant critical quality attributes. On this basis, a robust UHPLC-UV method was developed and optimized for the simultaneous, enantioselective determination of CAR along with its major active metabolites (4'OHC, 5'OHC, and DMC) on Chiralpak IBN-5. The optimized UHPLC-UV method (which includes metoprolol as the internal standard) was validated according to the ICH M10 guidelines for bioanalytical methods and proven to be linear, precise, accurate, and robust. The validated assay was applied to plasma samples from cardiovascular patients treated with rac-CAR (blood randomly drawn at different times after oral CAR intake). In order to provide more insight into the mechanism of the enantiomer separation of CAR and its metabolites on the CSP, docking experiments were performed. Molecular simulation studies suggest the chiral recognition to be mainly due to different binding poses of enantiomers of the same compound.

Chemometric optimization of salting-out assisted liquid-liquid extraction (SALLE) combined with LC-MS/MS for the analysis of carvedilol enantiomers in human plasma: Application to clinical pharmacokinetics

Carvedilol is a commonly used antihypertensive whose oral absorption is limited by low solubility and significant first-pass metabolism. This work aimed to apply chemometrics for the optimization of a salting-out assisted liquid-liquid extraction (SALLE) combined with LC-MS/MS to analyze carvedilol enantiomers in plasma samples. Method development and validation were driven for application in pharmacokinetic studies. Parameters that influence the efficiency of SALLE were evaluated using a fractional factorial 24-1 design with 4 factors and a central composite design was used to evaluate the optimal extraction condition. Carvedilol enantiomers and the internal standard lidocaine were separated on an Astec® Chirobiotic® V column and a mixture of methanol:ethanol (90:10, v/v) with 0.02% diethylamine and 0.18% acetic acid as mobile phase. The positive ion mode on electrospray ionization was used to monitor the transitions of m/z 407 > 100 and 235 > 86 for carvedilol enantiomers and lidocaine, respectively. Acetonitrile and ammonium acetate solution were selected for sample preparation by SALLE. Surface graphs and the desirability test were used to define the optimized SALLE conditions which resulted in 93% recovery for both carvedilol enantiomers. The method was linear in the range of 0.5 to 100 ng/mL in plasma, with a lower limit of quantification of 0.5 ng/mL. Within-run and between-run precision (as the relative standard deviation) were all < 9.74% and accuracy (as relative error) did not exceed ± 10.30%. Residual effect and matrix effect were not observed. Carvedilol enantiomers were stable in plasma under the storage, preparation, and analysis conditions. The validated method was successfully applied to analyze carvedilol in plasma samples from patients previously submitted to a Roux-en-Y gastric bypass surgery treated with a single oral dose of 25 mg racemic-carvedilol. Higher plasma concentrations were observed for (R)-(+)-carvedilol when compared to (S)-(-)-carvedilol in two patients post-bariatric surgery.

Hollow fiber based liquid phase microextraction with high performance liquid chromatography for the determination of trace carvedilol (β-blocker) in biological fluids

A hollow-fiber liquid-phase microextraction (HF-LPME), followed by high-performance liquid chromatography–ultraviolet (HPLC–UV) method for the trace determination of carvedilol (β-blocker) in biological fluids, has been described. The separation was achieved using Inertsil ODS-3 C18 (250 mm × 4.6 mm, 3 μm) column with a mobile phase composition of 10 mM phosphate buffer (pH 4.0)–acetonitrile (50:50, v/v) at a flow rate of 1.0 mL/min, under isocratic elution. Several parameters (i.e., type of organic solvent, donor phase pH, concentration of acceptor phase (AP), stirring rate, extraction time, and salt addition) that affect the extraction efficiency were investigated. The optimum HF-LPME conditions were as follows: dihexyl ether as an organic solvent; donor phase pH, 10.7; 0.1 M HCl (AP); 1100-rpm stirring rate; 60-min extraction time; and no salt addition. These parameters have been confirmed using design of experiments. Under these conditions, an enrichment factor of 273-fold was achieved. Good linearity and correlation coefficient were obtained over the range 5–1000 ng/mL (r2 = 0.9994). Limits of detection and quantitation were 1.2 and 3.7 ng/mL, respectively. The relative standard deviation at 3 different concentration levels (5, 500, and 1000 ng/mL) were less than 13.2%. Recoveries for spiked urine and plasma were in the range 80.7–114%. The proposed method is simple, sensitive, and suitable for the determination of carvedilol in biological fluids.

Spectrofluorimetric Determination of Atenolol and Carvedilol in Pharmaceutical Preparations after Optimization of Parameters using Response Surface Methodology

Background: The present work is aimed to study the effect of different parameters on the fluorescence intensity of atenolol (ATE) and carvedilol (CAR) and optimization by response surface methodology (RSM) to provide a simple analytical method for their quantification in pharmaceutical formulations. Methods: Various parameters affecting the fluorescence intensity, i.e., sodium dodecyl sulfate (SDS) concentration, pH, volume fraction of solvents were optimized using RSM. Then, the optimized parameters were applied to the validation of a method for fluorimetric determination of β-blockers in their pharmaceutical preparations. Results: It is obtained that under the optimum conditions for determination of ATE, the method provided a linear range between 130 to 750 ng/mL with a coefficient of correlation (r) of 0.9996. Also, the limit of detection and limit of quantification (LOD and LOQ) were 40 ng/mL and 130 ng/mL, respectively. Moreover, it is observed that, the linearity of method for determination of CAR was between 0.37 to 4.0 ng/mL and LOD and LOQ of method were 0.11 ng/mL and 0.37 ng/mL, respectively. Conclusion: An accurate, sensitive and reliable spectrofluorimetric method was developed anf successfully used to determine the (ATE) and carvedilol (CAR) in their pharmaceutical preparations.

Microbial detoxification of carvedilol, a β-adrenergic antagonist, by the filamentous fungus Cunninghamella echinulata

Beta adrenergic antagonists like carvedilol are typical environmental pollutants detected in wastewater and surface water. Human metabolism of carvedilol is well investigated, while its environmental fates are still unknown. In recent years, there have been appearing reports on high toxicity of β-blockers toward aquatic organisms. In this paper the ability of the filamentous fungus C. echinulata to eliminate the β-blocker has been described for the first time. An 83% loss of carvedilol was observed after 120 h incubation of the tested fungus with the compound, where hydroxylated carvedilol metabolites were identified as the major biotransformation products. Carvedilol degradation by C. echinulata was proceeded by hydroxylation and conjugation reactions similar to its mammalian metabolism. Glucose conjugate was found in the fungi cultures, whereas glucuronide conjugates were detected in mammals. The impact of carvedilol on the functionality of fungal cells was also evaluated. A 2-fold decrease in the PC/PE ratio was noticed in the C. echinulata cell membrane after the exposition to carvedilol compared to control mycelium incubated without the β-blocker. The change can denote perturbation of fungal cell membrane integration by carvedilol. Moreover, 2.8-fold lower toxicity of postcultures supernatants toward D. magna were shown in contrast to abiotic control.

Comparison of free-radical inhibiting antioxidant properties of carvedilol and its phenolic metabolites

Carvedilol is a widely prescribed drug for the treatment of heart failure and the prevention of associated ventricular arrhythmias. It has also been reported to function as a biological antioxidant via hydrogen atom transfer from its carbazole N-H moiety to chain-propagating radicals. Metabolites of the drug include phenolic derivatives, such as 3-hydroxy-, 4'-hydroxy- and 5'-hydroxycarvedilol, which are also potential antioxidants. A comparison of the radical-inhibiting activities of the parent drug and the three metabolites was carried out in two separate assays. In the first, hydrogen atom transfer from these four compounds to the stable radical DPPH was measured by the decrease in the UV-visible absorption at 515 nm of the latter. The known radical inhibitors BHT, 4-hydroxycarbazole and α-tocopherol were employed as benchmarks in parallel experiments. In the second assay, inhibition of the photoinduced free-radical 1,2-addition of Se-phenyl p-tolueneselenosulfonate to cyclopropylacetylene, along with competing ring-opening of the cyclopropane ring, was monitored by ¹H NMR spectroscopy in the presence of the carvedilol-based and benchmark antioxidants. In both assays, carvedilol displayed negligible antioxidant activity, while the three metabolites all proved superior radical inhibitors to BHT, with radical-quenching abilities in the order 3-hydroxy- > 5'-hydroxy > 4'-hydroxycarvedilol. Among the metabolites, 3-hydroxycarvedilol displayed even stronger activity in both assays than α-tocopherol, the best of the benchmark antioxidants. These results suggest that the radical-inhibiting antioxidant properties that have been attributed to carvedilol are largely or exclusively due to its metabolites and not to the parent drug itself.

Chiral analysis of carvedilol and its metabolites hydroxyphenyl carvedilol and O-desmethyl carvedilol in human plasma by liquid chromatography-tandem mass spectrometry: Application to a clinical pharmacokinetic study

Carvedilol is an antihypertensive drug, which is available in clinical practice as a racemic mixture. (S)-(-)-carvedilol is a β- and α1-adrenergic antagonist, while (R)-(+)-carvedilol only acts as an α1-adrenergic antagonist. Carvedilol is metabolized mainly by glucuronidation and, to a lesser extent, by CYP2D6 to hydroxyphenyl carvedilol (OHC) and by CYP2C9 to O-desmethyl carvedilol (DMC). This study describes the development and validation of a method for the sequential analysis of the enantiomers of carvedilol, OHC and DMC in plasma using a Chirobiotic(®) V chiral-phase column coupled to an LC-MS/MS system. The method was linear in the range of 0.05-100, 0.05-10 and 0.02-10 ng/mL for the carvedilol, OHC and DMC enantiomers, respectively. Application of the method to the investigation of a patient with type 2 diabetes mellitus treated with a single oral dose of 25mg racemic carvedilol showed plasma accumulation of the (R)-(+)-carvedilol, (R)-(+)-DMC and (R)-(+)-OHC enantiomers. These results suggest that plasma accumulation of (R)-(+)-carvedilol cannot be explained by its oxidative metabolism.

A dispersive liquid-liquid microextraction and chiral separation of carvedilol in human plasma using capillary electrophoresis

BACKGROUND

Development of simple, rapid and precise analysis of chiral drugs in biological samples is an important issue. Dispersive liquid-liquid microextraction in combination with CE using field amplified sample injection has been of interest because of its capability to analyze trace amount of drugs.

METHODS

Dispersive liquid-liquid microextraction-CE-field amplified sample injection was employed for chiral separation of carvedilol in human plasma using UV-DAD detector and the developed method has been validated according to US FDA method validation guideline for bioanalysis.

RESULTS

The method was linear over a concentration range of 12.5-100 ng/ml for each carvedilol enantiomer (R(2) = 0.998) and the mean recoveries ranged from 91 to 107%.

CONCLUSION

The method was adapted for sensitive, selective and rapid determination of carvedilol enantiomers in human plasma samples.

Clinical applications of fast liquid chromatography: a review on the analysis of cardiovascular drugs and their metabolites

One of the major challenges facing the medicine today is developing new therapies that enhance human health. To help address these challenges the utilization of analytical technologies and high-throughput automated platforms has been employed; in order to perform more experiments in a shorter time frame with increased data quality. In the last decade various analytical strategies have been established to enhance separation speed and efficiency in liquid chromatography applications. Liquid chromatography is an increasingly important tool for monitoring drugs and their metabolites. Furthermore, liquid chromatography has played an important role in pharmacokinetics and metabolism studies at these drug development stages since its introduction. This paper provides an overview of current trends in fast chromatography for the analysis of cardiovascular drugs and their metabolites in clinical applications. Current trends in fast liquid chromatographic separations involve monolith technologies, fused-core columns, high-temperature liquid chromatography (HTLC) and ultra-high performance liquid chromatography (UHPLC). The high specificity in combination with high sensitivity makes it an attractive complementary method to traditional methodology used for routine applications. The practical aspects of, recent developments in and the present status of fast chromatography for the analysis of biological fluids for therapeutic drug and metabolite monitoring, pharmacokinetic studies and bioequivalence studies are presented.