Pharmacokinetics of acetaminophen in Hong Kong Chinese subjects

Rapid identification of potential nonsteroidal anti-inflammatory drug overdose-induced liver toxicity and prediction of follow-up exposure: Integrating bioanalytical and population pharmacokinetic assay

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used drugs that can cause liver toxicity. The aim of this study was to integrate bioanalytical and population pharmacokinetic (PopPK) assay to rapidly screen and quantify the concentrations of NSAIDs in plasma and monitor clinical safety. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantification of acetaminophen (APAP), flurbiprofen (FLB), aspirin (ASP), and ibuprofen (IBP), four commonly used NSAIDs. The PopPK model of the signature toxicant was analyzed based on the published literature. The LC-MS/MS method was successfully validated and applied to determine NSAID concentrations in patient plasma samples. APAP, ASP, and IBP data were best fitted using a one-compartment model, and FLB data were best fitted using a two-compartment model. Bootstrapping and visual predictive checks suggested that a robust and reliable pharmacokinetic model was developed. A fast, simple, and sensitive LC-MS/MS method was developed and validated for determining APAP, FLB, ASP, and IBP in human plasma. Combined with the PopPK model, this method was applied to rapidly analyze the concentrations of NSAIDs in clinical samples from patients presenting to the emergency department with acute liver dysfunction and monitored NSAIDs clinical safety.

Spatial analysis of renal acetaminophen metabolism and its modulation by 4-methylpyrazole with DESI mass spectrometry imaging

Acute kidney injury (AKI) is a common complication in acetaminophen (APAP) overdose patients and can negatively impact prognosis. Unfortunately, N-acetylcysteine, which is the standard of care for the treatment of APAP hepatotoxicity does not prevent APAP-induced AKI. We have previously demonstrated the renal metabolism of APAP and identified fomepizole (4-methylpyrazole, 4MP) as a therapeutic option to prevent APAP-induced nephrotoxicity. However, the kidney has several functionally distinct regions, and the dose-dependent effects of APAP on renal response and regional specificity of APAP metabolism are unknown. These aspects were examined in this study using C57BL/6J mice treated with 300-1200 mg/kg APAP and mass spectrometry imaging (MSI) to provide spatial cues relevant to APAP metabolism and the effects of 4MP. We find that renal APAP metabolism and generation of the nonoxidative (APAP-GLUC and APAP-SULF) and oxidative metabolites (APAP-GSH, APAP-CYS, and APAP-NAC) were dose-dependently increased in the kidney. This was recapitulated on MSI which revealed that APAP overdose causes an accumulation of APAP and APAP GLUC in the inner medulla and APAP-CYS in the outer medulla of the kidney. APAP-GSH, APAP-NAC, and APAP-SULF were localized mainly to the outer medulla and the cortex where CYP2E1 expression was evident. Interestingly, APAP also induced a redistribution of reduced GSH, with an increase in oxidized GSH within the kidney cortex. 4MP ameliorated these region-specific variations in the formation of APAP metabolites in renal tissue sections. In conclusion, APAP metabolism has a distinct regional distribution within the kidney, the understanding of which provides insight into downstream mechanisms of APAP-induced nephrotoxicity.

Inter-ethnic differences in pharmacokinetics-is there more that unites than divides?

Inter-ethnic variability in pharmacokinetics (PK) has been attributed to several factors ranging from genetic to environmental. It is not clear how current teaching in higher education (HE) reflects what published literature suggests on this subject. This study aims to gain insights into current knowledge about inter-ethnic differences in PK based on reports from published literature and current teaching practices in HE. A systematic literature search was conducted on PubMed and Scopus to identify suitable literature to be reviewed. Insights into inter-ethnic differences in PK teaching among educators in HE and industry were determined using a questionnaire. Thirty-one percent of the studies reviewed reported inter-ethnic differences in PK, of these, 37% of authors suggested genetic polymorphism as possible explanation for the inter-ethnic differences observed. Other factors authors proposed included diet and weight differences between ethnicities. Most respondents (80%) who taught inter-ethnic difference in PK attributed inter-ethnic differences to genetic polymorphism. While genetic polymorphism is one source of variability in PK, the teaching of genetic polymorphism is better associated with interindividual variabilities rather than inter-ethnic differences in PK as there are no genes with PK implications specific to any one ethnic group. Nongenetic factors such as diet, weight, and environmental factors, should be highlighted as potential sources of interindividual variation in the PK of drugs.

A reliable LC-MS/MS method for the quantification of N-acetyl-p-benzoquinoneimine, acetaminophen glutathione and acetaminophen glucuronide in mouse plasma, liver and kidney: Method validation and application to a pharmacokinetic study

A rapid, specific, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated to simultaneously quantify N-acetyl-p-benzoquinoneimine (NAPQI), acetaminophen-glutathione (acetaminophen-glut) and acetaminophen-glucuronide (acetaminophen-gluc) in mouse plasma, liver and kidney homogenates. Analytes were eluted by a binary gradient mobile phase composed of water (phase A) and methanol containing 0.1% formic acid (phase B) at a flow rate of 0.3 mL/min, which was performed on a CAPCELL PAK C₁₈ MG II column. It took 3.2 min to detect three analytes in a single run. Quantification was carried out in positive mode combined with multiple reaction monitoring. The validation of the LC-MS/MS method consisted of specificity, linearity, precision, accuracy, protein precipitation recovery, matrix effect, dilution integrity and stability. The plasma and tissue homogenate calibration curves were linear over concentration ranges of 0.050-5.00, 0.050-5.00 and 0.100-40.0 μg/mL, with a lower limit of quantification of 0.050, 0.050, and 0.100 μg/mL for NAPQI, acetaminophen-glut and acetaminophen-gluc, respectively. The intra- and inter-run precision values were within 12.47% for NAPQI, 12.11% for acetaminophen-glut and 11.86% for acetaminophen-gluc at their lower limit of quantitation levels. The samples were stable under all tested conditions. This method was successfully applied to study the pharmacokinetics of NAPQI, acetaminophen-glut and acetaminophen-gluc in ICR mice following oral administration of 200 mg/kg of acetaminophen suspension.

Comparison of the analgesic effect of intravenous acetaminophen with that of flurbiprofen axetil on post-breast surgery pain: a randomized controlled trial

OBJECTIVE

Acetaminophen is known to be a relatively weak analgesic with fewer side effects than nonsteroidal anti-inflammatory drugs (NSAIDs). This study aimed to determine whether intravenous (iv) acetaminophen produces comparable analgesic effects to those of flurbiprofen (positive control drug), an intravenously injectable NSAID, after partial mastectomies. The primary outcome assessed was pain intensity during the first 24 h after the operation, and the secondary outcome was the satisfaction rating at discharge.

METHODS

After obtaining Institutional Ethics Committee approval, a series of 40 consecutive female patients who were scheduled for partial mastectomies were enrolled. Participants were randomly divided into two groups: an acetaminophen (1000 mg × 3) group (group A) and a flurbiprofen (50 mg × 3) group (group F). Each drug was administered 15 min before the end of surgery, and at 6 and 12 h after the operation. Postoperative pain was evaluated using a 100-mm visual analog scale (VAS) at 3, 6, and 24 h postoperatively. Satisfaction rating was evaluated on a 5-point scale (very good, good, well, bad, and very bad).

RESULTS

VAS scores (mm) with movement in groups A and F at 3, 6, and 24 h after the surgery were 22 vs. 28, 14 vs. 24, and 12 vs. 20.5 (median), respectively, with no significant differences between the two groups. Eighteen of 20 patients in group A and 20 of 20 patients in group F expressed a satisfaction rating of greater than good.

CONCLUSIONS

Acetaminophen produces an equivalent analgesic effect to flurbiprofen in post-partial mastectomy patients.

Interindividual variation in gene expression responses and metabolite formation in acetaminophen-exposed primary human hepatocytes

Acetaminophen (APAP) is a readily available over-the-counter drug and is one of the most commonly used analgesics/antipyretics worldwide. Large interindividual variation in susceptibility toward APAP-induced liver failure has been reported. However, the exact underlying factors causing this variability in susceptibility are still largely unknown. The aim of this study was to better understand this variability in response to APAP by evaluating interindividual differences in gene expression changes and APAP metabolite formation in primary human hepatocytes (PHH) from several donors (n = 5) exposed in vitro to a non-toxic to toxic APAP dose range. To evaluate interindividual variation, gene expression data/levels of metabolites were plotted against APAP dose/donor. The correlation in APAP dose response between donors was calculated by comparing data points from one donor to the data points of all other donors using a Pearson-based correlation analysis. From that, a correlation score/donor for each gene/metabolite was defined, representing the similarity of the omics response to APAP in PHH of a particular donor to all other donors. The top 1 % highest variable genes were selected for further evaluation using gene set overrepresentation analysis. The biological processes in which the genes with high interindividual variation in expression were involved include liver regeneration, inflammatory responses, mitochondrial stress responses, hepatocarcinogenesis, cell cycle, and drug efficacy. Additionally, the interindividual variation in the expression of these genes could be associated with the variability in expression levels of hydroxyl/methoxy-APAP and C8H13O5N-APAP-glucuronide. The before-mentioned metabolites or their derivatives have also been reported in blood of humans exposed to therapeutic APAP doses. Possibly these findings can contribute to elucidating the causative factors of interindividual susceptibility toward APAP.

Evaluation of peripheral blood microsampling techniques in combination with liquid chromatography-high resolution mass spectrometry for the determination of drug pharmacokinetics in clinical studies

New bioanalytical assays were developed, validated, and applied in a clinical study for quantitative measurement of acetaminophen concentrations in blood and plasma samples. Furthermore, after validation, the bioanalytical assays were used for determination of pharmacokinetics within a group of six healthy male human volunteers after admission of a single oral dose of 500 mg of acetaminophen. Quantitative analyses were done by means of liquid chromatography-high resolution mass spectrometry and blood samples were collected at various sampling time points using different peripheral blood microsampling techniques. Post-dose peripheral collected blood samples were applied for the preparation of dry blood spots, dried matrix on paper discs, and peripheral plasma. Pharmacokinetic parameters determined were clearance (Cl), area under the curve (AUC), volume of distribution (Vd ), peak concentration (Cmax ), time of occurrence of peak concentration (Tmax ) and half-life time (T½ ). Observed pharmacokinetic values were not statistically (ANOVA) different compared to in literature reported values based on venous blood collection. The present pilot study demonstrated the feasibility of peripheral blood microsampling techniques in combination with quantitative liquid chromatography-high resolution mass spectrometry analysis for the determination of pharmacokinetics in clinical studies.

Simultaneous LC-MS/MS quantitation of acetaminophen and its glucuronide and sulfate metabolites in human dried blood spot samples collected by subjects in a pilot clinical study

BACKGROUND

In support of a pilot clinical trial using acetaminophen as the model compound to assess dried blood spot (DBS) sampling as the method for clinical pharmacokinetic sample collection, a novel sensitive LC-MS/MS method was developed and validated for the simultaneous determination of acetaminophen and its major metabolites, acetaminophen glucuronide and sulfate, in human DBS samples collected by subjects via fingerprick.

RESULTS

The validated assay dynamic range was from 50.0 to 5000 ng/ml for each compound using a 1/8´´ (3-mm) disc punched from a DBS sample. Baseline separation of the three analytes was achieved to eliminate the possible impact of insource fragmentation of the conjugated metabolites on the analysis of the parent. The overall extraction efficiency was from 61.3 to 78.8% for the three analytes by direct extraction using methanol.

CONCLUSION

The validated method was successfully implemented in the pilot clinical study with the obtained pharmacokinetic parameters in agreement with the values reported in literature.

Investigating paracetamol pharmacokinetics using venous and capillary blood and saliva sampling

Objective

The aim of this study was to develop, validate and apply a high performance liquid chromatography (HPLC) assay for analysis of paracetamol, paracetamol glucuronide and paracetamol sulfate in plasma (venous and capillary) and saliva to study paracetamol pharmacokinetics in healthy volunteers.

Methods

Samples were prepared using protein precipitation and analysed using reverse phase HPLC with UV detection. This assay was applied to venous and capillary plasma and saliva samples from 20 healthy volunteers after paracetamol 1 g four times daily for three days.

Key findings

The HPLC assay for paracetamol and its metabolites was found to be sensitive and selective in plasma and saliva samples over the range 0.05–50 mg/l with an inter- and intraday precision and accuracy within 11.2% and 11.1%, respectively. Mean recoveries for all analytes were > 88%. A study of paracetamol pharmacokinetics in healthy volunteers found close agreement between the sampling matrices for paracetamol and metabolites (metabolites were not detected in saliva). The value for area under the concentration–time curve over the 6 h dosing interval of venous plasma (45.3 ± 12.9 mg/l.h) was significantly higher than that observed for capillary plasma (33.8 ± 12.9 mg/l.h) or saliva (35.1 ± 9.4 mg/l.h; P > 0.01).

Conclusions

Capillary blood and saliva collection were found to be reliable sampling matrices for the evaluation of paracetamol pharmacokinetics, although paracetamol metabolites were not detected in saliva.

Effects of imatinib mesylate on the pharmacokinetics of paracetamol (acetaminophen) in Korean patients with chronic myelogenous leukaemia

AIMS

The major objective of the present study was to investigate the effect of imatinib on the pharmacokinetics of paracetamol in patients with chronic myelogenous leukaemia (CML).

METHODS

Patients (n = 12) received a single oral dose of acetaminophen 1000 mg on day 1 (control). On days 2-8, imatinib 400 mg was administered daily. On day 8 (treatment), another 1000 mg dose of paracetamol was administered 1 h after the morning dose of imatinib 400 mg. Blood and urine samples were collected for bioanalytical analyses.

RESULTS

The area under the plasma concentration-time curve (AUC) for paracetamol, paracetamol glucuronide and paracetamol sulphate under control conditions was similar to that after treatment with imatinib; the 90% confidence interval of the log AUC ratio was within 0.8 to 1.25. Urinary excretion of paracetamol, paracetamol glucuronide and paracetamol sulphate was also unaffected by imatinib. The pharmacokinetics of paracetamol and imatinib in Korean patients with CML were similar to previous pharmacokinetic results in white patients with CML. Co-administration of a single dose of paracetamol and multiple doses of imatinib was well tolerated and safety profiles were similar to those of either drug alone.

CONCLUSIONS

The pharmacokinetics of paracetamol and its major metabolites in the presence of imatinib were similar to those of the control conditions and the combination was well tolerated. These findings suggest that imatinib can be safely administered with paracetamol without dose adjustment of either drug.

Paracetamol metabolism and related genetic differences

Paracetamol (acetaminophen) is a worldwide used analgesic and antipyretic drug. It is metabolised via several metabolic pathways, including glucuronidation, sulfation, oxidation, hydroxylation, and deacetylation: Hepatic and other organ damage may occur, especially in overdose, because of the accumulation of a toxic metabolite. Intersubject and ethnic differences have been reported in paracetamol metabolism activation, suggesting possible differences in susceptibility to toxicity and in pain alleviation, linked to different pharmacogenetic profiles. This article aims at reviewing, in the literature, the links between paracetamol metabolism and enzyme genotypes in the context of toxic side effects and efficacy of paracetamol in therapeutics.

Simultaneous determination of paracetamol and dextropropoxyphene in human plasma by liquid chromatography/tandem mass spectrometry: application to clinical bioequivalence studies

A liquid chromatography/mass spectrometry method for simultaneous determination of paracetamol and dextropropoxyphene in human plasma is described. Paracetamol and dextropropoxyphene, together with their internal standards (tolbutamide and pyrroliphene), were extracted from 0.5 mL of plasma using solid-phase extraction. The chromatography was performed using a Thermo Hypersil APS-2 Amino column (250 mm x 4.6 mm, 5 microm) with a mobile phase consisting of acetonitrile and 0.4% glacial acetic acid in water (20:80). The total run time was 6 min for each sample. The triple-quadrupole mass spectrometer was operated in both positive (for detection of dextropropoxyphene and its IS pyrroliphene) and negative (for detection of paracetamol and its IS tolbutamide) modes using a polarity-switching technique. Multiple reaction monitoring was used for quantification. The method was linear over the concentration range of 0.1-20 microg/mL for paracetamol and 0.5-80 ng/mL for dextropropoxyphene. The intra- and inter-day precision were less than 10%, and the accuracy ranged from 92.2-110.9%. The lower limits of quantification were 0.1 microg/mL for paracetamol and 0.5 ng/mL for dextropropoxyphene. The present method provides a robust, fast and sensitive analytical tool for both paracetamol and dextropropoxyphene, and has been successfully applied to a clinical bioequivalence study in 14 subjects.