Urinary Excretion Profiles Research Articles

Safety, pharmacokinetics, and food-effect of pivmecillinam after single- and multiple-dose in healthy Chinese subjects: a phase I study.

Urinary tract infection (UTI) is one of the most prevalent bacterial infectious diseases worldwide. However, the resistance of urinary pathogens to other UTI antibiotics such as trimethoprim and trimethoprim/sulphamethoxazole increased. Pivmecillinam is a prodrug of mecillinam, which is effective for the treatment of urinary tract infections. The purpose of this study was to assess the safety, and pharmacokinetics of pivmecillinam and mecillinam after single- and multiple-dose oral administration of pivmecillinam tablets in healthy Chinese subjects. The study also investigated the profile of urinary excretion of mecillinam, as well as the effect of food and gender on the pharmacokinetics of pivmecillinam and mecillinam. This study was a single-center, open-label phase I study carried out in three groups. In total, 34 subjects were included in the study: group 1-food effect study with pivmecillinam 200mg (n = 12); group 2-single- and multiple-dose study with pivmecillinam 400mg (n = 12); group 3-single dose study with pivmecillinam 600mg (n = 10). The plasma and urine concentrations of pivmecillinam and mecillinam were measured, and their pharmacokinetics were calculated. Treatment-emergent adverse events were evaluated and recorded in safety assessments for three groups. No severe adverse events were found in this study. After a single dose of pivmecillinam was taken orally, the maximum plasma concentration (Cmax) and the area under the concentration-time curve (AUC) of pivmecillinam increased in a dose-proportional manner, nor did mecillinam. Food had significant effects on Cmax and AUC0-t of pivmecillinam and Cmax of mecillinam. The mean cumulative percentage of urine excretion of mecillinam at 0 to 24h ranged from 35.5 to 44.0%. Urinary cumulative excretion is relative to the drug dose, but the diet and multiple-dose administration did not affect the urinary cumulative excretion rate. The safety and pharmacokinetics of pivmecillinam and mecillinam after single- (200/400/600mg) or multiple-dose (400mg) administration were demonstrated in healthy Chinese subjects. Food affected the pharmacokinetics of pivmecillinam and mecillinam.

Chronic consumption of orange juice modifies urinary excretion of flavanone gut-derived metabolites through gut microbiota modulation

The metabolism and absorption of citrus flavanones are intrinsically linked to the gut microbiota, creating a bidirectional relationship where these compounds influence the microbiome, and in turn, the microbiota affects their metabolism. This study evaluates the effect of acute and chronic consumption of orange juice (OJ) on the urinary excretion of gut-derived flavanone metabolites and the gut microbiota. Health volunteers ingested 500 mL of OJ for 60 days in a single-arm human intervention study. Blood and feces were collected at baseline and after 60 days, with an additional 24-hour urine collection after a single dose on day 1 and day 63. LC-MS/MS analyzed urinary flavanone metabolites, while 16S rRNA sequencing characterized gut microbiota. Total urinary hesperetin conjugates excretion significantly decreased over 60 days, while gut-derived total phenolic acids, particularly three hydroxybenzoic acids, increased. Moreover, the heterogeneity of the total amount of flavanone conjugates, initially categorizing individuals into high-, medium- and low- urinary excretor profiles, shifted towards medium-excretor, except for five individuals who remained as low-excretors. This alteration was accompanied by a decrease in intestinal β-glucosidase activity and a shift in the relative abundance of specific genera, such as decreases in Blautia, Eubacterium hallii, Anaerostipes, and Fusicatenibacter, among which, Blautia was associated with higher urinary flavanone conjugates excretion. Conversely, an increase in Prevotella was observed. In summary, chronic OJ consumption induced transient changes in gut microbiota and altered the metabolism of citrus flavanones, leading to distinct urinary excretion profiles of flavanone metabolites.

Urinary excretion profile of higenamine in females after oral administration of supplements – Doping scenario

In 2017, higenamine was added to the World Antidoping Agency’s (WADA) Prohibited list under group S3: beta-2 agonists and it is banned for athletes both in – and out of competition. Aim of this study was to characterize the urinary excretion profile of higenamine and its metabolite coclaurine after oral administration of multiple doses of higenamine capsules. For this purpose, an administration study including female basketball players was performed.For the detection of higenamine and cocalurine in the collected urine samples, a new, fast, and highly sensitive quantitative on-line SPE LC HRMS method was developed and validated. The method was applied for the quantification of higenamine and cocalurine in urine and their excretion pattern was defined. Results obtained show substantial inter-individual differences in the excretion profile of higenamine and coclaurine. For higenamine, half-lives were estimated to be between 4 and 27 h, and for coclaurine between 5 and 25 h. Furthermore, the data indicate that the elimination of coclaurine is rate-limited by its formation. Higenamine could be detected at a urine concentration above 10 ng/mL for at least 20 h after the last application for all study participants.

Quantitative analysis of primaquine and its metabolites in human urine using liquid chromatography coupled with tandem mass spectrometry

Primaquine (PQ), a prototype 8-aminoquinoline (8-AQ) drug used to treat malaria, is rapidly metabolized into different inactive and active metabolites. Due to the hemolytic toxicity, the uses of PQ have been confined. To understand its overall metabolism and its relation to drug efficacy and toxicity, profiling of urine for the parent drug and its metabolites is important. The current study presents a convenient and rapid method for simultaneously quantifying primaquine (PQ) and its metabolites in human urine. A simple liquid–liquid extraction followed by chromatographic separation and quantification through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed and validated to quantify PQ and its eleven metabolites in the urine of healthy human volunteers who received a single oral dose of PQ. The developed method separated fourteen analytes, including internal standards, within nine minutes of run time. The linearity of all analytes was suitable in the range of 1–500 ng/mL. The extraction recovery for all concentrations of analytes from urine was ranged from 90.1 to 112.9 %. The relative standard deviation for intra- and inter-day precision were < 9.8 and < 10.7 %, respectively. Along with PQ, its different metabolites were detected in urine. Primaquine-5,6-orthoquinone, the N-carbamoylglucuronide conjugate of PQ and carboxyprimaquine were the major metabolites found in urine. Significant enantiomeric differences in the urinary excretion profiles for PQ and metabolites were observed. This analytical method can be implemented in the pharmacokinetic analysis of PQ to explain its toxicity and clinical decision making.

1-methylhistamine as a potential biomarker of food histamine intolerance. A pilot study.

Efforts are currently being directed to identify a non-invasive marker that can serve as a solid and clinically irrefutable diagnostic criterion for histamine intolerance associated with diamine oxidase (DAO) deficiency. Accordingly, the identification of biomarkers of histamine (HA) metabolism in urine is proposed as a possible new diagnostic strategy. It is hypothesized that individuals with histamine intolerance could have a different urinary profile of HA and its metabolites in comparison with the healthy population. Thus, the aim of this study was to assess the urinary excretion of HA and 1-methylhistamine (MHA) in individuals diagnosed with histamine intolerance and in a control group. Levels of HA and MHA were compared between 24 h and first morning spot urine in a subgroup of 14 control individuals. Then, HA and MHA concentrations in spot urine of 32 histamine intolerant and 55 control individuals were determined by ultra-high performance liquid chromatography and fluorometric detection (UHPLC-FL) and normalized by creatinine. No differences were found between HA and MHA levels in 24 h and first morning samples. Overall, histamine intolerant patients presented a distinct urinary excretion profile compared to the control group due to lower levels of MHA. No differences in urinary MHA were observed related to serum DAO activity. Spot urine samples were thus validated as a reliable tool to determine the urinary excretion of HA and MHA. These results constitute a starting point for the study of HA metabolomics as a suitable and non-invasive approach to histamine intolerance diagnosis.

Urinary excretion profile of prednisolone and prednisone after rectal administration: Significance in antidoping analysis.

The rectal administration of glucocorticoids, as well as any injectable, and oral ones, is currently prohibited by the World Anti-Doping Agency when occurs "in competition." A reporting level of 100 ng/ml for prednisolone and 300 ng/ml for prednisone was established to discriminate the allowed and the prohibited administration. Here, the urinary excretion profiles of prednisone and prednisolone were evaluated in five volunteers in therapy with glucocorticoid-based rectal formulations containing prednisone or prednisolone caproate. The urinary levels of the excreted target compounds were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following the procedure validated and currently in use in our laboratory to detect and quantitate glucocorticoids in urine. Predictably, the excretion trend of the analytes of interest were generally comparable with those obtained after oral administration, even if the excretion profile showed a broad interindividual variability, with the absorption rate and the systemic bioavailability after rectal administration being strongly influenced by the type of formulations (suppository or rectal cream, in our case) as well as the physiological conditions of the absorption area. Results showed that the target compounds were detectable for at least 30 h after drug administration. After suppository administration, prednisolone levels reached the maximum after 3h from drug administration and then dropped below the reporting level after 15-21 h; prednisone reached the maximum after 3h from drug administration, and then dropped below the reporting level after 12-15 h. After cream administration, both prednisone and prednisolone levels remained in a concentration below the reporting level throughout the entire monitored period.

Urinary Excretion Profile of Cannabinoid Analytes Following Acute Administration of Oral and Vaporized Cannabis in Infrequent Cannabis Users.

Traditionally, smoking has been the predominant method for administering cannabis, but alternative routes of administration have become more prevalent. Additionally, research examining urinary cannabinoid excretion profiles has primarily focused on 11-nor-9-carboxy-∆9-tetrahydrocannabinol (∆9-THC-COOH), a metabolite of ∆9-tetrahydrocannabinol (∆9-THC), as the primary analyte. The aim of the current study was to characterize the urinary excretion profile of ∆9-THC-COOH, ∆9-THC, ∆8-tetrahydrocannabinol (∆8-THC), 11-hydroxy-∆9-tetrahydrocannabinol (11-OH-∆9-THC), ∆9-tetrahydrocannabivarin (THCV), 11-nor-∆9-tetrahydrocannabivarin-9-carboxlic acid (THCV-COOH), cannabidiol (CBD), cannabinol (CBN) and 8,11-dihydroxytetrahydrocannabinol (8,11-diOH-∆9-THC) following controlled administration of both oral and vaporized cannabis. Participants (n = 21, 11 men/10 women) who were infrequent cannabis users ingested cannabis-containing brownies (0, 10 and 25 mg ∆9-THC) and inhaled vaporized cannabis (0, 5 and 20 mg ∆9-THC) across six double-blind outpatient sessions. Urinary concentrations of ∆9-THC analytes were measured at baseline and for 8 h after cannabis administration. Sensitivity, specificity and agreement between the three immunoassays (IAs) for ∆9-THC-COOH (cutoffs of 20, 50 and 100 ng/mL) and liquid chromatography-tandem mass spectrometry (LC-MS-MS) analyses (confirmatory cutoff concentrations of 15 ng/mL) were assessed. Urinary concentrations for ∆9-THC-COOH, ∆9-THC, 11-OH-∆9-THC, THCV, CBN and 8,11-diOH-∆9-THC all peaked at 5-6 h and 4 h following oral and vaporized cannabis administration, respectively. At each active dose, median maximum concentrations (Cmax) for detected analytes were quantitatively higher after oral cannabis administration compared to vaporized. Using current recommended federal workplace drug-testing criteria (screening via IA with a cutoff of ≥50 ng/mL and confirmation via LC-MS-MS at a cutoff of ≥15 ng/mL), urine specimens tested positive for ∆9-THC-COOH in 97.6% of oral sessions and 59.5% of vaporized sessions with active ∆9-THC doses. These data indicate that while ∆9-THC-COOH may serve as the most consistent confirmatory analyte under the current drug-testing guidelines, future work examining 11-OH-∆9-THC under similar parameters could yield an alternative analyte that may be helpful in distinguishing between licit and illicit cannabis products.

Diet and food type affect urinary pesticide residue excretion profiles in healthy individuals: results of a randomized controlled dietary intervention trial

Observational studies have linked pesticide exposure to various diseases, whereas organic food consumption has been associated with positive health outcomes. Organic farming standards prohibit the use of most pesticides, and organic food consumption may therefore reduce pesticide exposure. To determine the effects of diet (Western compared with Mediterranean) and food type (conventional compared with organic) and sex on urinary pesticide residue excretion (UPRE), as well as associations between specific diet components and UPRE. In this 2-wk, randomized dietary intervention trial, healthy adults were randomly allocated to an intervention (n=13) or conventional (n=14) group. Whereas participants in the intervention group consumed a Mediterranean diet (MedDiet) made entirely from organic foods, the conventional group consumed a MedDiet made entirely from conventional foods. Both groups consumed habitual Western diets made from conventional foods before and after the 2-wk intervention period. The primary outcome was UPRE. In addition, we assessed diet composition and pesticide residue profiles in foods eaten. Participants were aware of group assignment, but the study assessors were not. During the intervention period, total UPRE was 91% lower with organic (mean 17μg/d; 95% CI: 15, 19) than with conventional (mean 180μg/d; 95% CI: 153, 208) food consumption (P<0.0001). In the conventional group, switching from the habitual Western diet to the MedDiet increased insecticide excretion from 7 to 25μg/d (P<0.0001), organophosphate excretion from 5 to 19μg/d (P<0.0001), and pyrethroid residue excretion from 2.0 to 4.5μg/d (P<0.0001). Small but significant effects of sex were detected for chlormequat, herbicide, and total pesticide residue excretion. Changing from a habitual Western diet to a MedDiet was associated with increased insecticide, organophosphate, and pyrethroid exposure, whereas organic food consumption reduced exposure to all groups of synthetic chemical pesticides. This may explain the positive health outcomes linked to organic food consumption in observational studies. This trial was registered at www.clinicaltrials.gov as NCT03254537.

Математический анализ индивидуальных профилей биомаркеров повреждения почек у детей с пузырно-мочеточниковым рефлюксом

Objective. To assess the severity of lesions to renal parenchyma in children with grade II–IV vesicoureteral reflux (VUR) using hierarchical clustering based on the analysis of individual profiles of urinary biomarkers. Patients and methods. In this study, we evaluated the excretion of urinary biomarkers of inflammation (IL-8, IL-18, MCP-1), angiogenesis (VEGF), and fibrogenesis (TGF-β1) and compared them with clinical and demographic parameters of 65 patients with grade II–IV VUR aged 1 to 17 years (mean age 4.9 ± 3.1 years) with a normal glomerular filtration rate (GFR). The control group comprised healthy children without kidney diseases (n = 25). We used hierarchical clustering (construction of dendrogram using the Ward's method) for all biomarkers. Results. All patients, regardless of their age, gender, and VUR severity demonstrated a pathological profile of urinary biomarkers excretion, including IL-8, IL-18, MCP-1, VEGF, TGF-β1 (p &gt; 0.05). Using cluster analysis, we divided all patients into three subgroups (clusters) depending on the similarity of their individual biomarker profiles. We identified three main patterns of biomarkers that were associated with different severity of tubulointerstitial nephritis (TIN). The first pattern (I) with low levels of excretion of all biomarkers (p &lt; 0.001) correlated with mild TIN and was observed in 61.5% of children. The second pattern (II) with average excretion of IL-8, IL-18, MCP-1, TGF-β1 (p &lt; 0.01) and high VEGF excretion (p &lt; 0.001) was associated with moderate TIN and was observed in 32.2% of patients. The third pattern (III) with elevated excretion of IL-8, IL-18, MCP-1 and VEGF (by 2.5–17 times compared to patterns I and II) (p &lt; 0.01) correlated with severe TIN and was found in 6.1% of patients. Patients with the same VUR grades demonstrated different biomarker patterns. Conclusion. Hierarchical clustering enables comparison of individual profiles of urinary biomarkers with identified patterns, as well as their stratification into groups according to tubulointerstitial nephritis severity, which often remains undiagnosed with visualization techniques alone. Key words: children, cluster analysis, urinary biomarkers, vesicoureteral reflux, reflux nephropathy, tubulointerstitial nephritis

Biopsy or Biomarker? Children With Minimal Change Disease Have a Distinct Profile of Urinary Epidermal Growth Factor.

Background: In this study, the profile of urinary EGF excretion (uEGF/uCreat) was mapped in children presenting with prolonged proteinuria or with nephrotic syndrome refractory to or dependent of steroids. We investigated whether uEGF/uCreat could be linked to the underlying biopsy result, taking into account its response to immunosuppressive medication and to ACE inhibition, as well as genetic predisposition.Methods: Ninety-eight pediatric patients with initial presentation of nephrotic syndrome or prolonged proteinuria were included in this study, along with 49 healthy controls and 20 pediatric Alport patients. All patients had a normal kidney function and were normotensive during the course of the study, whether or not under ACE inhibition. In repeated urine samples, uEGF was measured and concentration was normalized by urine creatinine. In order to compare diagnosis on kidney biopsy, genetic predisposition and response of uEGF/uCreat to immunosuppression and to ACE inhibition, uEGF/uCreat is studied in a linear mixed effects model.Results: Patients with Minimal Change Disease (MCD) showed a significantly different profile of uEGF/uCreat in comparison to healthy children, as well as compared to patients with Focal Segmental Glomerulosclerosis (FSGS) or another glomerulopathy on kidney biopsy. The response of uEGF/uCreat to ACE inhibition was absent in minimal change disease and contrasted with an impressive beneficial effect of ACE inhibition on uEGF/uCreat in FSGS and other proteinuric glomerulopathies. Absence of a genetic predisposition was also associated with a significantly lower uEGF/uCreat.Conclusions: Despite preserved kidney function, children with a proteinuric or nephrotic glomerular disease on kidney biopsy show a significantly lower uEGF/uCreat, indicative of early tubulo-interstitial damage, which appears reversible under ACE inhibition in any underlying glomerulopathy except in minimal change disease. In view of the distinct profile of uEGF/uCreat in minimal change disease compared to other glomerulopathies, and the link between genetic predisposition and uEGF/uCreat, our study suggests that uEGF/uCreat can be a helpful tool to decide on the need for a renal biopsy in order to differentiate minimal change disease from other proteinuric glomerular diseases.

Urinary excretion and effects on visual placing response in mice of gamma-valero-lactone, an alternative to gamma‑hydroxy-butyrate for drug-facilitated sexual assault

Γ-Valero-lactone (GVL) is a freely marketed organic solvent and food additive. GVL is also an underrated legal substitute for γ-hydroxybutyric acid (GHB), and it is sold under the trade name "Tranquili-G". GVL is usually not included in forensic drug testing, even though it has been reported in drug-facilitated sexual assaults (DFSA).To date, few studies verified the effectiveness of GVL as a hypnotic/narcotic substance, and no data are available on its urinary excretion profile. This work aims to fill this knowledge gap and lead to the introduction of GVL in forensic drug testing, especially when DFSA is suspected.To monitor the timeframe of GVL activity in vivo, we have assessed the effects on sensorimotor responses in visual placing tests carried out on CD-1 mice at a dose of 400 mg/kg of GVL, administered by gastric gavage. In parallel, samples of the in vitro and in vivo metabolism studies were analyzed using a rapid and cost-effective analytical procedure based on gas chromatography coupled to mass spectrometry. Our data confirmed that GVL impairs visual placing response in mice in the first 4 h after the intake, and they also show that GVL is a less potent substitute of GHB. The urinary excretion profile of GVL is consistent with the results of the behavioral study, with a maximum of excretion in the first 5 h after the intake. GVL is only detectable in the first 0–8 h after the intake. Our data confirmed the same rapid urinary excretion rate of GHB in urine and the related forensic implications, with the risk of possible false-negative results, especially when DFSA is suspected.

Steroid Metabolism in Children and Adolescents With Obesity and Insulin Resistance: Altered SRD5A and 20α/20βHSD Activity.

Alterations in glucocorticoid metabolism may contribute to the development of obesity and insulin resistance (IR). Obesity in turn affects the androgen balance. The peripheral metabolism of steroids is equally an important determinant of their bioavailability and activity. The aim of this study was to evaluate steroid metabolism in obese children and to define which enzyme alterations are associated with IR. Clinical characteristics and anthropometric measurements were determined in 122 obese children and adolescents (72 girls, 50 boys) aged 8 – 18 years. 26 of them (21.3%) were diagnosed with IR (13 boys, 13 girls). Routine laboratory tests were performed and 24h urinary steroid excretion profiles were analyzed by gas chromatography/mass spectrometry. Positive relationship between 5α-reductase (SRD5A) activity and IR was found. According to the androsterone to etiocholanolone (An/Et) ratio the activity of SRD5A was significantly increased in obese children with IR, but the difference remained insignificant once the 5α-dihydrotestosterone to testosterone (5αDHT/T) ratio was considered. Furthermore, this relationship persisted in boys but was not observed in girls. The activity of 20α-hydroxysteroid dehydrogenase (20αHSD) and 20β-hydroxysteroid dehydrogenase (20βHSD) was reduced only in obese girls with IR. Conclude, in the context of obese children and adolescents with IR, we surmise that increased SRD5A represents a compensatory mechanism to reduce local glucocorticoid availability. This phenomenon is probably different in the liver (restriction) and in the adipose tissue (expected increase in activity). We show significant changes in 20αHSD and 20βHSD activity in obese girls with IR, but it is difficult to clearly determine whether the activity of these enzymes is an indicator of the function in their ovaries or adrenal glands.

Urine N-acetyl-Ser-Asp-Lys-Pro measurement as a versatile biomarker to assess adherence to angiotensin-converting enzyme inhibitors.

Poor adherence to treatment is a major health issue in hypertension. The large number of drugs to be detected limits the implementation of chemical adherence testing by liquid chromatography/mass spectrometry (LC-MS/MS). AcSDKP, a peptide accumulating in the presence of angiotensin-converting-enzyme inhibitor (ACEI) treatment, has been validated as a proven marker of adherence by enzyme-linked immunosorbent assay. Our aim was to validate urine measurements of AcSDKP compared with active metabolites of various ACEI, measured simultaneously by LC-MS/MS. We first studied the time-dependent relationships between urinary perindoprilat and AcSDKP in a pharmacokinetic/pharmacodynamic study in healthy volunteers. We then compared the sensitivity and specificity of urinary AcSDKP vs. three ACEI active metabolites (enalaprilat, perindoprilat, ramiprilat) taken as reference to detect nonadherence in spot urine samples from a prospective cohort of hypertensive outpatients. The urinary excretion profiles of AcSDKP and perindoprilat were similar, exhibited a significant correlation, and showed excellent agreement in healthy volunteers. In patients, we found a similar agreement between AcSDKP and the three ACEI metabolites urinary concentrations. The sensitivity and specificity for adherence assessment of urine AcSDKP was 92.2 and 100%, respectively. We observed a difference in the evaluation of good adherence between ACEI metabolites (85.7%) and AcSDKP (79.0%) because of discrepancies in samples where AcSDKP reached undetectability quicker than ACEI metabolites. This characteristic of AcSDKP is of particular interest and could better reflect the true adherence status of patients. Overall, spot urine AcSDKP measurement by LC-MS/MS is a reliable marker of the intake of ACEI treatment and could substitute ACEI metabolites detection.

SporTRIA study—a multicentre trial protocol for excretion kinetics of triamcinolone acetonide following sport-related intra-articular injections in knees: definitions of the washout periods

IntroductionIntra-articular (IA) and peri-articular glucocorticoid (GC) injections are common in sports medicine. However, from 1 January 2022, all injectable GC routes (including IA administration) will be prohibited in-competition by World...

Urinary excretion profiles of etizolam and its main metabolites after a single oral dose

Urinary excretion profiles of etizolam and its main metabolites after a single oral dose

Urinary excretion profile of methiopropamine in mice following intraperitoneal administration: A liquid chromatography-tandem mass spectrometry investigation.

We have considered the urinary excretion profile of methiopropamine (MPA), a thiophene ring-based structural analog of methamphetamine with similar stimulant effects, with the aim of selecting the most appropriate marker(s) of intake that may be useful in forensic analysis. For this purpose, in vitro studies were preliminarily performed on human liver microsomes for tracing the phase I metabolic pathways of MPA, preselecting the best candidates as potential target analytes, and designing the optimal experimental strategy. In vivo studies were then conducted on mice, after the intraperitoneal administration of a 10-mg/kg dose. Urine samples were collected every 3 h in the first 9 h and, subsequently, from 24 to 36 h, and stored at -80°C until further analysis. The measurements were performed using a targeted procedure based on liquid/liquid extraction followed by liquid chromatography-tandem mass spectrometry analysis. Our results show that in the time interval 0-9 h after administration, MPA was extensively oxidized mainly to nor-MPA, oxo-MPA, and two hydroxylated metabolites (ie, hydroxy-aryl-methiopropamine and hydroxy-alkyl-methiopropamine). All phase I metabolites underwent phase II metabolism, with the formation of nor-hydroxy-methiopropamine only in phase II, confirmed by the results obtained after enzymatic hydrolysis with β-glucuronidase and arylsulfatase. In the time interval 24-36 h after administration, only unchanged MPA and nor-MPA were detected, suggesting that these two markers are those endowed with the highest diagnostic value. The method was validated for these two principal markers, proving to be fit for anti-doping, toxicological, and forensic analyses.

Development and validation of a specific and sensitive liquid chromatography tandem mass spectrometry method for determination of tetrodotoxin in human urine and its pharmacokinetic study.

Tetrodotoxin (TTX) exhibits the therapeutic potential in blocking pain and in low doses can safely relieve severe pain. The urinary excretion profiles of TTX in humans have not been reported due to the extremely low lethal dose. In this study, a rapid and specific method based on protein precipitation coupled to liquid chromatography tandem mass spectrometry was developed to determine the level of TTX in human urine samples. 11-Deoxytetrodotoxin was used as an internal standard (IS). Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 320.0 → 162.1 for TTX and m/z 304.0 → 176.0 for 11-deoxyTTX. The separation of analytes was achieved on a hydrophilic interaction liquid chromatography column (250 × 4.6 mm, 5.0 μm). The mobile phase consisted of 5 mM ammonium formate in water (pH = 4.50) and 5 mM ammonium formate in acetonitrile (pH = 4.50). The flow rate was set at 0.80 mL/min in a gradient condition. Calibration plots were linear throughout the range 0.986-98.6 ng/mL of TTX in human urine. The intra-assay accuracies and precisions were within the acceptable range. The method was successfully applied to a urinary excretion study after intravenous administration of TTX to healthy volunteers. The developed method will be helpful for future pharmacological studies of TTX.

Using hydrocarbons as reagents

The compounds cis-6-(2-acetylvinylthio)purine (cis-AVTP) and trans-6-(2-acetylvinylthio)guanine (trans-AVTG) are glutathione-activated prodrugs of 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), respectively, that have comparable or lower IC50 values in tumor cells than 6-MP and 6-TG. Previously, we showed that cis-AVTP- and trans-AVTG-treated mice exhibited less bone marrow and intestinal toxicity and excreted a lower fraction of the administered dose in urine than did mice treated with equivalent 6-TG doses. To explain these results, the tissue distribution and levels of metabolites of cis-AVTP, trans-AVTG, and 6-TG were examined at 15, 30, and 45 min after i.p. treatment of mice with equimolar doses of these compounds. After prodrug treatment, the thiopurines, the corresponding thiopurine ribosides and nucleotides, thioxanthine (TX), and thiouric acid (TU) were quantitated in plasma, red blood cells, liver, and intestine. Thiopurine and thiopurine riboside and nucleotide area under the curve between 15 and 45 min [AUC(15–45)] values were generally comparable after cis-AVTP and trans-AVTG treatments but were lower than those after 6-TG treatment. A higher liver/plasma metabolite ratio was evident after trans-AVTG treatment than after cis-AVTP or 6-TG treatments, which exhibited similar liver/plasma ratios. Treatment with cis-AVTP yielded the highest AUC(15–45) for TX and TU in plasma, liver, and intestine. Prodrug treatment did not change the concentration of reduced or oxidized glutathione in tissue homogenates. Collectively, these results show distinct patterns of metabolites depending upon the compound used and suggest that differences in metabolite levels and composition after cis-AVTP, trans-AVTG, and 6-TG treatments may partially explain the different toxicity and urinary metabolite excretion profiles previously observed among cis-AVTP, trans-AVTG, and 6-TG.

Diffusion modelling of percutaneous absorption kinetics. Predicting urinary excretion from in vitro skin permeation tests (IVPT) for an infinite dose

In this work, we developed a number of generalised skin diffusion based pharmacokinetic models to relate published in vivo urinary excretion data to matching experimentally generated in vitro human skin permeation test (IVPT) data for a series of topically applied salicylate esters. A simplified linear in vivo model was found to inadequately describe the time course of urinary excretion over the entire sampling period. We represented the skin barrier as both a one layer (stratum corneum) and a two-layer (stratum corneum with viable epidermis) diffusion model and convoluted their Laplace solutions with that for a single exponential disposition phase to describe the urinary excretion profiles in the Laplace domain. We also derived asymptotic approximations for the model and estimated the conditions under which they could be used. We then sought to develop in vitro - in vivo relationships (IVIVR) for topically applied methyl, ethyl and glycol salicylates using our experimental IVPT data and the literature urinary excretion data. Good linear IVIVRs for ethyl and glycol salicylates were obtained, but the IVIVR for methyl salicylate was poor, perhaps because of topical stimulation of local skin blood flow by methyl salicylate. The ratio of the hydrated to dehydrated skin permeation for all salicylate esters was the same in both the IVPT and in vivo studies. A diffusion based one compartment pharmacokinetic model was also developed to describe the urinary excretion of solutes after removal of topical products and to compare the methyl salicylate skin permeation for five different body sites. The work presented here is consistent with the development of skin IVIVRs, but suggests that different skin conditions, application sites and local skin effects may affect model predictions.

Effects of Proximal Tubule Shortening on Protein Excretion in a Lowe Syndrome Model.

Lowe syndrome (LS) is an X-linked recessive disorder caused by mutations in OCRL, which encodes the enzyme OCRL. Symptoms of LS include proximal tubule (PT) dysfunction typically characterized by low molecular weight proteinuria, renal tubular acidosis (RTA), aminoaciduria, and hypercalciuria. How mutant OCRL causes these symptoms isn't clear. We examined the effect of deleting OCRL on endocytic traffic and cell division in newly created human PT CRISPR/Cas9 OCRL knockout cells, multiple PT cell lines treated with OCRL-targeting siRNA, and in orcl-mutant zebrafish. OCRL-depleted human cells proliferated more slowly and about 10% of them were multinucleated compared with fewer than 2% of matched control cells. Heterologous expression of wild-type, but not phosphatase-deficient, OCRL prevented the accumulation of multinucleated cells after acute knockdown of OCRL but could not rescue the phenotype in stably edited knockout cell lines. Mathematic modeling confirmed that reduced PT length can account for the urinary excretion profile in LS. Both ocrl mutant zebrafish and zebrafish injected with ocrl morpholino showed truncated expression of megalin along the pronephric kidney, consistent with a shortened S1 segment. Our data suggest a unifying model to explain how loss of OCRL results in tubular proteinuria as well as the other commonly observed renal manifestations of LS. We hypothesize that defective cell division during kidney development and/or repair compromises PT length and impairs kidney function in LS patients.