Human urinary excretion kinetics of the antimycotic climbazole: Biomonitoring of two new metabolites after oral and dermal dosage.

Climbazole is an antimycotic compound used in cosmetic products as a preservative or as an active ingredient in anti-dandruff (AD) formulations. In this study we provide human toxicokinetic data on climbazole. Using our previously published analytical method, we investigated the urinary excretion of two climbazole metabolites, (OH)2-climbazole and cx-OH-climbazole, for 48 h after oral ingestion (n = 5, 49-77 µg/kg bw) and for 72 h after dermal application of either a climbazole-containing rinse-off AD shampoo or a leave-on hair tonic (n = 2×3). In total, 23.9 % (18.0-33.4 %) of the oral dose were excreted as the two abovementioned metabolites over 48 h. In one volunteer, who used an over-the-counter phytopharmaceutical, metabolite excretion was about three times lower and we found influences on diastereoselectivity of (OH)2-climbazole formation using a modified analytical method. After dermal application, urinary concentration maxima occurred considerably later than after oral intake. The two different dermal exposure scenarios also revealed a relevance of exposure duration and product formulation on the systemic availability of climbazole. Back-calculated oral-dose-equivalent intakes from the dermal exposures showed a maximum climbazole intake of 18.5 µg/kg bw/d after hair tonic use, or 6.6 µg/kg bw/d after AD shampoo application.

Toxicokinetics of homosalate in humans after dermal application: applicability of oral-route data for exposure assessment by human biomonitoring.

Homosalate (HMS) is a UV filter used in sunscreens and personal care products as a mixture of cis- and trans-isomers. Systemic absorption after sunscreen use has been demonstrated in humans, and concerns have been raised about possible endocrine activity of HMS, making a general population exposure assessment desirable. In a previous study, it was shown that the oral bioavailability of cis-HMS (cHMS) is lower than that of trans-HMS (tHMS) by a factor of 10, calling for a separate evaluation of both isomers in exposure and risk assessment. The aim of the current study is the investigation of HMS toxicokinetics after dermal exposure. Four volunteers applied a commercial sunscreen containing 10% HMS to their whole body under regular-use conditions (18-40 mg HMS (kg bw)-1). Parent HMS isomers and hydroxylated and carboxylic acid metabolites were quantified using authentic standards and isotope dilution analysis. Further metabolites were investigated semi-quantitatively. Elimination was delayed and slower compared to the oral route, and terminal elimination half-times were around 24 h. After dermal exposure, the bioavailability of cHMS was a factor of 2 lower than that of tHMS. However, metabolite ratios in relation to the respective parent isomer were very similar to the oral route, supporting the applicability of the oral-route urinary excretion fractions for dermal-route exposure assessments. Exemplary calculations of intake doses showed margins of safety between 11 and 92 (depending on the approach) after single whole-body sunscreen application. Human biomonitoring can reliably quantify oral and dermal HMS exposures and support the monitoring of exposure reduction measures.

Identification, Organic Synthesis, and Sensitive Analysis of a cis-Homosalate-Specific Exposure Biomarker.

Homosalate (HMS) is an organic UV filter used in sunscreens and personal care products. Despite its widespread use and detection in environmental matrices, little is known regarding its exposure in humans. HMS is used as a mixture of cis- and trans-isomers, and we recently revealed major differences in human toxicokinetics, indicating the need to consider these isomers separately in exposure and risk assessments. In the course of these previous investigations of human HMS toxicokinetics, we identified two trans-HMS-specific and one cis-HMS-specific biomarker candidates. However, the latter lacks sensitivity due to only low amounts excreted in urine, prompting the search for another cis-HMS-specific biomarker. Our toxicokinetic investigations revealed a total of five isomers of HMS carboxylic acid metabolites (HMS-CA). Of these, only one was specifically formed from cis-HMS (HMS-CA 5), but its full identity in terms of constitution and configuration had, so far, not been elucidated. Here, we describe the synthesis of three HMS-CA isomers, of which the isomer (1R,3S,5S)/(1S,3R,5R)-3-((2-hydroxybenzoyl)oxy)-1,5-dimethylcyclohexane-1-carboxylic acid turned out to be HMS-CA 5. Taken together with two previously synthesized HMS-CA isomers, we were able to identify the constitution and configuration of all five HMS-CA isomers observed in human metabolism. We integrated the newly identified cis-HMS-specific metabolite HMS-CA 5 into our previously published human biomonitoring LC-MS/MS method. Intra- and interday precisions had coefficients of variation below 2% and 5%, respectively, and the mean relative recovery was 96%. The limit of quantification in urine was 0.02 µg L-1, enabling the quantification of HMS-CA 5 in urine samples for at least 96 h after sunscreen application. The extended method thus enables the sensitive and separate monitoring of cis- and trans-HMS in future human biomonitoring studies for exposure and risk assessment.

Increasing exposure to the UV filters octocrylene and 2-ethylhexyl salicylate in Germany from 1996 to 2020: Human biomonitoring in 24-h urine samples of the German Environmental Specimen Bank (ESB).

The UV filters octocrylene (OC) and 2-ethylhexyl salicylate (EHS) are commonly used in sunscreens and frequently detected in environmental media. However, knowledge on human exposures is scarce. In this human biomonitoring (HBM) study, we analyzed concentrations of exposure biomarkers specific to OC (CPAA, DOCCA, 5OH-OC) and EHS (5OH-EHS, 5oxo-EHS, 5cx-EPS) in 24-h urine samples (n = 420) from the German Environmental Specimen Bank (ESB). These samples were collected from German students (20-29 years; 30 males/30 females per year) between 1996 and 2020 (4-year intervals; collection in winter). We found continuously increasing OC and EHS exposures (Jonckheere-Terpstra; p < 0.001) documented by very few to no samples with concentrations of the most sensitive biomarkers CPAA and 5cx-EPS above the limit of quantification (LOQ) in 1996 (5 % and 0 %, respectively) and reaching 100 % and 93 % above the LOQ in 2016, with median concentrations of 4.79 and 0.071 µg/L, respectively. In 2020, biomarker concentrations slightly decreased to 3.12 µg/L CPAA (97 %>LOQ) and 0.060 µg/L 5cx-EPS (88 %>LOQ). This general trend was confirmed by the other biomarkers, however at lower detection rates. Based on metabolite excretion in the 24-h urine samples and human toxicokinetic data, we calculated maximum daily intakes (DI) of 17 µg/(kg bw * d) OC and 59 µg/(kg bw * d) EHS. Based on a derived no-effect level (DNEL) of 0.8 mg/(kg bw * d), the OC exposures of individuals in our study did not indicate any health risk. Similarly, for EHS all biomarker concentrations were well below the HBM-I values of 12 µg/L 5OH-EHS and 11 µg/L 5cx-EPS. Our data proves the general applicability of specific OC and EHS metabolites for HBM in the general population and shows clearly increasing exposures. Higher (co-)exposures must be expected in populations with increased sunscreen use such as (summer) vacationers, children and outdoor workers.

Diastereoselective metabolism of homomenthyl salicylate (homosalate): Identification of relevant human exposure biomarkers.

Homosalate (HMS) is a salicylate UV filter broadly used in sunscreens and personal care products. The aim of this study was the collection of human toxicokinetic data on HMS as a tool for risk assessment. For this purpose, metabolism and urinary excretion after a single oral HMS dose (98.2-149.1 µg (kg body weight)-1) were investigated in four volunteers (two male, two female). As commercial products generally contain a mixture of cis- and trans-HMS, both cis-rich and trans-rich isomer mixtures were studied to investigate possible differences in metabolism. Initial metabolite screening tentatively identified six oxidative metabolite subgroups, of which hydroxylated and carboxylic acid metabolites were studied in more detail. Unchanged parent HMS and the previously identified HMS metabolites 5-((2-hydroxybenzoyl)oxy)-3,3-dimethylcyclohexane-1-carboxylic acid (HMS-CA) and 3-hydroxy-3,5,5-trimethylcyclohexyl 2-hydroxybenzoate (3OH-HMS), respectively, were quantified separately as cis- and trans-isomers via authentic standards by isotope dilution analysis. In addition, further alkyl-hydroxylated and carboxylic acid metabolites were investigated semi-quantitatively. Peak concentrations in urine were reached 1.5-6.3 h post-dose and more than 80 % of each of the quantitatively investigated metabolites (and at least 70 % of the semi-quantitatively investigated metabolites) was excreted within the first 24 h. Plasma and urine data indicated that oral bioavailability of cis-HMS was one order of magnitude below that of trans-HMS. Furthermore, the mean total urinary excretion fraction (Fue) for the metabolites derived from trans-HMS (6.4 %) was two orders of magnitude higher than for the metabolites derived from cis-HMS (0.045 %). Our data proves diastereoselectivity in toxicokinetics of cis- and trans-HMS, emphasizing the necessity to address isomer ratios in future studies including HMS exposure and risk assessments.

Determination of urinary metabolites of the UV filter homosalate by online-SPE-LC-MS/MS.

Homosalate (HMS) is an organic UV filter used in sunscreens and personal care products worldwide. It has been detected in various environmental matrices and in humans after application of HMS-containing products. However, sufficient data on the internal HMS exposure in humans is currently not available. Thus, we aimed at providing an analytical method for the sensitive determination of specific HMS metabolites in human urine. We describe the synthesis of analytical standards for the four oxidative HMS metabolites included in this method: 5-((2-hydroxybenzoyl)oxy)-3,3-dimethylcyclohexane-1-carboxylic acid (HMS-CA) and 3-hydroxy-3,5,5-trimethylcyclohexyl 2-hydroxybenzoate (3OH-HMS), as cis- and trans-isomers, respectively. After enzymatic hydrolysis, urine samples were analyzed using liquid chromatography-electrospray ionization-triple quadrupole-tandem mass spectrometry, including turbulent flow chromatography for online sample cleanup and analyte enrichment (online-SPE-LC-MS/MS). Quantification was performed by stable isotope dilution analysis, using deuterium-labeled HMS-CA as internal standards (cis and trans). Limits of quantification of 0.02-0.04 µg L-1 were sufficiently low to quantify the HMS metabolites for up to 96 h (trans-HMS-CA), 48 h (cis-HMS-CA and 3OH-trans-HMS), and 24 h (3OH-cis-HMS) after a pilot dermal application of a commercially available sunscreen in one human volunteer, showing clear elimination kinetics. Furthermore, in a German pilot population (n = 35), HMS metabolites were above the LOQ precisely in those three individuals who had applied sunscreen within the previous five days, thus corroborating the specificity of the identified metabolites as biomarkers of HMS exposure. The method is currently used in a human metabolism study and will be applied in future population-scale human biomonitoring studies.

The renal vasodilatory effect of prostaglandins is ameliorated in isolated-perfused kidneys of endotoxemic mice.

Endotoxemia-related acute kidney injury (AKI) is associated with increased formation of prostaglandins, which may serve as a compensatory mechanism to maintain renal function. We hypothesized that an increase of renal EP2 or EP4 receptors and/or a downregulation of renal EP1 and EP3 receptors enhances PGE2-induced renal vasodilatation. Injection of lipopolysaccharide (LPS; 3 mg/kg i.p.) increased microsomal prostaglandin E synthase (mPGES)-1 and prostacyclin synthase expression, whereas mPGES-2 expression was unaltered. Further, LPS increased the mRNA abundance for the prostaglandin EP4 receptor, whereas the expressions of the EP1 and EP3 receptors were decreased. In isolated-perfused kidneys from control mice, PGE2 exerted a dual effect on renal vascular tone, inducing vasodilatation at lower concentrations and vasoconstriction at higher concentrations. In kidneys from endotoxemic mice, the vasodilatory component was more pronounced, whereas the vasoconstriction at higher PGE2 concentrations was absent. Similarly, prostacyclin (PGI2)-induced vasodilatation was more pronounced in endotoxemic kidneys. The enhanced vasodilatory effect was paralleled by an increase in renal vascular EP4 and prostacyclin IP receptor mRNA expression. Further, stimulation of renin secretion rate by PGE2 and PGI2 was enhanced in endotoxemic kidneys. Pretreatment with the cyclooxygenase (COX)-2 inhibitor SC-236 (10 mg/kg) did not alter the basal GFR, but augmented the LPS-induced decline in GFR, and attenuated the LPS-induced increase in plasma renin concentration in vivo. Our data suggest that an activation of the COX-2/mPGES-1 synthetic pathway is responsible for the increased renal formation of PGE2 in response to LPS and that the vasodilatory effect of PGE2 and PGI2 is enhanced during endotoxemia.

Serum and Saliva Concentrations of Venlafaxine, O-Desmethylvenlafaxine, Quetiapine, and Citalopram in Psychiatric Patients.

BACKGROUND: Therapeutic drug monitoring has become increasingly important in psychiatric therapy. However, it is not yet implemented as a daily routine in clinical settings. To evaluate new, noninvasive procedures, we compared blood and saliva venlafaxine, quetiapine, and citalopram concentrations in samples collected from psychiatric patients. METHODS: We collected blood and saliva samples from 75 psychiatric patients (39 venlafaxine, 19 quetiapine, and 17 citalopram). Saliva sampling was achieved by the use of cotton pads. Venlafaxine (and its metabolite O-desmethylvenlafaxine) and quetiapine were analyzed by LC-MS/MS, whereas citalopram was analyzed by HPLC. RESULTS: We observed significant correlations between concentrations of venlafaxine (ratio saliva/serum ± SD: 18.3 ± 9.5, P < 0.01, r = 0.895) and its metabolite O-desmethylvenlafaxine (ratio saliva/serum ± SD: 4.1 ± 3.2, P < 0.05, r = 0.344), quetiapine (ratio saliva/serum ± SD: 0.2 ± 0.2, P < 0.01, r = 0.935), and citalopram (ratio saliva/serum ± SD: 2.6 ± 1.2, P < 0.05, r = 0.54) in serum and in saliva. Furthermore, measured concentrations of venlafaxine (and its metabolite O-desmethylvenlafaxine) and citalopram were higher in saliva than in serum, whereas measured concentrations of quetiapine were higher in serum than in saliva. CONCLUSIONS: Using cotton pad saliva sampling, venlafaxine and quetiapine demonstrate high correlations between saliva and serum concentrations, whereas for O-desmethylvenlafaxine and citalopram, other methods of sampling might be preferable. Saliva therapeutic drug monitoring of psychoactive drugs might become a useful approach to achieving individual treatment regimens.

A retrospective analysis of bone mineral status in patients requiring spinal surgery.

BACKGROUND: Impaired bone quality is associated with poor outcome of spinal surgery. The aim of the study was to assess the bone mineral status of patients scheduled to undergo spinal surgery and to report frequencies of bone mineral disorders. METHODS: We retrospectively analyzed the bone mineral status of 144 patients requiring spinal surgery including bone mineral density by dual-energy X-ray absorptiometry (DXA) as well as laboratory data with serum levels of 25-hydroxyvitamin D (25-OH-D), parathyroid hormone, calcium, bone specific alkaline phosphate, osteocalcin, and gastrin. High-resolution peripheral quantitative computed tomography (HR-pQCT) was additionally performed in a subgroup of 67 patients with T-Score below - 1.5 or history of vertebral fracture. RESULTS: Among 144 patients, 126 patients (87.5%) were older than 60 years. Mean age was 70.1 years. 42 patients (29.1%) had suffered from a vertebral compression fracture. 12 previously undiagnosed vertebral deformities were detected in 12 patients by vertebral fracture assessment (VFA). Osteoporosis was present in 39 patients (27.1%) and osteopenia in 63 patients (43.8%). Only 16 patients (11.1%) had received anti-osteoporotic therapy, while 54 patients (37.5%) had an indication for specific anti-osteoporotic therapy but had not received it yet. The majority of patients had inadequate vitamin D status (73.6%) and 34.7% of patients showed secondary hyperparathyroidism as a sign for a significant disturbed calcium homeostasis. In a subgroup of 67 patients, severe vertebral deformities were associated with stronger deficits in bone microarchitecture at the distal radius compared to the distal tibia. CONCLUSIONS: This study shows that bone metabolism disorders are highly prevalent in elderly patients scheduled for spinal surgery. Vertebral deformities are associated with a predominant deterioration of bone microstructure at the distal radius. As impaired bone quality can compromise surgical outcome, we strongly recommend an evaluation of bone mineral status prior to operation and anti-osteoporotic therapy if necessary.

Anticoagulation strategies in venovenous hemodialysis in critically ill patients: a five-year evaluation in a surgical intensive care unit.

Renal failure is a common complication among critically ill patients. Timing, dosage, and mode of renal replacement (RRT) are under debate, but also anticoagulation strategies and vascular access interfere with dialysis success. We present a retrospective, five-year evaluation of patients requiring RRT on a multidisciplinary 50-bed surgical intensive care unit of a university hospital with special regard to anticoagulation strategies and vascular access. Anticoagulation was preferably performed with unfractionated heparin or regional citrate application (RAC). Bleeding and suspected HIT-II were most common causes for RAC. In CVVHD mode filter life span was significantly longer under RAC compared to heparin or other anticoagulation strategies (P=0.001). Femoral vascular access was associated with reduced filter life span (P=0.012), especially under heparin anticoagulation (P=0.015). Patients on RAC had higher rates of metabolic alkalosis (P=0.001), required more transfusions (P=0.045), and showed higher illness severity measured by SOFA scores (P=0.001). RRT with unfractionated heparin represented the most common anticoagulation strategy in this study population. However, patients with bleeding risk and severe organ dysfunction were more likely placed on RAC. Citrate provided longer filter life spans regardless of vascular access site. Attention has to be paid to metabolic disturbances.