Cenobamate (YKP3089) as adjunctive treatment for uncontrolled focal seizures in a large, phase 3, multicenter, open-label safety study.

OBJECTIVE: During the development of cenobamate, an antiseizure medication (ASM) for focal seizures, three cases of drug reaction with eosinophilia and systemic symptoms (DRESS) occurred. To mitigate the rate of DRESS, a start-low, go-slow approach was studied in an ongoing, open-label, multicenter study. Also examined were long-term safety of cenobamate and a method for managing the pharmacokinetic interaction between cenobamate, a 2C19 inhibitor, and concomitant phenytoin or phenobarbital. METHODS: Patients 18-70 years old with uncontrolled focal seizures taking stable doses of one to three ASMs were enrolled. Cenobamate 12.5 mg/d was initiated and increased at 2-week intervals to 25, 50, 100, 150, and 200 mg/d. Additional biweekly 50 mg/d increases to 400 mg/d were allowed. During titration, patients taking phenytoin or phenobarbital could not have their cenobamate titration rate or other concomitant ASMs adjusted; phenytoin/phenobarbital doses could be decreased by 25%-33%. RESULTS: At data cutoff (median treatment duration = 9 months), 1347 patients were enrolled, of whom 269 (20.0%) discontinued, most commonly due to adverse events (n = 137) and consent withdrawn for reason other than adverse event (n = 74); 1339 patients received ≥1 treatment dose (median modal dose = 200 mg). The most common treatment-emergent adverse events (TEAEs) were somnolence (28.1%), dizziness (23.6%), and fatigue (16.6%). Serious TEAEs occurred in 108 patients (8.1%), most commonly seizure (n = 14), epilepsy (n = 5), and pneumonia, fall, and dizziness (n = 4 each). No cases of DRESS were identified. In the phenytoin/phenobarbital groups, 43.4% (36/114) and 29.7% (11/51) of patients, respectively, had their doses decreased. At the end of titration, mean plasma phenytoin/phenobarbital levels were generally comparable to baseline. SIGNIFICANCE: No cases of DRESS were identified in 1339 patients exposed to cenobamate using a start-low (12.5 mg/d), go-slow titration approach. Cenobamate was generally well tolerated in the long term, with no new safety issues found. Phenytoin/phenobarbital dose reductions (25%-33%), when needed during cenobamate titration, maintained stable plasma levels.

Monolithic mixed matrix membrane based on polyethersulfone/functionalized MWCNTs nanocomposite as an SPME fiber: Application to extract chlorophenols from human urine and serum samples followed by GC-ECD.

A monolithic mixed matrix membrane of functionalized multi-walled carbon nanotubes-polyethersulfone (MWCNT/PES) was prepared in a non-covalent approach and employed as an SPME fiber for extraction of chlorophenols (CPs). The proposed extraction method was followed by GC-ECD to determine the analytes. The influencing factors on the extraction efficiency such as pH, ionic strength, extraction and desorption temperature and time were studied. Under the selected conditions, calibration curves were linear over a wide concentration range from 0.005 to 1000 µgL-1 (r2 > 0.9961) for target analytes. In addition, the limits of detection (LOD) of the method were obtained in the range of 0.3-30 ng L-1. The relative standard deviation (RSD) for single fiber repeatability (n = 5) is from 1.4 to 4.6%. Fiber-to-fiber repeatability (n = 3) was also evaluated and the RSD is in the range of 1.3-6.3%. Applications of proposed fiber for extraction of CPs from the headspace of urine and serum samples were successfully investigated. The relative recovery in the biological samples spiked with different levels of CPs were in the range of 91.6-102.5%.

Mass Balance, Metabolism, and Excretion of Cenobamate, a New Antiepileptic Drug, After a Single Oral Administration in Healthy Male Subjects.

BACKGROUND AND OBJECTIVE: Cenobamate is an antiepileptic drug for the treatment of partial-onset seizures. The current study was designed to assess the mass balance and the metabolic profiling of cenobamate in humans. METHODS: Absorption, metabolism, and excretion of cenobamate were investigated in healthy male subjects after a single oral dose of 400 mg of cenobamate containing 50 µCi of [14C]-cenobamate as capsule formulation. RESULTS: Cenobamate was rapidly (median time to maximum plasma concentration of 1.25 h) and extensively (≥ 88% of dose) absorbed. The mean cenobamate plasma concentration-time profile revealed a multiphasic elimination profile whereas the mean plasma/blood concentration-time curve for total radioactivity did not appear to be multiphasic, suggesting that elimination mechanisms for cenobamate and its metabolites may be different. Blood/plasma ratios observed for the area under the concentration-time curve (AUC) and peak concentration (both ~ 0.60) suggest a limited penetration of cenobamate and metabolites into red blood cells (RBCs). Eight cenobamate metabolites were identified across plasma, urine, and feces. Cenobamate was the main plasma radioactive component and M1 was the only metabolite detected in plasma (> 98% and < 2% total radioactivity AUC, respectively). All detected metabolites were found in urine, with M1 as the major radioactive component (mean cumulative recovery 37.7% of dose); unchanged cenobamate accounted for 6%. Metabolites comprised ~ 88% of the dose recovered in urine, indicating extensive metabolism by the kidneys and/or metabolites formed in the liver were rapidly eliminated from the bloodstream. However, cenobamate metabolites appear to be formed slowly. Minor amounts of cenobamate (0.48%) and five metabolites (≤ 1.75% each; M1, M3, M6, M7, M11) were recovered in feces. CONCLUSION: This study indicates that cenobamate is primarily eliminated in urine as metabolites. Cenobamate is the major circulating component in plasma after oral administration and has a limited penetration into RBCs.

Cenobamate for the treatment of focal epilepsies.

INTRODUCTION: Antiseizure drugs (ASDs) play a central and crucial role in the treatment of epilepsy patients because the majority require anticonvulsant treatment for an extended period of time. Due to the fact that 30% of patients are refractory to medical treatment, new therapeutic options are necessary. Cenobamate is the latest approved antiepileptic drug in focal epilepsy, and its mode of action is thought to be mediated by blocking voltage-gated sodium channels and interaction with the GABAergic system. AREAS COVERED: This article reviews animal studies, pharmacokinetics, pharmacodynamics, and the phase 1 to 3 trials and open-label extension data on cenobamate. EXPERT OPINION: Cenobamate has the potential to perform as an important ASD because trial data are indicative of remarkable responder and seizure freedom rates so far not seen with other ASDs. Cenobamate demonstrated significant efficacy at a dosage between 100 and 400 mg per day. The side-effect profile of this drug is comparable to other ASDs and is mainly CNS related; in particular, somnolence, dizziness, headache, diplopia, and nystagmus. However, slow titration is mandatory to decrease the risk of drug rash with eosinophilia and systemic symptoms (DRESS) that was observed in several patients with fast uptitration schemes.

Validation of a prediction model for estimating serum concentrations of chemicals which are equivalent to toxic concentrations in vitro.

The objective of the present study was to evaluate the validity of a recently developed extrapolation model for the prediction of concentrations of chemicals in serum which are equivalent to in vitro effective nominal concentrations. Necessary input data are in vitro toxic concentrations and distribution relevant system and substance specific parameters, e.g. lipid volume fractions and albumin concentrations, octanol/water partition coefficients and specific binding to albumin. It was investigated whether the influence of human and bovine serum, respectively, on nominal cytotoxic potencies (EC(50)-values) of selected chemicals in vitro can be properly predicted using this algorithm. Cytotoxicity was determined as growth inhibition of proliferating Balb/c 3T3 cells after exposure for 72 h. Concentration-effect relationships were measured in the presence of 2% foetal bovine serum (FBS) and, additionally, 18% FBS or human serum (HS), or 1% (w/v) bovine (BSA) or human (HSA) albumin, respectively. Addition of HSA and BSA increased the EC(50)-values of the different chemicals by factors of 2.1 - 22 and 1.7 - 29, respectively. From these measurements values for the specific binding of the test compounds to BSA and HSA were derived. Addition of 18% HS increased the EC(50)-values by factors between 4.2 and 52, while addition of 18% FBS resulted only in 1.5 - 10.4-fold increases. A comparison of experimentally determined and calculated EC(50)-values revealed that the differing influence of human and bovine serum was quite well predicted by the extrapolation model. Deviations did not exceed the factor 3 and were in most cases lower than 2. It is concluded that the extrapolation model is quite well suited to predict equivalent concentrations in serum from in vitro effective concentrations.

Environmental chemicals mediated the effect of old housing on adult health problems: US NHANES, 2009-2010.

Housing conditions affect occupants continuously, and health interventions have shown a positive association between housing investment or improvement and occupant's health. However, the sources of the housing problems were less understood. Since it was observed that lead dust and chloroanisoles released from housing (materials) as indoor pollutants affected child's health, we now aimed to examine the relationships among built year, environmental chemicals and individual health in adults in a national and population-based setting. Data were retrieved from the US National Health and Nutrition Examination Survey, 2009-2010, including demographics, housing characteristics, self-reported health status, biomarkers and blood and urinary chemical concentrations. Adults aged 20 and above were included for statistical analysis (n = 5,793). Analysis involved chi-square test, t test, and survey-weighted general linear regression and logistic regression modelling. People who resided in older housing built before 1990 tended to report chronic bronchitis, liver problems, stroke, heart failure, diabetes, asthma and emphysema. Higher values in HDL cholesterol, blood lead and blood cadmium and having positive responses of hepatitis A, B, C and E antibodies among occupants were also observed. Furthermore, higher environmental chemical concentrations related to old housing including urinary cadmium, cobalt, platinum, mercury, 2,5-dichlorophenol and 2,4-dichlorophenol concentrations and mono-cyclohexyl phthalate and mono-isobutyl phthalate metabolites were shown in occupants as well. Older housing (≥30 years) seemed to contribute to the amount of environmental chemicals that affected human health. Regular monitoring, upgrading and renovation of housing to remove environmental chemicals and policy to support people in deprived situations against environmental injustice would be needed.

Effects of halogenated antibacterials on the erythrocyte membrane.

The influence of halogenated antibacterials on membrane structure and function was investigated using the human erythrocyte membrane as a model. Measurements of hemolysis in isotonic solution, altered membrane permeability, and stabilization against hypotonic hemolysis resulting from exposure of erythrocytes to halogenated antibacterials served as criteria of membrane-related effects. The hemolytic potency of the compounds studied differed widely, decreasing in the order hexachlorophene (HCP) greater than 2,2'-methylenebis(3,5-dichlorophenol) (3,5-TCP) greater than 2,2'-methylenebis(3,4-dichlorophenol) (3,4-TCP) approximately equal to 2,2'-methylenebis(4,6-dichlorophenol) (4,6-TCP) greater than 2,2'-methylenebis(4-chlorophenol) (DCP) greater than 3,4'-tribromosalicylanilide (TBS) approximately equal to 3,3',4',5-tetrachlorosalicylanilide (TCSA). Each of the antibacterials tested stabilized the erythrocyte against hypotonic hemolysis, although there were marked differences in the concentrations required to afford maximum stabilization as well as in the extent of protection. The observed order of protective effectiveness was HCP greater than 3,4-TCP greater than 4,6-TCP greater than DCP approximately equal to TCS greater than TBS. As shown by measurements of the first-order rate constant for K+ efflux, the permeability of the erythrocyte membrane to K+ was increased upon exposure to the antibacterials, with the effect of HCP greater than 3,4-TCP greater than 4,6-TCP approximately equal to 3,4-TCP greater than DCP approximately equal to TCS greater than TBS. These results indicate that halogenated antibacterials are capable of perturbing mammalian membranes, a feature which may account in part for their mammalian toxicity.

Binding of selected phenol derivatives to human serum proteins.

The binding of phenol and four of its derivatives to whole human serum and several human serum proteins was investigated. 14C-labeled derivatives were utilized and binding was studied by either equilibrium or dynamic dialysis. Phenol itself was bound least to most of the serum proteins as compared to the derivatives and albumin, and whole human serum exhibited the highest percent binding of the proteins used. Percent binding to albumin and serum paralleled molecular weights of the derivatives, but not definite pattern was observed in ranking the percent binding of the other derivatives to the other serum proteins. Binding constants (K1, K2, n1 and n2) were determined from Scatchard plots for all the derivatives except p-chloro-m-xylenol. Phenol was found to have the highest association constant (K1) and p-tert-amylphenol, the lowest. For the entire group of five derivatives and albumin as the protein, a direct, statistically significant correlations was found between percent binding and Hansch pi values. No correlation was found with Hammett sigma values. It is concluded that binding of the phenol derivatives to albumin involves primarily hydrophobic bonds.

Plasma pentachlorophenol concentrations in calves exposed to treated wood in the environment.

Six calves were fed grain and hay from a pentachlorophenol (PCP)-treated feeder twice daily. Samples of blood were collected twice a week. Plasma PCP concentrations increased rapidly to a maximum of 1,086 microgram/L within 10 days. After the 3rd week, calves were denied access to the treated feeder; PCP values returned rapidly to near base line (before calves were fed from the treated feeder). After base-line plasma PCP values were reached, 4 of the 6 calves were housed in a total confinement building and exposed (by inhalation) to lumber that was commercially treated with PCP. The building itself was free of structural PCP-treated lumber. The ratio of building volume to treated wood surface was approximately 49 to 1. During the 3 weeks the calves were confined, PCP values did not increase and were markedly lower than those associated with oral exposure to treated wood. Oral dosing of calves with PCP in capsules--0.05 and 0.5 mg/kg--resulted in maximal plasma PCP values of 1,449 and 9,555 micrograms/L, respectively. Oral exposures (feeding from contaminated feeder; capsule) appeared to be more important than inhalation in causing increased plasma PCP concentrations in cattle. Exposure from these sources may be estimated by comparison with experimental values from dose-response studies. Feeding from treated feeders resulted in lower plasma PCP values than did dosing with 0.05 mg/kg daily.

Stability of the conjugated species of environmental phenols and parabens in human serum.

In humans, the metabolism of environmental phenols may include the formation of conjugated species (e.g., glucuronides and sulfates), but the free species-not the conjugated forms-are considered biologically active. Therefore, information on the concentration of these free species in blood or urine could be helpful for risk assessment. Because conjugates could hydrolyze to their corresponding free forms during collection, handling, and storage of biological specimens, information on the temporal stability of the conjugates is of interest. Previously, we reported the temporal stability of urinary conjugates of several environmental phenols, but data on the stability of phenols' conjugated species in serum, albeit critical if concentrations of free and conjugated species are compared, are largely unknown. In the present study, we investigate the stability of the conjugates of four phenols-bisphenol A, benzophenone-3, triclosan, and 2,5-dichlorophenol-and two parabens-methyl paraben and propyl paraben-in 16 human serum samples for 30 days at above-freezing temperature storage conditions (4 degrees C, room temperature, and 37 degrees C). These conditions reflect the worst-case scenarios that could occur during the short-term storage of biological samples before their long-term storage at controlled subfreezing temperatures. We found that the percentage of the conjugated species of the four detected compounds (2,5-dichlorophenol, triclosan, and methyl and propyl parabens) in these serum specimens even when stored at 37 degrees C for at least 30 days did not vary significantly. These preliminary data suggest that the phenols' serum conjugates appear to be more stable than their corresponding urinary conjugates, some of which started to hydrolyze within 24h under similar storage conditions. The reported stability of these conjugated species in human serum also suggests that the free species are unlikely to have resulted from the hydrolysis of their corresponding conjugates. This information could be important for interpreting the low concentrations of free phenol species detected in serum samples of nonoccupationally exposed populations. To our knowledge, this is the first study to report on the stability of conjugated species in serum, and as such requires replication.

Factors related to dioxin and furan body levels among Michigan workers.

We evaluated serum concentrations of five selected dioxin, furan, and polychlorinated biphenyls (PCB) congeners among 412 workers at a Midland, Michigan plant that manufactured trichlorophenol and pentachlorophenol (PCP) and formulated chlorophenol-based products. We examined occupational indicators of exposure to these chlorophenols taking into account intrinsic factors such as age and body fat and potential environmental sources of exposure from consumption of local game and fish and other occupations. All five congeners were significantly associated with age and body fat. 2378-TCDD serum concentrations were associated with trichlorophenol operations, total years employed at the plant, as well as working as a hazardous waste worker. 123678-H(6)CDD serum concentrations were related to occupational PCP exposure, chloracne, recent weight loss, eating local game, and working as a hazardous waste worker. Serum concentrations of PCB126 were related to smoking (inversely), and eating local fish or local game. Other factors such as diet and jobs outside of the chlorophenol plant exposures had only a very minor impact on dioxin and furan concentrations in these workers.

Urinary excretion of chlorinated phenols in saw-mill workers.

The excretion and conjugation of chlorophenols were studied in workers exposed to 2,4,6-tri-, 2,3,4,6-tetra-, and pentachlorophenolates, the main components of the chlorophenolate product manufactured by direct chlorination of phenol. The workers were exposed in two different saw mills in which sodium chlorophenolate was used for treatment of lumber during the warm season. Urine specimens were collected at the end of the treatment season as well as at the start of a new treatment period in the spring. Serum specimens were collected towards the end of the treatment period. Total and unconjugated chlorophenols were analyzed with a gas chromatographic method. The maximal concentrations of urinary 2,4,6-tri-, 2,3,4,6-tetra- and pentachlorophenol at the end of the lumber-treatment period were 1-11.8, 3.4-17.3, and 0.2-0.9 mumol/l, respectively, and the average apparent half-times calculated using a one-compartment model were 18 h, 4.3 days and 16 days, respectively. For 2,3,4,6-tetrachlorophenol, the data of some subjects showed a better fit with a two-compartment model; the corresponding half-times were 5.3 and 26 days. During the continuous-exposure period the average serum levels of tetra- and pentachlorophenol were rather similar before and after the working day: 2.79 +/- 1.78 mumol/l for tetrachlorophenol and 0.85 +/- 0.4 mumol/l for pentachlorophenol. Renal clearance values for tetra- and pentachlorophenol were related to urine flow and indicated tubular reabsorption. At low concentrations, sulfate conjugation was dominant. With increasing chlorophenol concentrations the proportion of glucuronide conjugation was increased, especially for pentachlorophenol.

Determination of the GABAergic antidepressant drug fengabine and some of its metabolites in plasma by capillary gas chromatography with electron-capture detection.

A sensitive capillary gas chromatographic method was developed for the determination of fengabine (a GABAergic antidepressant drug) and some of its metabolites in plasma samples. The method involves a single and rapid liquid-liquid extraction of the parent drug and metabolites from plasma buffered at pH 5, evaporation of the organic phase under nitrogen, derivatization to tert.-butyldimethylsilyl ethers and esters and automatic gas chromatography on a fused-silica, silicone-bonded capillary column coupled to an electron-capture detector. The detection limit for fengabine and other compounds is lower than 1 ng/ml in plasma; the method was successfully applied to pharmacokinetic and drug monitoring clinical studies and tested on more than 2000 biological samples and was found not to suffer from endogenous or exogenous interferences.

On-line supported liquid membrane-liquid chromatography with a phenol oxidase-based biosensor as a selective detection unit for the determination of phenols in blood plasma.

The potential of on-line combination of supported liquid membrane extraction and column liquid chromatography with a phenol oxidase-based biosensor as a selective detection unit has been investigated for the determination of phenols in human plasma. The phenols are selectively extracted into a porous PTFE (polytetraflouroethene) membrane impregnated with a water-immiscible organic solvent and further into an alkaline acceptor phase. Via an ion-exchange interface, the analytes are transferred to a reversed-phase column where they are separated and detected using the biosensor. No sample pretreatment before the extraction, except centrifugation, is made. Due to the high selectivity both in the extraction and in the detection steps and to the fact that the demands on the chromatographic separation are low, a quick separation using an eluent with a low concentration of organic modifier can be made, without affecting the biosensor response. Detection limits below the 50 microg/l level in blood plasma were obtained for the three model compounds, phenol, p-cresol and 4-chlorophenol.

Absorption study of pentachlorophenol in persons working with wood preservatives.

Plasma and urinary pentachlorophenol (PCP) was measured in 209 workers who had occupational exposure to wood preservatives containing this compound and 101 workers not exposed occupationally to PCP. Workers were examined for chloracne and blood concentrations of bilirubin, gamma-glutamyltransferase (GGT), cholesterol and high-density lipoproteins (HDL) were determined. All the occupationally exposed groups showed evidence of PCP absorption; highest mean concentrations were found in remedial timber-treatment operatives (6.0 mmol/l for plasma and 274 nmol/mmol of creatinine for urine). Timber-yard workers also showed substantial evidence of absorption (mean plasma concentration 4.8 mmol/l). Persons formulating PCP-containing wood preservatives had the lowest concentrations of any exposed group sampled (mean plasma concentration 1.3 mmol/l, mean urinary concentration 39.6 nmol/mmol of creatinine). The occupational groups studied were not standardized for factors known to affect bilirubin, GGT, cholesterol and HDL. The inference that can be drawn from the results of these measurements is therefore limited. There was, however, no evidence of any disadvantageous effect of PCP on health as measured by these parameters. No overt case of chloracne was found.

Kinetics of 2,4,6-trichlorophenol in different organs of the rat.

The concentration of 2,4,6-trichlorophenol was measured in the blood and various other tissues of the rat after IP administration of the compound at 25 mg per kg body weight. The highest concentration, 329 +/- 117 nmol X g-1, was found in the kidney. Half-times were between 1.4 and 1.8 h in the blood, brain, fat, kidney, liver and muscle. The extent of conjugation of 2,4,6-trichlorophenol was also investigated by measuring total and free chlorophenol in the blood.

Plasma binding of 1-butanol, phenol, nitrobenzene and pentachlorophenol in the rainbow trout and rat: a comparative study.

1. The in vitro binding of 1-butanol, phenol, nitrobenzene, and pentachlorophenol in trout plasma and rat plasma was determined. 2. Binding to rainbow trout plasma proteins agreed within 9% of that observed in rat plasma. 3. Percentage bound to rainbow trout (2-99%) or rat (10-99%) plasma proteins increased as the log octanol/water partition coefficient of the chemicals increased within the Log P 1-3 range, and was suggestive of hydrophobic interactions in binding.

Occupational exposure to chlorophenates: toxicology and respiratory effects.

We have identified 71 chlorophenate-exposed sawmill workers as part of a group undergoing an extensive health and environmental evaluation in a pulp mill. We have compared this group with a group (351) with no physical proximity to the area in which chlorophenates were used. We demonstrated a gradient of exposure from 230 ppb in urine and 919 ppb in serum for those directly handling the contaminated wood, to 139 ppb in urine and 354 ppb in serum for those working in the area but not in manual contact as compared with serum levels of 84 ppb in the unexposed group. We noted that the bulk chemical was primarily in the tetrachloro-form but the serum levels contained more pentachlorophenate. The urine proportions were intermediate, approximating the bulk chemical proportions at the lower levels of exposure. We did not find an excess prevalence of respiratory symptoms or spirometric abnormalities which could be explained by the chlorophenate exposure.