Drug-drug interaction between diclofenac and gamma-hydroxybutyric acid.

Gamma hydroxybutyric acid (GHB) has been approved clinically to treat excessive daytime sleepiness and cataplexy in patients with narcolepsy, alcohol and opioid withdrawal, and as an anesthetic. The use of GHB clinically is limited due to its high abuse potential. The absorption, clearance and tissue uptake of GHB is mediated by proton-dependent and sodium-coupled monocarboxylate transporters (MCTs and SMCTs) and inhibition of these transporters may result in a change in GHB pharmacokinetics and pharmacodynamics. Previous studies have reported that non-steroidal anti-inflammatory drugs (NSAIDs) may inhibit these monocarboxylate transporters. Therefore, the purpose of this work was to analyze the interaction between GHB (at a dose of 600 mg/kg i. v.) and the NSAID, diclofenac, by examining the effects of this drug on the in vivo pharmacokinetics and pharmacodynamics in rat studies. The pharmacodynamic effect evaluated was respiratory depression, a measure of toxicity observed by GHB at this dose. There was an improvement in the respiratory rate with diclofenac administration suggesting an effect of diclofenac on GHB toxicity. In vitro studies with rat blood brain endothelial cells (RBE4) that express MCT1 indicated that diclofenac can inhibit GHB transport with an IC50 of 10.6 µM at pH 7.4. In vivo studies found a decrease in brain GHB concentrations and a decrease in the brain-to-plasma concentration ratio following diclofenac treatment. With this study we can conclude that diclofenac and potentially other NSAIDs can inhibit the transport of GHB into the brain, therefore decreasing GHB's pharmacodynamic effects and toxicity.

Development and validation of volumetric absorptive microsampling coupled with UHPLC-MS/MS for the analysis of gamma-hydroxybutyric acid in human blood.

A volumetric microsampling (VAMS) device (20 µl) was evaluated and validated for the analysis of γ-hydroxybutyric acid (GHB) in venous blood using a simple ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. GHB was extracted from VAMS device by acetonitrile, after a re-hydration step in a temperature-controlled ultrasonic bath at 60°C for 10 min. Chromatographic analysis was carried out on a Kinetex C18 column using 0.1% formic acid in water and acetonitrile as binary gradient mobile phase (from 5 to 95% of acetonitrile from 1 to 2.5 min) at a flow rate of 0.3 ml/min. The VAMS method was fully validated according to current guidelines with satisfactory results in terms of linearity, selectivity, precision, absolute recovery, matrix effect and stability. The linearity was determined from 0.5 to 200 µg/ml and the lower limit of quantitation was 0.5 µg/ml. The novel VAMS-UHPLC-MS/MS method was successfully compared with plasma-based method in a GHB-treated patient as a proof of concept.

Treatment of γ-Hydroxybutyric Acid and γ-Butyrolactone Overdose with Two Potent Monocarboxylate Transporter 1 Inhibitors, AZD3965 and AR-C155858.

The illicit use of γ-hydroxybutyric acid (GHB), and its prodrug, γ-butyrolactone (GBL), results in severe adverse effects including sedation, coma, respiratory depression, and death. Current treatment of GHB/GBL overdose is limited to supportive care. Recent reports indicate that GHB-related deaths are on the rise; a specific treatment may reduce lethality associated with GHB/GBL. Pretreatment with inhibitors of monocarboxylate transporter 1 (MCT1), a transporter that mediates many of the processes involved in the absorption, distribution (including brain uptake), and elimination of GHB/GBL, has been shown to prevent GHB-induced respiratory depression by increasing the renal clearance of GHB. To identify whether MCT1 inhibition is an effective treatment of GHB overdose, the impact of two MCT1 inhibitors, (S)-5-(4-hydroxy-4-methylisoxazolidine-2-carbonyl)-1-isopropyl-3-methyl-6-((3-methyl-5-(trifluoromethyl)-1H-pyrazol-4-yl)methyl)thieno[2,3-day]pyrimidine-2,4(1H,3H)-dione (AZD3965) and 6-[(3,5-dimethyl-1H-pyrazol-4-yl)methyl]-5-[[(4S)-4-hydroxy-2-isoxazolidinyl]carbonyl]-3-methyl-1-(2-methylpropyl)thieno[2,3-day]pyrimidine2,4(1H,3H)-dione (AR-C155858), on the toxicokinetics and toxicodynamics of GHB/GBL was assessed when the administration of the inhibitor was delayed 60 and 120 minutes (post-treatment) after administration of GHB/GBL. AR-C155858 and AZD3965 reduced the toxicodynamic effects of GHB when GHB was administered intravenously, orally, or orally as the prodrug GBL. The impact of these inhibitors on GHB toxicokinetics was dependent on the route of GHB administration and the delay between GHB/GBL administration and administration of the MCT1 inhibitor. The reduction in GHB plasma exposure did not explain the observed effect of MCT1 inhibition on GHB-induced respiratory depression. The efficacy of MCT1 inhibition on GHB toxicodynamics is likely driven by the pronounced reduction in GHB brain concentrations. Overall, this study indicates that inhibition of MCT1 is an effective treatment of GHB/GBL overdose.

Effects of renal impairment on transporter-mediated renal reabsorption of drugs and renal drug-drug interactions: A simulation-based study.

Renal impairment (RI) significantly impacts the clearance of drugs through changes in the glomerular filtration rate, protein binding and alterations in the expression of renal drug transport proteins and hepatic metabolizing enzymes. The objectives of this study were to evaluate quantitatively the effects of renal impairment on the pharmacokinetics of drugs undergoing renal transporter-mediated reabsorption. A previously published semi-mechanistic kidney model incorporating physiologically relevant fluid reabsorption and transporter-mediated active renal reabsorption (PMID: 26341876) was utilized in this study. The probe drug/transporter pair utilized was γ-hydroxybutyric acid (GHB) and monocarboxylate transporter 1 (SCL16A1, MCT1). γ-Hydroxybutyric acid concentrations in the blood and amount excreted into urine were simulated using ADAPT 5 for the i.v. dose range of 200-1500 mg/kg in rats and the impact of renal impairment on CLR and AUC was evaluated. A 90% decrease in GFR resulted in a > 100-fold decrease in GHB CLR . When expression of reabsorptive transporters was decreased and fu was increased, CLR approached GFR. The effect of renal impairment on CLR was reduced when the expression of drug metabolizing enzymes (DME) was increased as a result of increased metabolic clearance; the converse held true when the DME expression was decreased. In conclusion, this study quantitatively demonstrated that the effects of renal insufficiency on the clearance of drugs is modulated by transporter expression, contribution of renal clearance to overall clearance, expression of drug metabolizing enzymes, fraction unbound and drug-drug interactions with inhibitors of renal transporters that may be increased in the presence of renal impairment.

Semi-mechanistic kidney model incorporating physiologically-relevant fluid reabsorption and transporter-mediated renal reabsorption: pharmacokinetics of γ-hydroxybutyric acid and L-lactate in rats.

This study developed a semi-mechanistic kidney model incorporating physiologically-relevant fluid reabsorption and transporter-mediated active reabsorption. The model was applied to data for the drug of abuse γ-hydroxybutyric acid (GHB), which exhibits monocarboxylate transporter (MCT1/SMCT1)-mediated renal reabsorption. The kidney model consists of various nephron segments--proximal tubules, Loop-of-Henle, distal tubules, and collecting ducts--where the segmental fluid flow rates, volumes, and sequential reabsorption were incorporated as functions of the glomerular filtration rate. The active renal reabsorption was modeled as vectorial transport across proximal tubule cells. In addition, the model included physiological blood, liver, and remainder compartments. The population pharmacokinetic modeling was performed using ADAPT5 for GHB blood concentration-time data and cumulative amount excreted unchanged into urine data (200-1000 mg/kg IV bolus doses) from rats [Felmlee et al (PMID: 20461486)]. Simulations assessed the effects of inhibition (R = [I]/KI = 0-100) of renal reabsorption on systemic exposure (AUC) and renal clearance of GHB. Visual predictive checks and other model diagnostic plots indicated that the model reasonably captured GHB concentrations. Simulations demonstrated that the inhibition of renal reabsorption significantly increased GHB renal clearance and decreased AUC. Model validation was performed using a separate dataset. Furthermore, our model successfully evaluated the pharmacokinetics of L-lactate using data obtained from Morse et al (PMID: 24854892). In conclusion, we developed a semi-mechanistic kidney model that can be used to evaluate transporter-mediated active renal reabsorption of drugs by the kidney.

Phase 1 dose-escalation, pharmacokinetic, and cerebrospinal fluid distribution study of TAK-285, an investigational inhibitor of EGFR and HER2.

INTRODUCTION: This phase 1 study assessed safety, maximum tolerated dose (MTD), pharmacokinetics, cerebrospinal fluid (CSF) distribution, and preliminary clinical activity of the receptor tyrosine kinase inhibitor TAK-285. METHODS: Patients with advanced, histologically confirmed solid tumors and Eastern Cooperative Oncology Group performance status ≤2 received daily oral TAK-285; daily dose was escalated within defined cohorts until MTD and recommended phase 2 dose (RP2D) were determined. Eleven patients were enrolled into an RP2D cohort. Blood samples were collected from all cohorts; CSF was collected at pharmacokinetic steady-state from RP2D patients. Tumor responses were assessed every 8 weeks per Response Evaluation Criteria in Solid Tumors. RESULTS: Fifty-four patients were enrolled (median age 60; range, 35-76 years). The most common diagnoses were cancers of the colon (28 %), breast (17 %), and pancreas (9 %). Escalation cohorts evaluated doses from 50 mg daily to 500 mg twice daily; the MTD/RP2D was 400 mg twice daily. Dose-limiting toxicities included diarrhea, hypokalemia, and fatigue. Drug absorption was fast (median time of maximum concentration was 2-3 h), and mean half-life was 9 h. Steady-state average unbound CSF concentration (geometric mean 1.54 [range, 0.51-4.27] ng/mL; n = 5) at the RP2D was below the 50 % inhibitory concentration (9.3 ng/mL) for inhibition of tyrosine kinase activity in cells expressing recombinant HER2. Best response was stable disease (12 weeks of nonprogression) in 13 patients. CONCLUSIONS: TAK-285 was generally well tolerated at the RP2D. Distribution in human CSF was confirmed, but the free concentration of the drug was below that associated with biologically relevant target inhibition.

Synthesis and characterization of novel quick-release propofol prodrug via lactonization.

The water-soluble derivatives of propofol have gained attention as a method to increase solubility of propofol. According to the principle of lactonization, the lead compound HX0969 was synthesized first and then the pharmacological features of HX0969 were evaluated in a comparison with those of propofol in the SD rats. Then, HX0969 disodium phosphate monoester (HX0969W) and glycine ester trifluoroacetic acid salt (HX101230) were synthesized, and their pharmacological features were compared with those of Lusedra®, which has been recognized and marketed as a water-soluble prodrug of propofol since 2008. The results showed that HX0969 could produce an anesthetic effect within a few seconds (3.6±3.0s) and its therapeutic index was 4.66 in the SD rat. The pharmacodynamic characteristics of HX0969W were similar to those of the Lusedra®. HX101230 could still produce an anesthetic effect within 60s in the rats though its therapeutic index was not so high (TI=2.96). Therefore, our study has indicated that HX0969 is a potentially useful lead compound of propofol derivative. Its rapid anesthetic effect is probably associated with lactonization.

Cytotoxicity and antitumour activity of 5-fluorouracil-loaded polyhydroxybutyrate and cellulose acetate phthalate blend microspheres.

Pharmacokinetics, biodistribution and antitumour activity of 5-fluorouracil (5-FU)-loaded polyhydroxybutyrate (PHB) and cellulose acetate phthalate (CAP) blend microspheres were investigated in chemically induced colorectal cancer in albino male Wistar rats and compared with pristine 5-FU given as a suspension. The microspheres were characterised for particle size, encapsulation efficiency, in vitro release and in vitro cytotoxicity on human HT-29 colon cancer cell line. Spherical particles with a mean size of 44 ± 11 µm were obtained that showed sustained release of 5-FU. A high concentration of 5-FU was achieved in colonic tissues and significant reduction in tumour volume and multiplicity were observed in animals treated with 5-FU-loaded microspheres. The decreased levels of plasma albumin, creatinine, leucocytopenia and thrombocytopenia were observed in animals for 5-FU microspheres compared to the standard 5-FU formulation. The results suggest the extended release of 5-FU from the PHB-CAP blend microspheres in colonic region to enhance the antitumour efficacy.

Radioactive holmium acetylacetonate microspheres for interstitial microbrachytherapy: an in vitro and in vivo stability study.

PURPOSE: The clinical application of holmium acetylacetonate microspheres (HoAcAcMS) for the intratumoral radionuclide treatment of solid malignancies requires a thorough understanding of their stability. Therefore, an in vitro and an in vivo stability study with HoAcAcMS was conducted. METHODS: HoAcAcMS, before and after neutron irradiation, were incubated in a phosphate buffer at 37°C for 6 months. The in vitro release of holmium in this buffer after 6 months was 0.5%. Elemental analysis, scanning electron microscopy, infrared spectroscopy and time of flight secondary ion mass spectrometry were performed on the HoAcAcMS. RESULTS: After 4 days in buffer the acetylacetonate ligands were replaced by phosphate, without altering the particle size and surface morphology. HoAcAcMS before and after neutron irradiation were administered intratumorally in VX2 tumor-bearing rabbits. No holmium was detected in the faeces, urine, femur and blood. Histological examination of the tumor revealed clusters of intact microspheres amidst necrotic tissue after 30 days. CONCLUSION: HoAcAcMS are stable both in vitro and in vivo and are suitable for intratumoral radionuclide treatment.

Kinetics, safety and tolerability of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate in healthy adult subjects.

Induction of mild states of hyperketonemia may improve physical and cognitive performance. In this study, we determined the kinetic parameters, safety and tolerability of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate, a ketone monoester administered in the form of a meal replacement drink to healthy human volunteers. Plasma levels of ß-hydroxybutyrate and acetoacetate were elevated following administration of a single dose of the ketone monoester, whether at 140, 357, or 714 mg/kg body weight, while the intact ester was not detected. Maximum plasma levels of ketones were attained within 1-2h, reaching 3.30 mM and 1.19 mM for ß-hydroxybutyrate and acetoacetate, respectively, at the highest dose tested. The elimination half-life ranged from 0.8-3.1h for ß-hydroxybutyrate and 8-14 h for acetoacetate. The ketone monoester was also administered at 140, 357, and 714 mg/kg body weight, three times daily, over 5 days (equivalent to 0.42, 1.07, and 2.14 g/kg/d). The ketone ester was generally well-tolerated, although some gastrointestinal effects were reported, when large volumes of milk-based drink were consumed, at the highest ketone monoester dose. Together, these results suggest ingestion of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate is a safe and simple method to elevate blood ketone levels, compared with the inconvenience of preparing and consuming a ketogenic diet.

Pharmacokinetics and pharmacodynamics of A77 1726 and leflunomide in domestic cats.

The pharmacokinetics and pharmacodynamics of A77 1726 and leflunomide after intravenous (i.v.) and oral (p.o.) administration were evaluated in adult cats. Three treatments were administered: a single i.v. dose of A77 1726 (4 mg/kg), a single oral dose of leflunomide (4 mg/kg), and multiple oral doses of leflunomide (2 mg/kg). Mean pharmacokinetic parameter values after a single i.v. dose of A77 1726 were distribution (A) and elimination (B) intercepts (15.2 µg/mL and 34.5 µg/mL, respectively), distribution and elimination half-lives (1.5 and 71.8 h, respectively), area under the curve (AUC(0 → ∞); 3723 µg*h/mL), mean residence time (MRT; 93 h), clearance (Cl(obs); 1.1 mL/kg/h), and volume of distribution at steady state (Vd(ss); 97 mL/kg). Mean pharmacokinetic parameter values after a single oral dose of leflunomide were absorption and elimination rate constants (0.3 1/h and 0.01 1/h, respectively), absorption and elimination half-lives (2.3 and 59.1 h, respectively), AUC(0 → ∞) (3966 µg*h/mL), and maximum observed plasma concentration (C(max); 38 µg/mL). The bioavailability after a single oral dose of leflunomide was 100%. The mean ± SD A77 1726 concentration that inhibited 50% lymphocytes (EC(50) ) was 16 ± 13.5 µg/mL. The mean ± SD maximum A77 1726 concentration (EC(max)) was 61.0 ± 23.9 µg/mL.

[Current knowledge on gamma-hydroxybutyric acid (GHB), gamma-butyrolactone (GBL) and 1 ,4-butanediol (1,4-BD)]. / Données actuelles sur le GHB, la GBL et le 1,4-BD.

Gamma-hydroxybutyric acid (GHB) is an old anaesthetic drug which was misused in the 80-90's as an anabolic agent (bodybuilding), recreational drug (drunkenness, euphoric, disinhibiting and aphrodisiac effects) and as a date rape drug (disinhibiting, hypnotic and amnesic effects). Its use in the general population is low, and mainly concerns gay population in nightclubs and young people in parties. The intoxications, above all with alcohol combination, can be severe, with coma and breathing depression, or even fatal. Chronic use leads to psychic and physical dependence; withdrawal syndrome can be severe, with agitation and delirium. In 1999, GHB classification as a narcotic resulted in the increased use of GHB prodrugs gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD), which were easily commercially available as solvent and cleaning products. Like GHB, they have a narrow window of use, and share similar toxicity. Their increased cases of recreational use and of severe drug intoxication, abuse and dependence, led the French Ministry of Health in 2011 to prohibit their sale and transfer to the public.

Source inference of exogenous gamma-hydroxybutyric acid (GHB) administered to humans by means of carbon isotopic ratio analysis: novel perspectives regarding forensic investigation and intelligence issues.

γ-Hydroxybutyric acid (GHB) is an endogenous short-chain fatty acid popular as a recreational drug due to sedative and euphoric effects, but also often implicated in drug-facilitated sexual assaults owing to disinhibition and amnesic properties. Whilst discrimination between endogenous and exogenous GHB as required in intoxication cases may be achieved by the determination of the carbon isotope content, such information has not yet been exploited to answer source inference questions of forensic investigation and intelligence interests. However, potential isotopic fractionation effects occurring through the whole metabolism of GHB may be a major concern in this regard. Thus, urine specimens from six healthy male volunteers who ingested prescription GHB sodium salt, marketed as Xyrem(®), were analysed by means of gas chromatography/combustion/isotope ratio mass spectrometry to assess this particular topic. A very narrow range of δ(13)C values, spreading from -24.81‰ to -25.06‰, was observed, whilst mean δ(13)C value of Xyrem(®) corresponded to -24.99‰. Since urine samples and prescription drug could not be distinguished by means of statistical analysis, carbon isotopic effects and subsequent influence on δ(13)C values through GHB metabolism as a whole could be ruled out. Thus, a link between GHB as a raw matrix and found in a biological fluid may be established, bringing relevant information regarding source inference evaluation. Therefore, this study supports a diversified scope of exploitation for stable isotopes characterized in biological matrices from investigations on intoxication cases to drug intelligence programmes.

Effect of ABCG2 genotypes on the pharmacokinetics of A771726, an active metabolite of prodrug leflunomide, and association of A771726 exposure with serum uric acid level.

OBJECTIVE: It has been reported that leflunomide and its active metabolite, A771726, are substrates of the ABCG2 (BCRP) transporter in vitro. Recent genome-wide association studies have shown that ABCG2 transporter modulates serum uric acid (UA) levels. We explored the role of ABCG2 genotypes in the pharmacokinetics of A771726 and the relationship between serum UA levels and pharmacokinetics of A771726 in healthy participants. METHODS: Twenty-four healthy individuals were recruited and genotyped for ABCG2. After administration of a single dose of 20 mg leflunomide, plasma concentrations of A771726 were measured. Serum UA levels were measured just before medication, and ABCG2 c.421C>A and c.34G> A polymorphism were genotyped. RESULTS: ABCG2 c.421C>A but not c.34G>A substantially influenced the pharmacokinetics of A771726. A771726 C(max) was 30% higher, area under the concentration-time curve (AUC) 83% larger, and oral clearance (CL/F) 41% lower in c.421C>A carriers than in noncarriers. Serum UA levels were also higher in carriers than in noncarriers and exhibited a strong and positive correlation with A771726 AUC (Spearman r = 0.6746, P = 0.0003), but a negative correlation was observed with A771726 CL/F (Spearman r = -0.6616, P = 0.0004). CONCLUSION: ABCG2 c.421C>A but not c.34G>A polymorphism appears to be a major determinant of interindividual variability in A771726 disposition. Additionally, serum UA levels exhibited a strong correlation with exposure to A771726.

γ-Hydroxybutyric Acid: Pharmacokinetics, Pharmacodynamics, and Toxicology.

Gamma-hydroxybutyrate (GHB) is a short-chain fatty acid present endogenously in the brain and used therapeutically for the treatment of narcolepsy, as sodium oxybate, and for alcohol abuse/withdrawal. GHB is better known however as a drug of abuse and is commonly referred to as the "date-rape drug"; current use in popular culture includes recreational "chemsex," due to its properties of euphoria, loss of inhibition, amnesia, and drowsiness. Due to the steep concentration-effect curve for GHB, overdoses occur commonly and symptoms include sedation, respiratory depression, coma, and death. GHB binds to both GHB and GABAB receptors in the brain, with pharmacological/toxicological effects mainly due to GABAB agonist effects. The pharmacokinetics of GHB are complex and include nonlinear absorption, metabolism, tissue uptake, and renal elimination processes. GHB is a substrate for monocarboxylate transporters, including both sodium-dependent transporters (SMCT1, 2; SLC5A8; SLC5A12) and proton-dependent transporters (MCT1-4; SLC16A1, 7, 8, and 3), which represent significant determinants of absorption, renal reabsorption, and brain and tissue uptake. This review will provide current information of the pharmacology, therapeutic effects, and pharmacokinetics/pharmacodynamics of GHB, as well as therapeutic strategies for the treatment of overdoses. Graphical abstract.

Precision Medicine With Leflunomide: Consideration of the DHODH Haplotype and Plasma Teriflunomide Concentration and Modification of Outcomes in Patients With Rheumatoid Arthritis.

OBJECTIVE: Leflunomide is a commonly used disease-modifying drug in the treatment of rheumatoid arthritis (RA). Its effects are mediated via inhibition of dihydroorotate dehydrogenase (DHODH) by its active metabolite teriflunomide, and the pharmacokinetics of teriflunomide are highly variable. Our objective was to examine the association between the DHODH haplotype and plasma teriflunomide concentration with response to leflunomide in patients with RA where leflunomide was added to an existing disease-modifying drug regimen after failure to achieve an adequate response with conventional triple therapy. METHODS: Patients with RA who were taking, or were about to initiate, leflunomide were included. Participant characteristics, including the DHODH haplotype, were determined. Up to 5 plasma samples were collected after leflunomide was initiated for assays of total and free teriflunomide concentration. Disease activity was determined via the 28-joint Disease Activity Score (DAS28). The association between DAS28 scores and patient covariates was determined by linear mixed-effects modeling. RESULTS: A total of 67 patients were included in the study. The DAS28 score after initiation of leflunomide was associated with the baseline DAS28 score (ß = 0.70, P < 0.001) and was higher in those who carried the DHODH haplotype 2 (ß = 0.56. P = 0.01) and did not carry the shared epitope (ß = 0.56, P = 0.013). As total and free plasma teriflunomide concentration increased, the DAS28 score was significantly lower (P < 0.001 and P = 0.001, respectively). When considering threshold concentrations, teriflunomide concentrations >16 mg/liter were associated with a DAS28 score that was 0.33 lower, and when free teriflunomide concentration was >35 µg/liter, the DAS28 score was 0.32 lower. CONCLUSION: Teriflunomide concentration and carriage of the DHODH haplotype 2 are associated with response to leflunomide in patients with RA, and a total plasma teriflunomide concentration of at least 16 mg/liter is needed to maximize the likelihood of response.

Monocarboxylate transporter-mediated transport of gamma-hydroxybutyric acid in human intestinal Caco-2 cells.

The objectives of this study were to determine mRNA expression of monocarboxylate transporters (MCT) and to evaluate intestinal transport of the MCT substrates gamma-hydroxybutyrate (GHB) and d-lactate in human intestinal Caco-2 cells. The presence of mRNA for MCT1, 2, 3, and 4 was observed in Caco-2 cells. The uptake of both GHB and d-lactate in Caco-2 cells was demonstrated to be pH- and concentration-dependent and sodium-independent. The uptake of GHB and d-lactate was best described by a Michaelis-Menten equation with passive diffusion (GHB: K(m) = 17.6 +/- 10.5 mM, V(max) = 17.3 +/- 11.7 nmol/min/mg, and P = 0.38 +/- 0.15 microl/min/mg; and d-lactate: K(m) = 6.0 +/- 2.9 mM, V(max) = 35.0 +/- 18.4 nmol/min/mg, and P = 1.3 +/- 0.6 microl/min/mg). The uptake of GHB and d-lactate was significantly decreased by the known MCT inhibitor alpha-cyano-4-hydroxycinnamate and the MCT substrates GHB and d-lactate but not by the organic cation tetraethylammonium chloride. Directional flux studies with both GHB and d-lactate suggested the involvement of carrier-mediated transport with the permeability in the apical to basolateral direction higher than that in the basolateral to apical direction. These findings confirm the presence of MCT1-4 in Caco-2 cells and demonstrate GHB and d-lactate transport characteristics consistent with proton-dependent MCT-mediated transport.

Investigation of the influence of CYP1A2 and CYP2C19 genetic polymorphism on 2-Cyano-3-hydroxy-N-[4-(trifluoromethyl)phenyl]-2-butenamide (A77 1726) pharmacokinetics in leflunomide-treated patients with rheumatoid arthritis.

Leflunomide is a disease-modifying antirheumatic drug used for the treatment of rheumatoid arthritis (RA). Cytochromes P450, mainly CYP1A2 and CYP2C19, may be involved in the transformation of leflunomide to leflunomide metabolite (A77 1726, 2-cyano-3-hydroxy-N-[4-(trifluoromethyl)phenyl]-2-butenamide). The aim of this study was to investigate whether genetic polymorphisms in CYP1A2 and CYP2C19 influence leflunomide pharmacokinetics, treatment response, and the occurrence of adverse drug reactions (ADRs). The study included 67 patients with RA and 4 patients with polyarthritis resembling RA and psoriasis treated with leflunomide. A77 1726 steady-state plasma concentrations were determined by validated high-performance liquid chromatography with UV detection. A population pharmacokinetic model was developed to estimate the oral clearance (CL/F) and volume of distribution (V/F). A genotyping approach was used to determine C-163A, C-729T, and T-739G in the CYP1A2 gene as well as single nucleotide polymorphisms that characterize CYP2C19*2, *3, *4, and *17 alleles. A large interindividual variability in trough A77 1726 steady-state plasma concentrations was observed (from 1.9 to 156.9 mg/l). A77 1726 CL/F was 71% higher in carriers of the CYP2C19*2 allele compared with noncarriers. The A77 1726 average steady-state plasma concentration was associated with the treatment response. Patients with a greater decrease in C-reactive protein (CRP) had higher average steady-state plasma A77 1726 concentrations: 49.7 +/- 39.0 mg/l in patients with DeltaCRP of more than 8.5 mg/l compared with 24.8 +/- 13.7 mg/l in patients with DeltaCRP of

Blood and urine analyses after radioembolization of liver malignancies with [166Ho]Ho-acetylacetonate-poly(l-lactic acid) microspheres.

BACKGROUND: [166Ho]Ho-acetylacetonate-poly(L-lactic acid) microspheres were used in radioembolization of liver malignancies by intra-arterial administration. The primary aim of this study was to assess the stability and biodistribution of these microspheres. MATERIALS AND METHODS: Peripheral blood and urine samples were obtained from two clinical studies. Patient and in vitro experiment samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), gamma-ray spectroscopy, light microscopy, Coulter particle counting, and high performance liquid chromatography (HPLC). RESULTS: The median percentage holmium compared to the total amount injected into the hepatic artery was 0.19% (range 0.08-2.8%) and 0.32% (range 0.03-1.8%) in the 1 h blood plasma and 24 h urine, respectively. Both the blood plasma and urine were correlated with the neutron irradiation exposure required for [166Ho]Ho-AcAc-PLLA microsphere production (ρ = 0.616, p = 0.002). After a temporary interruption of the phase 2 clinical study, the resuspension medium was replaced to precipitate [166Ho]Ho3+ pre-administration using phosphate. The in vitro near-maximum neutron irradiation experiments showed significant [166Ho]Ho-AcAc-PLLA microsphere damage. CONCLUSION: The amount of holmium in the peripheral blood and urine samples after [166Ho]Ho-AcAc-PLLA microsphere intrahepatic infusion was low. A further decrease was observed after reformulation of the resuspension solution but minimization of production damage is necessary.

Intoxications due to ingestion of gamma-butyrolactone: organ distribution of gamma-hydroxybutyric acid and gamma-butyrolactone.

In Europe, the misuse of gamma-hydroxybutyric acid (GHB) and its analogues has increased within the recent years. Here, 2 fatalities and 1 nonfatal intoxication resulting from ingestion of gamma-butyrolactone (GBL), a precursor of GHB, are presented. GHB was quantified involving the conversion to GBL by application of a gas chromatography-mass spectrometry (GC/MS) method. Besides quantitation of GHB equivalents ("total GBL"), all specimens of case 1 were analyzed for the metabolic precursor GBL itself (absolute GBL). The cause of death in each case was attributed to GHB intoxication; the manner of death was suicide in the first case and accidental in the second one. Another yet nonfatal GHB intoxication was reported by an emergency department concerning a 36-year-old woman who was hospitalized due to her comatose state and loss of adverse effects reflexes. Here nail polish remover pads were used as source for GBL.