Observational infant exploratory [(14)C]-paracetamol pharmacokinetic microdose/therapeutic dose study with accelerator mass spectrometry bioanalysis.

AIMS: The aims of the study were to compare [(14)C]-paracetamol ([(14)C]-PARA) paediatric pharmacokinetics (PK) after administration mixed in a therapeutic dose or an isolated microdose and to develop further and validate accelerator mass spectrometry (AMS) bioanalysis in the 0-2 year old age group. METHODS: [(14)C]-PARA concentrations in 10-15 µl plasma samples were measured after enteral or i.v. administration of a single [(14)C]-PARA microdose or mixed in with therapeutic dose in infants receiving PARA as part of their therapeutic regimen. RESULTS: Thirty-four infants were included in the PARA PK analysis for this study: oral microdose (n = 4), i.v. microdose (n = 6), oral therapeutic (n = 6) and i.v. therapeutic (n = 18). The respective mean clearance (CL) values (SDs in parentheses) for these dosed groups were 1.46 (1.00) l h(-1), 1.76 (1.07) l h(-1), 2.93 (2.08) l h(-1) and 2.72 (3.10) l h(-1), t(1/2) values 2.65 h, 2.55 h, 8.36 h and 7.16 h and dose normalized AUC(0-t) (mg l(-1) h) values were 0.90 (0.43), 0.84 (0.57), 0.7 (0.79) and 0.54 (0.26). CONCLUSIONS: All necessary ethical, scientific, clinical and regulatory procedures were put in place to conduct PK studies using enteral and systemic microdosing in two European centres. The pharmacokinetics of a therapeutic dose (mg kg(-1)) and a microdose (ng kg(-1)) in babies between 35 to 127 weeks post-menstrual age. [(14)C]-PARA pharmacokinetic parameters were within a two-fold range after a therapeutic dose or a microdose. Exploratory studies using doses significantly less than therapeutic doses may offer ethical and safety advantages with increased bionalytical sensitivity in selected exploratory paediatric pharmacokinetic studies.

Deviations from classical droplet evaporation theory.

In this article, we show that significant deviations from the classical quasi-steady models of droplet evaporation can arise solely due to transient effects in the gas phase. The problem of fully transient evaporation of a single droplet in an infinite atmosphere is solved in a generalized, dimensionless framework with explicitly stated assumptions. The differences between the classical quasi-steady and fully transient models are quantified for a wide range of the 10-dimensional input domain and a robust predictive tool to rapidly quantify this difference is reported. In extreme cases, the classical quasi-steady model can overpredict the droplet lifetime by 80%. This overprediction increases when the energy required to bring the droplet into equilibrium with its environment becomes small compared with the energy required to cool the space around the droplet and therefore establish the quasi-steady temperature field. In the general case, it is shown that two transient regimes emerge when a droplet is suddenly immersed into an atmosphere. Initially, the droplet vaporizes faster than classical models predict since the surrounding gas takes time to cool and to saturate with vapour. Towards the end of its life, the droplet vaporizes slower than expected since the region of cold vapour established in the early stages of evaporation remains and insulates the droplet.

Diarrhoea Management using Over-the-counter Nutraceuticals in Daily practice (DIAMOND): a feasibility RCT on alternative therapy to reduce antibiotic use.

BACKGROUND: Although rarely indicated, antibiotics are commonly used for acute diarrhoea in China. We conducted a randomised, double blind exploratory clinical trial of loperamide, berberine and turmeric for treatment of acute diarrhoea. METHODS: Adults with acute uncomplicated diarrhoea aged 18 to 70 were randomised to 4 groups: (A) loperamide; (B) loperamide and berberine; (C) loperamide and turmeric; (D) loperamide, berberine and turmeric. All participants were given rescue ciprofloxacin for use after 48 h if symptoms worsened or were unimproved. Primary endpoints were feasibility and ciprofloxacin use during the 2-week follow-up period. Semi-structured interviews were conducted following recruitment and were analysed thematically. Recruiting doctors, delivery pharmacists and research assistants were blinded to treatment allocation. RESULTS: Only 21.5% (278/1295) of patients screened were deemed eligible, and 49% (136/278) of these consented and were entered into the final analysis. Most participants had mild symptoms, because most patients with moderate or severe symptoms wanted to be given antibiotics. Follow-up was good (94% at 2 weeks). Only three participants used rescue antibiotics compared to 67% of acute diarrhoea patients in the hospital during the recruitment period. The median symptom duration was 14 h in group B (interquartile range (IQR) 10-22), 16 h in group D (IQR 10-22), 18 h in group A (IQR 10-33) and 20 h in group C (IQR 16-54). Re-consultation rates were low. There were no serious treatment-related adverse events. Most interviewed participants said that although they had believed antibiotics to be effective for diarrhoea, they were surprised by their quick recovery without antibiotics in this trial. CONCLUSION: Although recruitment was challenging because of widespread expectations for antibiotics, patients with mild diarrhoea accepted trying an alternative. The three nutraceuticals therapy require further evaluation in a fully powered, randomised controlled trial among a broader sample. TRIAL REGISTRATION: ChiCTR-IPR-17014107.

Thermal conductivity and molecular heat transport of nanofluids.

Fluid media such as water and ethylene glycol are usually quite poor conductors of heat. Nanoparticles can improve the thermal properties of fluids in a remarkable manner. Despite a plethora of experimental and theoretical studies, the underlying physics of heat transport in nanofluids is not yet well understood. Furthermore, the link between nanoscale energy transport and bulk properties of nanofluids is not fully established. This paper presents a thermal conductivity model, encapsulating solid-liquid interfacial thermal resistance, particle shape factor and the variation of thermal conductivity across a physisorbed fluidic layer on a nanoparticle surface. The developed model for thermal conductivity integrates the interfacial Kapitza resistance, the characteristics of a nanolayer, convective diffusion and surface energy with capillary condensation. In addition, the thickness of the nanolayer is predicted using the Brunauer-Emmett-Teller (BET) isotherms and micro/nano-menisci generated pressures of condensation. Such a comprehensive model for thermal conductivity of nanoparticles and systematic study has not hitherto been reported in the literature. The thermal conductivity model is evaluated using experimental data available in open literature.

Pharmacokinetic investigation of imatinib using accelerator mass spectrometry in patients with chronic myeloid leukemia.

PURPOSE: To investigate the potential use of accelerator mass spectrometry (AMS) in the study of the clinical pharmacology of imatinib. EXPERIMENTAL DESIGN: Six patients who were receiving imatinib (400 mg/d) as part of their ongoing treatment for chronic myeloid leukemia (CML) received a dose containing a trace quantity (13.6 kBq) of (14)C-imatinib. Blood samples were collected from patients before and at various times up to 72 h after administration of the test dose and were processed to provide samples of plasma and peripheral blood lymphocytes (PBL). Samples were analyzed by AMS, with chromatographic separation of parent compound from metabolites. In addition, plasma samples were analyzed by liquid chromatography/mass spectrometry (LCMS). RESULTS: Analysis of the AMS data indicated that imatinib was rapidly absorbed and could be detected in plasma up to 72 h after administration. Imatinib was also detectable in PBL at 24 h after administration of the (14)C-labeled dose. Comparison of plasma concentrations determined by AMS with those derived by LCMS analysis gave similar average estimates of area under plasma concentration time curve (26 +/- 3 versus 27 +/- 11 microg/mL.h), but with some variation within each individual. CONCLUSIONS: Using this technique, data were obtained in a small number of patients on the pharmacokinetics of a single dose of imatinib in the context of chronic dosing, which could shed light on possible pharmacologic causes of resistance to imatinib in CML.

Comparison of accelerator mass spectrometry with gas chromatography for the determination of pesticide residues in individual items in the diets of wild birds and mammals.

Methods to refine the assessment of exposure of wild birds and mammals to pesticides required measurement of pesticide residues in very small samples of their diets. Sample sizes were in the 1-100 mg range, and the target residue for measurement was 0.01 mg/kg. Gas chromatography-mass spectrometry (GC-MS) with large volume injection was compared with the use of an accelerator mass spectrometer (AMS) to measure residues of pesticide labeled at near-background levels with carbon-14. The GC-MS method was able to detect residues down to 0.1 ng per item of diet, and the AMS detected the radiolabel down to 1 mBq (0.06 disintegration per minute, 1 ng of pesticide at the specific activity used) per sample. The target residue level was achieved by the GC-MS method for samples down to 10 mg. The GC method appeared to be best suited to monitoring residues in field studies, and the AMS shows great potential for use in laboratory experiments concerning pesticide degradation.

AFN-1252 in vitro absorption studies and pharmacokinetics following microdosing in healthy subjects.

OBJECTIVES: To investigate the absorption, distribution, metabolism and excretion of AFN-1252, a novel inhibitor of the essential FabI enzyme in Staphylococcus spp., in vitro and following microdosing in healthy adult male subjects following intravenous and oral administration. METHODS: Three ADME studies, comprising a Caco-2 assay, a rat intestinal perfusion model and a microdosing study in healthy human volunteers, were conducted. RESULTS: The Caco-2 assay indicated that AFN-1252 in solution is well-absorbed and undergoes insignificant efflux, and its transport across the intestinal wall is probably passive. In the rat intestinal perfusion model, AFN-1252 exhibited high permeability potential across three segments, in the rank order of jejunum=ileum>colon. Taken together with the low aqueous solubility, the data from these studies indicate that AFN-1252 is a BCS Class II molecule with solubility-limited absorption. Analysis of the [(14)C]-AFN-1252 radioactivity concentration-time data indicated similar pharmacokinetics following intravenous and oral administration in the microdosing study in healthy volunteers. These included long terminal half-lives of ∼7 h and 83% bioavailability, indicating that there was little first-pass metabolism following oral dosing. AFN-1252 exhibited good distribution to skin and skin structures where its anti-staphylococcal activity may be required. Urinary and faecal excretion are major elimination routes for [(14)C]-AFN-1252 following intravenous or oral administration. CONCLUSIONS: AFN-1252 has the potential for both intravenous and oral administration, once- or twice-daily dosing and good tissue distribution in humans. Further safety, efficacy and pharmacokinetic studies in man are required to investigate therapeutically-relevant doses for this novel agent and its targeted selectivity and high potency against Staphylococcus spp.

Comparative pharmacokinetics between a microdose and therapeutic dose for clarithromycin, sumatriptan, propafenone, paracetamol (acetaminophen), and phenobarbital in human volunteers.

A clinical study was conducted to assess the ability of a microdose (100 µg) to predict the human pharmacokinetics (PK) following a therapeutic dose of clarithromycin, sumatriptan, propafenone, paracetamol (acetaminophen) and phenobarbital, both within the study and by reference to the existing literature on these compounds and to explore the source of any nonlinearity if seen. For each drug, 6 healthy male volunteers were dosed with 100 µg (14)C-labelled compound. For clarithromycin, sumatriptan, and propafenone this labelled dose was administered alone, i.e. as a microdose, orally and intravenously (iv) and as an iv tracer dose concomitantly with an oral non-labelled therapeutic dose, in a 3-way cross over design. The oral therapeutic doses were 250, 50, and 150 mg, respectively. Paracetamol was given as the labelled microdose orally and iv using a 2-way cross over design, whereas phenobarbital was given only as the microdose orally. Plasma concentrations of total (14)C and parent drug were measured using accelerator mass spectrometry (AMS) or HPLC followed by AMS. Plasma concentrations following non-(14)C-labelled oral therapeutic doses were measured using either HPLC-electrochemical detection (clarithromycin) or HPLC-UV (sumatriptan, propafenone). For all five drugs an oral microdose predicted reasonably well the PK, including the shape of the plasma profile, following an oral therapeutic dose. For clarithromycin, sumatriptan, and propafenone, one parameter, oral bioavailability, was marginally outside of the normally acceptable 2-fold prediction interval around the mean therapeutic dose value. For clarithromycin, sumatriptan and propafenone, data obtained from an oral and iv microdose were compared within the same cohort of subjects used in the study, as well as those reported in the literature. For paracetamol (oral and iv) and phenobarbital (oral), microdose data were compared with those reported in the literature only. Where 100 µg iv (14)C-doses were given alone and with an oral non-labelled therapeutic dose, excellent accord between the PK parameters was observed indicating that the disposition kinetics of the drugs tested were unaffected by the presence of therapeutic concentrations. This observation implies that any deviation from linearity following the oral therapeutic doses occurs during the absorption process.

Pharmacokinetics of fexofenadine: evaluation of a microdose and assessment of absolute oral bioavailability.

A human pharmacokinetic study was performed to assess the ability of a microdose to predict the pharmacokinetics of a therapeutic dose of fexofenadine and to determine its absolute oral bioavailability. Fexofenadine was chosen to represent an unmetabolized transporter substrate (P-gP and OATP). Fexofenadine was administered to 6 healthy male volunteers in a three way cross-over design. A microdose (100microg) of (14)C-drug was administered orally (period 1) and intravenously by 30min infusion (period 2). In period 3 an intravenous tracer dose (100microg) of (14)C-drug was administered simultaneously with an oral unlabelled therapeutic dose (120mg). Plasma was collected from all 3 periods and analysed for both total (14)C content and parent drug by accelerator mass spectrometry (AMS). For period 3, plasma samples were also analysed using HPLC-fluorescence to determine total drug concentration. Urine was collected and analysed for total (14)C. Good concordance between the microdose and therapeutic dose pharmacokinetics was observed. Microdose: CL 13L/h, CL(R) 4.1L/h, V(ss) 54L, t(1/2) 16h; therapeutic dose: CL 16L/h, CL(R) 6.2L/h, V(ss) 64L, t(1/2) 12h. The absolute oral bioavailability of fexofenadine was 0.35 (microdose 0.41, therapeutic dose 0.30). Despite a 1200-fold difference in dose of fexofenadine, the microdose predicted well the pharmacokinetic parameters following a therapeutic dose for this transporter dependent compound.