Nutrimetric Validation of Solanidine as Dietary-Derived CYP2D6 Activity Marker In Vivo.

CYP2D6 is involved in the metabolism of many drugs. Its activity is affected by pharmacogenetic variability leading to highly polymorphic phenotypes between individuals, affecting safety and efficacy of drugs. Recently, solanidine, a steroidal alkaloid from potatoes, and its metabolites, has been identified as a dietary-derived activity marker for CYP2D6. The intraday variability in plasma within individuals has not been studied yet in healthy subjects. As part of a CYP phenotyping cocktail study with 20 healthy participants, plasma concentrations of solanidine, 4-OH-solanidine and 3,4-secosolanidine-3,4-dioic acid (SSDA) were determined using a sensitive liquid chromatography-mass spectrometry method in urine and in plasma at timepoints 0, 2.5, 5, 8, and 24 hours after intake of test substances. The participants were phenotyped for CYP2D6 with oral metoprolol (12.5 mg) with 15 plasma sampling points over 24 hours (DRKS00028922). Metabolic ratios (MRs) of metabolite to parent plasma concentrations were formed from single timepoints and the area under the curve (AUC). All participants were genotyped for CYP2D6. The intra-individual variability of the CYP2D6 metabolite SSDA was highly stable with a median SD of 11.62% over 24 hours. MR SSDA/solanidine was more variable (median SD 31.90%) but correlated significantly at all measured timepoints with AUC MR α-OH-metoprolol/metoprolol. The AUC MR SSDA/solanidine showed a significant linear relationship with the genetically predicted CYP2D6 activity score. This study substantiates the MR SSDA/solanidine as CYP2D6 activity marker. The high correlation with metoprolol MR indicates a valid prediction of the CYP2D6 phenotype at any timepoint during the study day.

Ten years after: findings from the medical surveillance program on Health Effects in High-Level Exposure to PCB (HELPcB).

After the detection of high environmental and occupational exposure to polychlorinated biphenyls (PCBs) in a German recycling company for transformers and capacitors in 2010, the multidisciplinary medical surveillance program "HELPcB" (Health Effects in High-Level Exposure to PCB) was established for former PCB-exposed workers of the company, their family members, employees of surrounding companies, and area residents to investigate potential adverse health effects by PCB exposure in a longitudinal study approach with up to seven examination time points between 2010 and 2019. More than 300 individuals were enrolled into the program. Assessments particularly included plasma and urine concentrations of PCB congeners and their metabolites, clinical laboratory parameters, Comet assay, analysis of telomere length, neuropsychological examinations, psychological screening, abdominal and thyroid ultrasound examination. This review summarizes the main results of the studies conducted in the HELPcB program yielding relevant new data on potential adverse effects of PCB exposure in humans and potential mechanisms that underlie these effects. Even larger studies in PCB-exposed individuals are warranted to confirm the results of this program and to further establish causality between PCB exposure and clinical effects in humans.

Multiple Dose Pharmacokinetics of Tapentadol Oral Solution for the Treatment of Moderate to Severe Acute Pain in Children Aged 2 to <7 Years.

Background: This prospective, open-label trial was conducted to fulfil a post-approval commitment made to the competent authorities to extend the indication of the strong opioid analgesic tapentadol hydrochloride oral solution (OS) to the pediatric population. Patients and Methods: The trial assessed the pharmacokinetic (PK) profile of tapentadol, tapentadol-O-glucuronide and tapentadol-O-sulfate after administration of multiple doses of tapentadol OS (1.25 mg tapentadol/kg bodyweight every 4 h for up to 72 h) in children aged 2 to <7 years after a painful event that produces acute pain requiring treatment with a strong analgesic. The obtained PK data were integrated into a previously developed population PK (popPK) model based on single-dose data and then a model-based PK evaluation was performed. The primary trial endpoint was the area under the concentration-time curve at steady state for the dosing interval (AUCτ,ss) for tapentadol. Results: Ten children received tapentadol OS; all completed the trial. Multiple administrations of the trial medication resulted in tapentadol serum concentrations within the concentration range predicted by the previously developed popPK model. The estimated model-based AUCτ,ss values for tapentadol ranged from 142 to 321 h•ng/mL. They were within the predicted exposure range with no higher than expected accumulation for the employed dosing regimen and also within the targeted steady state exposure range observed in adults receiving multiple doses of immediate release tapentadol 50 to 100 mg. The treatment regimen was safe and well tolerated. Conclusion: The findings confirm the linear and predictable PK profile of tapentadol hydrochloride. The good agreement between the observed data and the model predictions shows the value of modelling and simulations in the planning and analysis of pediatric clinical trials and the ability to utilize the established PK models to predict multiple dose exposure.

Influence on study outcomes of an inpatient study by the behavior of the study staff (PINgPOng): study protocol for a randomized clinical trial.

BACKGROUND: The placebo effect as the symptom improvement following inert treatments is a fixed component of RCTs to differentiate between specific effects of the tested pharmacological substance from other unspecific effects. The PINgPOng study was set up to analyze the influence of a study team trained to either minimize the placebo response and optimize drug-placebo differences or to maximize the placebo response to increase drug efficacy by unspecific factors on the study results of a RCT in a classical early clinical trial setting. METHODS/DESIGN: PINgPOng is a single-center, prospective, randomized, double-blind, placebo-controlled study in a 3-group, 2-sequence, 2-period cross-over design. The study is conducted according to the principles of ICH-GCP and the Declaration of Helsinki on the Phase I-Unit of the University Hospital Bonn. The primary endpoint is the pain intensity in the cold pressor test before and after the administration of 15 mg oxycodone or placebo. The pain intensity is compared between three study conditions: 32 healthy volunteers in each study arm will be treated either by an untrained study team (arm A), by a study team trained to maximize (arm B), or to minimize placebo responses (arm C). Neuroendocrine factors (alpha-amylase activity, salivary cortisol), characteristic traits (anxiety, depression, stress), and somatic reactions are analyzed as covariates of the pain perception. DISCUSSION: The PINgPOng study will allow to answer the question whether and to what extent the behavior of a trained study team (neutral vs. maximize vs. minimize placebo responses) will differentially affect placebo responses in a setting of a highly standardized early clinical trial. The results will help to control the placebo effects by education of the clinical study team and to avoid unnecessary high placebo effects in clinical development. TRIAL REGISTRATION: German Clinical Trials Register DRKS00013586 . Registered on December 22, 2017.

How to Interpret an Investigator's Brochure for Meaningful Risk Assessment: Results of an AGAH Discussion Forum.

PURPOSE: A discussion forum was hosted by the Association for Applied Human Pharmacology (AGAH e.V.) to critically debate how to interpret and optimise the Investigator's Brochure (IB) for meaningful risk assessment of early clinical trials. MATERIALS AND METHODS: Four topics were specifically discussed: deficiencies/uncertainties in IBs, guidance for the investigator, reference safety information, and potential risks for human subjects associated with inadequate non-clinical safety assessment in the IB. In each case, 43 participants took part in a real-time online survey with pre-defined questions to capture the audience's opinion. RESULTS: The 'Summary of Data and Guidance for the Investigator' was considered as the section of the IB with the highest need for improvement with emphasis on readability, comprehensibility, timeliness of data, and appropriateness for risk assessment. It was suggested that the IB should at least be signed by the sponsor's scientist responsible for the content on pharmacology and toxicology. It was agreed that sponsors should consider thoroughly whether changes to an IB constitute a substantial amendment, and that the IB should include a section on the change history. Non-clinical pharmacology studies with negative outcomes should be reported in the IB in order to avoid assessment bias. The reference safety information for expectedness assessment of suspected serious adverse reactions should be provided as a stand-alone section of the IB. CONCLUSION: The overall consensus was that an optimised presentation of data will ensure the best possible understanding of a compound's characteristics and an optimal benefit-risk assessment which will safeguard the participants in clinical trials.

Oxycodone Effect on Pupil Constriction in Recreational Opioid Users: A Pharmacokinetic/Pharmacodynamic Meta-Analysis Approach.

INTRODUCTION: Understanding the effect of oxycodone pharmacokinetics (PK) on µ-opioid receptor binding benefits from an integrated approach to compiling the results of multiple studies. The current pharmacokinetic/pharmacodynamic (PK/PD) model analysis brings together various studies to support the interpretation of newly collected PK/PD data, putting the new results into the perspective of the full concentration-effect curve. METHODS: A two-step modeling approach was applied to characterize the PK of oxycodone and its PK/PD relationship for the pupil diameter as a biomarker for µ-opioid receptor binding in recreational opioid users. First, a model-based meta-analysis (MBMA) was used to quantify the state-of-the-art knowledge from seven published studies, each of which contained part of the data needed for full characterization. Subsequently, the estimated parameters with uncertainty from the MBMA were used as prior information for a model developed on newly collected clinical data after intranasal administration in a clinical abuse potential trial. RESULTS: The inclusion of intravenous data in the MBMA showed that the PK of oxycodone can be described by a two-compartmental model, and allowed for the estimation of absolute bioavailability after intranasal and oral administration. A hysteresis loop was observed when plotting plasma concentrations and pupil constriction, which was approximated using an effect compartment. The totality of literature data enabled the identification of a Hill equation for the drug effect. The model with prior information fitted successfully to the newly collected data, where most parameter estimates had their confidence intervals overlapping with the prior distribution. The new data led to a slightly lower intranasal absorption rate constant, explaining the longer apparent half-life of oxycodone in the newly collected data. The PK/PD model parameters were confirmed by the new data, leading to the following estimates: half maximal inhibitory concentration (IC50) of 26.5 ng/mL, maximum pupil restriction of 66.0% from baseline, and a Hill factor of 1.05. CONCLUSIONS: The new data confirmed the PK profile and the PK/PD relationship identified using the MBMA, resulting in similar parameter estimates except for the intranasal absorption rate constant. The latter was lower than in the MBMA and explained the slightly longer apparent half-life of oxycodone in the newly collected data.

Evaluation of the effect of naltrexone coadministration on the pharmacokinetics of oxycodone in a randomized phase 1 clinical trial
.

OBJECTIVE: Oxycodone is a centrally acting µ-opioid agonist used as a strong analgesic. The opioid receptor antagonist -naltrexone is often coadministered to healthy subjects in clinical trials evaluating the pharmacokinetics (PK) of oxycodone to minimize its pharmacodynamic opioid effects. One objective of this relative bioavailability trial in healthy subjects was to investigate the effect of naltrexone on the PK of oxycodone. MATERIALS AND METHODS: A randomized, single-dose, parallel-group, within-groups crossover, clinical trial was conducted in 24 healthy subjects. 12 subjects were to receive a new oxycodone prolonged-release (PR) tablet (test) with naltrexone (T+) and without naltrexone (T) in the fasted state. Additionally, 12 subjects were to receive an Oxygesic PR tablet (reference) with naltrexone (R+) and without naltrexone (R) in the fasted state. Naltrexone was given orally 1.5 hours prior to each oxycodone administration. Pharmacokinetics, safety, and tolerability were assessed. RESULTS: The PK parameters of either oxycodone formulation were not changed with naltrexone administration under fasted conditions (point estimate T+/T (corresponding 90% confidence interval): Cmax: 103% (88 - 119%), AUC0-t: 97% (87 - 108%), AUC: 97% (88 - 108%); point estimate R+/R (corresponding 90% confidence interval): Cmax: 104% (97 - 112%), AUC0-t: 95% (88 - 102%), AUC: 94% (87 - 100%)). The safety and tolerability of both formulations was not qualitatively affected by naltrexone coadministration; however, treatment with naltrexone coadministration showed lower frequencies of adverse events. CONCLUSION: Oral naltrexone does not affect the PK of oral oxycodone under fasted conditions. A naltrexone block can be applied in oxycodone PK trials to minimize adverse opioid effects.

Effect of combined sublethal X-ray irradiation and cyclosporine A treatment in NOD scid gamma (NSG) mice.

Cyclosporine A (CsA) is used in hematopoietic stem cell transplantations (HSCT) to prevent graft-versus-host disease (GvHD). GvHD is the most severe side effect of allogeneic HSCT and efficient therapies are lacking. Mouse models are an essential tool for assessing potential new therapeutic strategies. Our aim is to mimic a clinical setting as close as possible using CsA treatment after sublethal irradiation in NSG mice and thereby evaluate the feasibility of this mouse model for GvHD studies. The effect of CsA (7.5 mg/kg body weight) on sublethally X-ray irradiated (2 Gy) and non-irradiated NSG mice was tested. CsA was administered orally every twelve hours for nine days. Animals irradiated and treated with CsA showed a shorter survival (n=3/10) than irradiated animals treated with NaCl (n=10/10). Furthermore, combined therapy resulted in severe weight loss (82 ± 6% of initial weight, n=7, day 8), with weight recovery after the CsA application was ceased. A high number of apoptotic events in the liver was observed in these mice (0.431 ± 0.371 apoptotic cells/cm2, n=2, compared to 0.027 ± 0.034 apoptotic cells/cm2, n=5, in the non-irradiated group). Other adverse effects, including a decrease in white blood cell counts were non-CsA-specific manifestations of irradiation. The combination of CsA treatment with irradiation has a hepatotoxic and lethal effect on NSG mice, whereas the treatment without irradiation is tolerated. Therefore, when using in vivo models of GvHD in NSG mice, a combined treatment with CsA and X-ray irradiation should be avoided or carefully evaluated.

Who is a 'healthy subject'?-consensus results on pivotal eligibility criteria for clinical trials.

INTRODUCTION/METHODS: A discussion forum was hosted by the German not-for-profit Association for Applied Human Pharmacology (AGAH e.V.) to critically review key eligibility criteria and stopping rules for clinical trials with healthy subjects, enrolling stakeholders from the pharmaceutical industry, contract research organisations, academia, ethics committees and competent authority. RESULTS: Pivotal eligibility criteria were defined for trials with new investigational medicinal products (IMPs) or with clinically established IMPs. In general, a pulse rate ranging between 50 and 90 beats/min is recommended for first-in-human (FIH) trials, while wider ranges seem acceptable for trials with clinically established IMPs, provided there are no indications of thyroid dysfunction. Hepatic laboratory parameters not to exceed the upper limit of normal (ULN) comprise ALT (alanine aminotransferase) and AST (aspartate aminotransferase) in FIH trials, whereas slight elevations (10% above ULN) seem acceptable in trials with clinically established IMPs without known hepatotoxicity. A normal renal function is required for any clinical trial in healthy subjects. A risk-adapted approach for stopping rules was adopted. Stopping rules for an individual subject are one adverse event of severe intensity or one serious adverse event. In case of a severe adverse event, some stakeholders demand a causal relationship with the IMP (i.e. an adverse reaction). Stopping rules for a cohort are one serious adverse reaction or ≥50% of subjects experiencing any adverse reaction of moderate or severe intensity. CONSEQUENCES: The application of this consensus resulted in a reduction in protocol deficiencies issued by the competent authority.

Population pharmacokinetic/pharmacodynamic modelling of the effects of axomadol and its O-demethyl metabolite on pupil diameter and nociception in healthy subjects.

AIM: The aim of the present study was to characterize the pharmacokinetic/pharmacodynamic (PK/PD) properties of the active components of axomadol and to quantify their contribution to observed the pupillometric and analgesic (measured through the cold pressor test) effects linking the PD engagement biomarker with clinical response. METHODS: Healthy subjects (n = 74) received either placebo or axomadol orally at doses ranging from 66 mg to 225 mg following multiple dosing regimens in two separate clinical trials. Plasma concentrations of the two enantiomers of axomadol and their metabolites, and PD responses were measured at specific times. The population analysis was performed using NONMEM 7.2. RESULTS: The kinetics of the parent drug and its metabolite could be described simultaneously using an extra compartment mimicking the liver, where the metabolite is formed. The SS parent compound elicited a plasma concentration-dependent increase in pupil diameter, with estimates (percentage relative standard errors) of maximal effect (Emax ) and plasma concentration exerting a half-maximal effect (C50 ) of 0.79 (17.4) mm, and 90.7 (27) ng ml(-1) , respectively. The predicted effect site concentrations of the RR O-demethyl metabolite decreased the pupil diameter linearly, with an estimate of the slope of 0.00967 (18.7) mm·ml ng(-1) . An additive model, integrating the net effect on pupil diameter, described adequately the reduction in pain with a linear function. The PK/PD model revealed that each 0.5 mm change in pupil diameter is associated with a 10% decrease in cold pressor area under the concentration-time curve effects. CONCLUSIONS: The PK/PD analysis performed enabled the individual contributions of the active compounds to the observed effects to be identified and quantified. These effects were in accordance with the known mechanisms of action - namely, opioid agonism and noradrenaline reuptake inhibition.

Comparative pharmacokinetics and bioavailability of tapentadol following oral administration of immediate- and prolonged-release formulations.

OBJECTIVE: To evaluate the bioavailability and pharmacokinetics of orally administered tapentadol immediate release (IR) compared with tapentadol prolonged release (PR). METHODS: Three randomized, open-label, crossover studies were conducted in subjects under fasted conditions. Studies 1 and 2 determined the absolute bioavailability and pharmacokinetics of oral tapentadol IR 86 mg and tapentadol PR 86 mg, respectively, relative to a 34-mg intravenous (IV) dose of tapentadol. Study 3 determined the relative bioavailability of tapentadol PR 86 mg vs. tapentadol IR 86 mg. Pharmacokinetic parameters were calculated using non-compartmental analysis and relative bioavailability using dose-adjusted, log-transformed analysis of variance models for maximum concentration (Cmax) and areas under the serum concentration-time curve (AUC0-t and AUC). Adverse events (AEs), vital signs, 12-lead electrocardiograms (ECGs), and laboratory parameters were assessed. RESULTS: Absolute bioavailability was estimated to be 32% (95% confidence interval (CI), 29.4 - 34.8%; n = 24) for tapentadol IR 86 mg and 32% (95% CI, 28.0 - 35.9%; n = 18) for tapentadol PR 86 mg. Based on AUC, the relative bioavailability of tapentadol PR vs. tapentadol IR was 96% (90% CI, 87.8 - 104.4%; n = 16). Following IV administration, tapentadol had an elimination half-life of about 4 hours; in Studies 1 and 2, respectively, mean tapentadol volumes of distribution were 540 and 471 l, and mean clearance was 1,531 and 1,603 ml/min. Compared to tapentadol IR 86 mg, the prolonged-release characteristics of tapentadol PR 86 mg were evident with a lower Cmax (22.5 ng/ml vs. 64.2 ng/ml), a longer time to Cmax (5.0 h vs. 1.5 h), a higher half-value duration (HVD: 12.5 h vs. 3.6 h), and a longer mean residence time (MRT: 10.6 h vs. 6.0 h). The most common AEs reported were dizziness, headache, fatigue, nausea, somnolence, and dry mouth; most AEs were mild. No clinically relevant changes in vital signs, ECG parameters, or laboratory values were observed. CONCLUSIONS: Absolute bioavailability for both tapentadol IR and tapentadol PR was ~ 32% under fasted conditions. Extent of exposure (AUC) for tapentadol PR was very similar to tapentadol IR, whereas Cmax was lower and HVD/MRT longer for the prolonged-release formulation. Overall, the pharmacokinetic characteristics of tapentadol PR enable a twice-daily dosing regimen to be used; such a regimen is expected to improve patient compliance during chronic use.

Effects of acetaminophen, naproxen, and acetylsalicylic acid on tapentadol pharmacokinetics: results of two randomized, open-label, crossover, drug-drug interaction studies.

STUDY OBJECTIVE: To evaluate the effects of acetaminophen, naproxen, and acetylsalicylic acid on the pharmacokinetics of the centrally acting analgesic tapentadol in healthy subjects. DESIGN: Two randomized, open-label, crossover, drug-drug interaction studies. SETTING: Clinical research facilities in the United States and Belgium. PARTICIPANTS: Twenty-four healthy adults (2-way crossover study) and 38 healthy adults (3-way crossover study). INTERVENTIONS: In both studies, tapentadol immediate release (IR) 80 mg was administered as a single oral dose alone. In the 2-way crossover study, tapentadol IR was also given with the fifth of seven doses of acetaminophen 1000 mg; in the 3-way crossover study, tapentadol IR was also given with the third of four doses of naproxen 500 mg and the second of two doses of acetylsalicylic acid 325 mg. All treatments were separated by a washout period of 7-14 days. MEASUREMENTS AND MAIN RESULTS: Overall, mean serum concentrations were similar after administration of tapentadol IR alone and after coadministration with acetaminophen or acetylsalicylic acid, and the 90% confidence intervals (CIs) for the ratios of the mean area under the serum concentration-time curve (AUC) from time zero to time of the last measurable concentration (AUC(0-t)) and from time zero extrapolated to infinity (AUC(0-infinity)) and the maximum serum concentration (C(max)) of the combined treatments to those parameters of tapentadol alone were well within 80-125%, representing the accepted range for bioequivalence. Coadministration of naproxen did not significantly alter the C(max) of tapentadol, although a slightly higher serum tapentadol exposure relative to tapentadol alone was observed. Coadministration of naproxen resulted in a mean increase of 17% in AUCs, and the upper limits of the 90% CIs for the ratios of the mean AUC(0-t) and AUC(0-infinity) were slightly outside the upper limit of bioequivalence range of 80-125%(126.47%AUC(0-t) and 126.14%AUC(0-infinity)). CONCLUSION: No clinically relevant changes were noted in the serum concentrations of tapentadol, and accordingly, no dosage adjustments with respect to the investigated pharmacokinetic mechanism of interaction are warranted for the administration of tapentadol given concomitantly with acetaminophen, naproxen, or acetylsalicylic acid.

High absolute bioavailability of methylene blue given as an aqueous oral formulation.

PURPOSE: Methylene blue (MB) has recently been reevaluated for malaria treatment. With the aim of excluding treatment failures due to low bioavailability, we have investigated the absolute bioavailability of MB given as an aqueous oral formulation and its interaction with chloroquine (CQ). METHODS: A phase I study in 16 healthy individuals was performed as a monocenter prospective open randomized intra-individual cross-over comparison of MB single doses [50 mg intravenous (i.v.), 500 mg orally, separated by a 1-week wash-out]. After a second week, the group was split for a randomized parallel group comparison of CQ 750 mg administered orally alone or combined with 500 mg MB orally. RESULTS: Mean MB plasma area under the substrate concentration-time curve (AUC 0-infinity) was 7,639 +/- 3,384 ng/mL*h and 51,171 +/- 17,147 ng/mL*h after i.v. and oral administration, respectively (dosage 1:10), and 76,897 +/- 46,037 ng/mL*h after MB combined with CQ. The absolute bioavailability was 72.3 +/- 23.9%. Co-administration with CQ significantly increased MB plasma concentrations (p

CYP2C19 genotype is a major factor contributing to the highly variable pharmacokinetics of voriconazole.

In vitro data on the metabolism of the antifungal voriconazole suggest that its pharmacokinetics might be influenced by the activity of CYP2C19, CYP2C9, and CYP3A. To elucidate the genetic influence of polymorphic enzymes on voriconazole metabolism, the authors pooled the pharmacokinetic data from 2 interaction studies in which 35 participants were enrolled according to their CYP2C19 genotype to receive a single 400-mg oral dose of voriconazole. Nine participants were homozygous for CYP2C19(*)1/(*)1, 8 heterozygous for (*)1/(*)17, 11 heterozygous for (*)1/(*)2, 2 heterozygous for (*)2/(*)17, 4 homozygous for (*)2/(*)2, and 1 with a double mutation CYP2C19(*)2/(*)2(*)17. Nine (heterozygous) individuals were carriers of the CYP2C9(*)2 or (*)3 variant alleles. Twenty-five participants did not express the CYP3A5 isozyme ((*)3/(*)3), whereas in 5 individuals, the (*)1/(*)3 combination was present (active enzyme). In addition, the CYP2D6 genotype and 2 variants of the drug transporter MDR1 (C3435T and G2677T) were determined. Multiple regression analysis of voriconazole apparent oral clearance revealed that 49% of its variance can be explained solely by the CYP2C19 polymorphism (P < .0001). Including the other polymorphisms into the regression model did not show any significant contribution. The number of variant CYP2C19 alleles therefore explains a substantial part of the wide variability of voriconazole pharmacokinetics, whereas the presence of functional CYP3A5 and the CYP2C9 genotype had no significant impact on voriconazole exposure. Some minor contribution results from the MDR1 C3435T genotype.

Quantification of cationic anti-malaria agent methylene blue in different human biological matrices using cation exchange chromatography coupled to tandem mass spectrometry.

Selective and sensitive methods for the determination of the cationic dye and anti-malarial methylene blue in human liquid whole blood, dried whole blood (paper spot), and plasma depending on protein precipitation and cation exchange chromatography coupled to electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) have been developed, validated according to FDA standards, and applied to samples of healthy individuals and malaria patients within clinical studies. Acidic protein precipitation with acetonitrile and trifluoroacetic acid was used for liquid whole blood and plasma. For the extraction of methylene blue from paper spots aqueous acetonitrile was used. Sample extracts were chromatographed on a mixed mode column (cation exchange/reversed phase, Uptisphere MM1) using an aqueous ammonium acetate/acetonitrile gradient. Methylene blue was quantified with MS/MS in the selected reaction monitoring mode using ESI and methylene violet 3RAX as internal standard. Depending on the sample volume (whole blood and plasma 250 microL, and 100 microL on paper spots) the method was linear at least within 75 and 10,000 ng/mL and the limit of quantification in all matrices was 75 ng/mL. Batch-to-batch accuracies of the whole blood, plasma, and paper spot methods varied between -4.5 and +6.6%, -3.7 and +7.5%, and -5.8 and +11.1%, respectively, with corresponding precision ranging from 3.8 to 11.8% CV. After a single oral dose (500 mg) methylene blue concentrations were detectable for 72 h in plasma. The methods were applied within clinical studies to samples from healthy individuals and malaria patients from Burkina Faso.

Methylene blue for malaria in Africa: results from a dose-finding study in combination with chloroquine.

The development of safe, effective and affordable drug combinations against malaria in Africa is a public health priority. Methylene blue (MB) has a similar mode of action as chloroquine (CQ) and has moreover been shown to selectively inhibit the Plasmodium falciparum glutathione reductase. In 2004, an uncontrolled dose-finding study on the combination MB-CQ was performed in 435 young children with uncomplicated falciparum malaria in Burkina Faso (CQ monotherapy had a > 50% clinical failure rate in this area in 2003). Three serious adverse events (SAE) occurred of which one was probably attributable to the study medication. In the per protocol safety analysis, there were no dose specific effects. The overall clinical and parasitological failure rates by day 14 were 10% [95% CI (7.5%, 14.0%)] and 24% [95% CI (19.4%, 28.3%)], respectively. MB appears to have efficacy against malaria, but the combination of CQ-MB is clearly not effective in the treatment of malaria in Africa.

Potent cytochrome P450 2C19 genotype-related interaction between voriconazole and the cytochrome P450 3A4 inhibitor ritonavir.

OBJECTIVES: Cytochrome P450 (CYP) 2C19 and CYP3A4 are the major enzymes responsible for voriconazole elimination. Because the activity of CYP2C19 is under genetic control, the extent of inhibition with a CYP3A4 inhibitor was expected to be modulated by the CYP2C19 metabolizer status. This study thus assessed the effect of the potent CYP3A4 inhibitor ritonavir after short-term administration on voriconazole pharmacokinetics in extensive metabolizers (EMs) and poor metabolizers (PMs) of CYP2C19. METHODS: In a randomized, placebo-controlled crossover study, 20 healthy participants who were stratified according to CYP2C19 genotype received oral ritonavir (300 mg twice daily) or placebo for 2 days. Together with the first ritonavir or placebo dose, a single oral dose of 400 mg voriconazole was administered. Voriconazole was determined in plasma and urine by liquid chromatography-mass spectrometry, and pharmacokinetic parameters were estimated by noncompartmental analysis. RESULTS: When given alone, the apparent oral clearance of voriconazole after single oral dosing was 26%+/-16% (P > .05) lower in CYP2C19*1/*2 individuals and 66%+/-14% (P < .01) lower in CYP2C19 PMs. The addition of ritonavir caused a major reduction in voriconazole apparent oral clearance (354+/-173 mL/min versus 202+/-139 mL/min, P = .0001). This reduction occurred in all CYP2C19 genotypes (463+/-168 mL/min versus 305+/-112 mL/min [P = .023] for *1/*1, 343+/-127 mL/min versus 190+/-93 mL/min [P = .008] for *1/*2, and 158+/-54 mL/min versus 22+/-11 mL/min for *2/*2) and is probably caused by inhibition of CYP3A4-mediated voriconazole metabolism. CONCLUSIONS: Coadministration of a potent CYP3A4 inhibitor leads to a higher and prolonged exposure with voriconazole that might increase the risk of the development of adverse drug reactions on a short-term basis, particularly in CYP2C19 PM patients.

Pharmacokinetics of a netilmicin loading dose on the first postnatal day in preterm neonates with very low gestational age.

OBJECTIVE: Pharmacokinetic parameters are important for dose adjustment of aminoglycosides, but they are highly variable in neonates. In this study the pharmacokinetics of a netilmicin loading dose was investigated on the first postnatal day in preterm neonates with very low gestational age (GA). METHODS: In an open prospective study, 20 neonates with GA between 22.9 and 32.0 weeks and suspected postnatal bacterial infection received an intravenous loading dose of 5 mg/kg netilmicin over 1 h during the first postnatal day. Netilmicin serum concentrations were determined by an enzyme multiplied immunoassay. RESULTS: The systemic clearance of netilmicin normalized to body weight (BW) was not significantly different in three GA subgroups (0.59+/- 0.02 ml/min/kg for GA <24 weeks, 0.72+/-0.14 ml/min/kg for GA 24-27 weeks, and 0.62+/-0.19 ml/min/kg for GA 27-32 weeks, P=0.123). Similar results were also obtained for serum elimination half-time and for the distribution volume normalized to BW. Multiple regression analysis showed that systemic clearance and volume of distribution (both not normalized to BW) significantly correlated with BW (P<0.0001) but not with GA. In the entire group, 20% of peak concentrations were below the target of 6 mg/l, and 63% of trough concentrations were above the target of 2 mg/l. CONCLUSION: In neonates with very low GA, the pharmacokinetic parameters of netilmicin determined after an intravenous loading dose were not dependent on GA when normalized to BW. A number of neonates did not reach targeted peak and trough netilmicin serum concentrations, suggesting that a higher loading dose and a prolonged dosing interval might enhance the effectiveness and safety of netilmicin in preterm neonates immediately after birth.

Safety of the methylene blue plus chloroquine combination in the treatment of uncomplicated falciparum malaria in young children of Burkina Faso [ISRCTN27290841].

BACKGROUND: Safe, effective and affordable drug combinations against falciparum malaria are urgently needed for the poor populations in malaria endemic countries. Methylene blue (MB) combined with chloroquine (CQ) has been considered as one promising new regimen. OBJECTIVES: The primary objective of this study was to evaluate the safety of CQ-MB in African children with uncomplicated falciparum malaria. Secondary objectives were to assess the efficacy and the acceptance of CQ-MB in a rural population of West Africa. METHODS: In this hospital-based randomized controlled trial, 226 children (6-59 months) with uncomplicated falciparum malaria were treated in Burkina Faso. The children were 4:1 randomized to CQ-MB (n = 181; 25 mg/kg CQ and 12 mg/kg MB over three days) or CQ (n = 45; 25 mg/kg over three days) respectively. The primary outcome was the incidence of severe haemolysis or other serious adverse events (SAEs). Efficacy outcomes were defined according to the WHO 2003 classification system. Patients were hospitalized for four days and followed up until day 14. RESULTS: No differences in the incidence of SAEs and other adverse events were observed between children treated with CQ-MB (including 24 cases of G6PD deficiency) compared to children treated with CQ. There was no case of severe haemolysis and also no significant difference in mean haemoglobin between study groups. Treatment failure rates were 53.7% (95% CI [37.4%; 69.3%]) in the CQ group compared to 44.0% (95% CI [36.3%; 51.9%]) in the CQ-MB group. CONCLUSION: MB is safe for the treatment of uncomplicated falciparum malaria, even in G6PD deficient African children. However, the efficacy of the CQ-MB combination has not been sufficient at the MB dose used in this study. Future studies need to assess the efficacy of MB at higher doses and in combination with appropriate partner drugs.

Opposite effects of short-term and long-term St John's wort intake on voriconazole pharmacokinetics.

OBJECTIVES: Constituents of St John's wort (SJW) in vivo induce the cytochrome P450 (CYP) isozymes 3A4, 2C9, and 2C19 but in vitro were shown to inhibit them. This study investigates both short- and long-term effects of SJW on the antifungal voriconazole, which is metabolized by these enzymes. METHODS: In a controlled, open-label study, single oral doses of 400 mg voriconazole were administered to 16 healthy men stratified for CYP2C19 genotype before and on day 1 and day 15 of concomitant SJW intake (300 mg LI 160 3 times daily). Plasma and urine concentrations of voriconazole were determined by liquid chromatography with mass-spectrometric detection. RESULTS: During the initial 10 hours of the first day of SJW administration, the area under the voriconazole plasma concentration-time curve was increased by 22% compared with control (15.5 +/- 6.84 h . microg/mL versus 12.7 +/- 4.16 h . microg/mL, P = .02). After 15 days of SJW intake, the area under the plasma concentration-time curve from hour 0 to infinity was reduced by 59% compared with control (9.63 +/- 6.03 h . microg/mL versus 23.5 +/- 15.6 h . microg/mL, P = .0004), with a corresponding increase in oral voriconazole clearance (CL/F) from 390 +/- 192 to 952 +/- 524 mL/min (P = .0004). The baseline CL/F of voriconazole and the absolute increase in CL/F were smaller in carriers of 1 or 2 deficient CYP2C19*2 alleles compared with wild-type individuals (P < .03). CONCLUSIONS: Coadministration of SJW leads to a short-term but clinically irrelevant increase followed by a prolonged extensive reduction in voriconazole exposure. SJW might put CYP2C19 wild-type individuals at highest risk for potential voriconazole treatment failure.