Group-by-Treatment Interaction Effects in Comparative Bioavailability Studies

Comparative bioavailability studies often involve multiple groups of subjects for a variety of reasons, such as clinical capacity limitations. This raises questions about the validity of pooling data from these groups in the statistical analysis and whether a group-by-treatment interaction should be evaluated. We investigated the presence or absence of group-by-treatment interactions through both simulation techniques and a meta-study of well-controlled trials. Our findings reveal that the test falsely detects an interaction when no true group-by-treatment interaction exists. Conversely, when a true group-by-treatment interaction does exist, it often goes undetected. In our meta-study, the detected group-by-treatment interactions were observed at approximately the level of the test and, thus, can be considered false positives. Testing for a group-by-treatment interaction is both misleading and uninformative. It often falsely identifies an interaction when none exists and fails to detect a real one. This occurs because the test is performed between subjects in crossover designs, and studies are powered to compare treatments within subjects. This work demonstrates a lack of utility for including a group-by-treatment interaction in the model when assessing single-site comparative bioavailability studies, and the clinical trial study structure is divided into groups.

Pharmacokinetics of a Modified-Release Dexamphetamine Sulfate Formulation Following Single and Multiple Dosing in Healthy Adults: Comparative Bioavailability with Immediate-Release Dexamphetamine Sulfate, between Strengths, Assessment of Food and Meal Composition Effects

Background

A modified-release dexamphetamine sulfate formulation (DEX-MR) is under development for the treatment of attention-deficit/hyperactivity disorder.

Objective

We investigated the bioequivalence of once-daily DEX-MR to twice-daily immediate-release dexamphetamine sulfate (DEX-IR) after single and multiple dosing and between strengths, and effects of food and meal types.

Method

Three randomized, open-label, crossover studies in healthy males were conducted. In the single-dose study, participants received DEX-MR 20 mg, DEX-MR 10 mg (20 mg dose), and twice-daily DEX-IR 10 mg under fasted conditions and after a high-fat, high-calorie breakfast. In the breakfast study, participants received DEX-MR 20 mg and twice-daily DEX-IR 10 mg after a normocaloric and a high-fat, high-calorie breakfast. In the multiple-dose study, participants received DEX-MR 20 mg and twice-daily DEX-IR 10 mg for seven days each. In the run-in period (five days), participants consumed a normocaloric breakfast; on profile days, participants consumed a normocaloric breakfast (day 6) or a high-fat, high-calorie breakfast (day 7).

Results

Once-daily DEX-MR at a dose of 20 mg was bioequivalent to twice-daily DEX-IR 10 mg after single dosing under fasted and fed conditions and after multiple dosing under fed conditions. DEX-MR 10 mg and DEX-MR 20 mg were bioequivalent when administered as a single 20 mg dose. Food slightly reduced the rate and extent of absorption of DEX-MR and delayed the time to peak plasma concentration (tmax) by approximately two hours compared to the fasted state. Bioavailability of DEX-MR was comparable under different meal conditions (normocaloric vs. high-fat, high-calorie breakfast) both after single and multiple dosing.

Conclusions

Bioequivalence of once-daily DEX-MR and twice-daily DEX-IR was established. 1×2 DEX-MR 10 mg was bioequivalent to 1×1 DEX-MR 20 mg. DEX-MR should be administered with/after a meal to achieve the targeted pharmacokinetic profile (delayed tmax). Bioavailability of DEX-MR is not affected by meal composition (i.e., fat and caloric content).

Critical Remarks on Reference-Scaled Average Bioequivalence

Purpose: More than a decade ago the option to assess highly variable drugs / drug products by reference-scaled average bioequivalence was introduced in regulatory practice. Recommended approaches differ between jurisdictions and may lead to different conclusions even for the same data set. According to our knowledge, implemented methods have not been directly compared for their operating characteristics (Type I Error and power). Methods: We performed Monte Carlo simulations to assess the consumer risk and the clinically relevant difference for the recommended regulatory settings. Results: In all methods for reference-scaled average bioequivalence the Type I Error can be inflated with a consequently compromised consumer risk. Furthermore, the clinically relevant difference could vary between studies performed with the same reference product. Conclusions: Only average bioequivalence with fixed – widened – limits would both maintain the consumer risk and offer an unambiguously defined clinically not relevant difference. As long as such an approach is not implemented in regulatory practice, we recommend adjusting the level of the test a.

Assessing goodness-of-fit for evaluation of dose-proportionality

For the clinical development of a new drug, the determination of dose-proportionality is an essential part of the pharmacokinetic evaluations, which may provide early indications of non-linear pharmacokinetics and may help to identify sub-populations with divergent clearances. Prior to making any conclusions regarding dose-proportionality, the goodness-of-fit of the model must be assessed to evaluate the model performance. We propose the use of simulation-based visual predictive checks to improve the validity of dose-proportionality conclusions for complex designs. We provide an illustrative example and include a table to facilitate review by regulatory authorities.

An iterative method to protect the type I error rate in bioequivalence studies under two-stage adaptive 2×2 crossover designs

Bioequivalence studies are the pivotal clinical trials submitted to regulatory agencies to support the marketing applications of generic drug products. Average bioequivalence (ABE) is used to determine whether the mean values for the pharmacokinetic measures determined after administration of the test and reference products are comparable. Two-stage 2×2 crossover adaptive designs (TSDs) are becoming increasingly popular because they allow making assumptions on the clinically meaningful treatment effect and a reliable guess for the unknown within-subject variability. At an interim look, if ABE is not declared with an initial sample size, they allow to increase it depending on the estimated variability and to enroll additional subjects at a second stage, or to stop for futility in case of poor likelihood of bioequivalence. This is crucial because both parameters must clearly be prespecified in protocols, and the strategy agreed with regulatory agencies in advance with emphasis on controlling the overall type I error. We present an iterative method to adjust the significance levels at each stage which preserves the overall type I error for a wide set of scenarios which should include the true unknown variability value. Simulations showed adjusted significance levels higher than 0.0300 in most cases with type I error always below 5%, and with a power of at least 80%. TSDs work particularly well for coefficients of variation below 0.3 which are especially useful due to the balance between the power and the percentage of studies proceeding to stage 2. Our approach might support discussions with regulatory agencies.

Reference Datasets for Studies in a Replicate Design Intended for Average Bioequivalence with Expanding Limits

In order to help companies qualify and validate the software used to evaluate bioequivalence trials in a replicate design intended for average bioequivalence with expanding limits, this work aims to define datasets with known results. This paper releases 30 reference datasets into the public domain along with proposed consensus results. A proposal is made for results that should be used as validation targets. The datasets were evaluated by seven different software packages according to methods proposed by the European Medicines Agency. For the estimation of CV_wR and Method A, all software packages produced results that are in agreement across all datasets. Due to different approximations of the degrees of freedom, slight differences were observed in two software packages for Method B in highly incomplete datasets. All software packages were suitable for the estimation of CV_wR and Method A. For Method B, different methods for approximating the denominator degrees of freedom could lead to slight differences, which eventually could lead to contrary decisions in very rare borderline cases.

Sample size determination in bioequivalence studies using statistical assurance

AIMS

Bioequivalence (BE) trials aim to demonstrate that the 90% confidence interval of the T/R-ratio of the pharmacokinetic metrics between two formulations (test [T] and reference [R]) of a drug is fully included in the acceptance interval [0.80, 1.25]. Traditionally, the sample size of BE trials is based on a power calculation based on the intrasubject variability coefficient of variation (CV) and the T/R-ratio of the metrics. Since the exact value of the T/R-ratio is not known prior to the trial, it is often assumed that the difference between the treatments does not exceed 5%. Hence, uncertainty about the T/R-ratio is expressed by using a fixed value for the sample size calculation. We propose to characterise the uncertainty about the T/R-ratio by a (normal) distribution for the log(T/R-ratio), with an assumed mean of  log θ = 0.00 (i.e. θ = 1.00) and a standard deviation σ_u , which quantifies the uncertainty. Evaluating this distribution leads to the statistical assurance of the BE trial.

METHODS

The assurance of a clinical trial can be derived by integrating the power over the distribution of the input parameters, in this case, the assumed distribution of the log(T/R)-ratio. Because it is an average power, the assurance can be interpreted as a measure of the probability of success that does not depend on a specific assumed value for the log(T/R)-ratio. The relationship between power and assurance will be analysed by comparing the numerical outcomes.

RESULTS

Using the assurance concept, values of the standard deviation for the distribution of potential log(T/R)-ratios can be chosen to reflect the magnitude of uncertainty. For most practical cases (i.e. when 0.95 ≤ θ ≤ 1.05), the sample size is not, or only slightly, changed when σ = |log(θ)|.

CONCLUSION

The advantage of deriving the assurance for BE trials is that uncertainty is directly expressed as a parameter of variability.

Pharmacokinetic modelling and validation of the half-life extension needed to reduce the burden of infusions compared with standard factor VIII

INTRODUCTION

Currently, no universally accepted definition of extended half-life (EHL) recombinant FVIII (rFVIII) exists. Identifying the minimum half-life extension ratio required for a reduction in dosing frequency compared with standard rFVIII could enable a more practical approach to decisions around prophylaxis with EHL rFVIII.

AIM

To identify the half-life extension ratio required to decrease rFVIII dosing frequency by at least 1 day while maintaining the proportion of patients with plasma rFVIII levels above 1 IU/dL and without increasing the total weekly dose.

METHODS

A previously published population pharmacokinetic model for standard rFVIII was used to estimate the percentage of patients with factor VIII (FVIII) levels always >1 IU/dL using various benchmark regimens. Using modelling, dosing frequency was reduced while rFVIII half-life was extended until the percentage of patients with FVIII >1 IU/dL equalled that of the benchmark regimen.

RESULTS

Benchmark 3×/wk dosing totalling 100 IU/kg/wk of rFVIII resulted in 56.6% of patients with FVIII levels always >1 IU/dL. With 2×/wk dosing, totalling 80 or 90 IU/kg/wk, half-life extensions required to maintain 56.6% of patients at FVIII levels >1 IU/dL were 1.30 and 1.26, respectively. A half-life extension ratio of 1.33 was required to change dosing from every 48 hours to every 72 hours (both at 105 IU/kg/wk) while maintaining 92.8% of patients with FVIII >1 IU/dL.

CONCLUSION

Based on this investigation, EHL rFVIII products should have a minimum half-life extension ratio of 1.3 to provide a reduction in dosing frequency from 3× to 2×/wk compared with standard rFVIII products while maintaining the same minimum FVIII trough level.

Reference datasets for bioequivalence trials in a two-group parallel design

In order to help companies qualify and validate the software used to evaluate bioequivalence trials with two parallel treatment groups, this work aims to define datasets with known results. This paper puts a total 11 datasets into the public domain along with proposed consensus obtained via evaluations from six different software packages (R, SAS, WinNonlin, OpenOffice Calc, Kinetica, EquivTest). Insofar as possible, datasets were evaluated with and without the assumption of equal variances for the construction of a 90% confidence interval. Not all software packages provide functionality for the assumption of unequal variances (EquivTest, Kinetica), and not all packages can handle datasets with more than 1000 subjects per group (WinNonlin). Where results could be obtained across all packages, one showed questionable results when datasets contained unequal group sizes (Kinetica). A proposal is made for the results that should be used as validation targets.

Two-stage designs in bioequivalence trials

PURPOSE

The aim of this study is to assess the current status of non-fixed sample size designs in bioequivalence trials with a focus on two-stage adaptive approaches.

METHODS

We searched PubMed and Google Scholar from inception to October 2014. Regulatory guidelines were obtained from the public domain. Different methods were compared by Monte Carlo simulations for their impact on the patient's and producer's risks.

RESULTS

Add-on designs, group sequential designs and adaptive two-stage sequential designs are currently accepted to demonstrate bioequivalence in various regulations. All three approaches may inflate the patient's risk if applied inconsiderately. Direct transfer of methods developed for superiority testing to bioequivalence is not warranted. Published two-stage frameworks maintain the type I error and generally the desired power. Adaptation based on the observed T/R ratio observed in the first stage should be applied with caution. Monte Carlo simulations are an efficient tool to explore the operating characteristics of methods.

CONCLUSIONS

Validated two-stage frameworks can be applied without requiring the sponsor to perform own simulations-which could further improve power based on additional assumptions. Two-stage designs are both ethical and economical alternatives to fixed sample designs.

Impact of data base structure in a successful in vitro-in vivo correlation for pharmaceutical products

The in vitro-in vivo correlation (IVIVC) (Food and Drug Administration 1997) aims to predict performances in vivo of a pharmaceutical formulation based on its in vitro characteristics. It is a complex process that (i) incorporates in a gradual and incremental way a large amount of information and (ii) requires information from different properties (formulation, analytical, clinical) and associated dedicated treatments (statistics, modeling, simulation). These results in many studies that are initiated and integrated into the specifications (quality target product profile, QTPP). This latter defines the appropriate experimental designs (quality by design, QbD) (Food and Drug Administration 2011, 2012) whose main objectives are determination (i) of key factors of development and manufacturing (critical process parameters, CPPs) and (ii) of critical points of physicochemical nature relating to active ingredients (API) and critical quality attribute (CQA) which may have implications in terms of efficiency, safety, and inoffensiveness for the patient, due to their non-inclusion. These processes generate a very large amount of data that is necessary to structure. In this context, the storage of information in a database (DB) and the management of this database (database management system, DBMS) become an important issue for the management of projects and IVIVC and more generally for development of new pharmaceutical forms. This article describes the implementation of a prototype object-oriented database (OODB) considered as a tool, which is helpful for decision taking, responding in a structured and consistent way to the issues of project management of IVIVC (including bioequivalence and bioavailability) (Food and Drug Administration 2003) necessary for the implementation of QTPP.

Reference datasets for 2-treatment, 2-sequence, 2-period bioequivalence studies

It is difficult to validate statistical software used to assess bioequivalence since very few datasets with known results are in the public domain, and the few that are published are of moderate size and balanced. The purpose of this paper is therefore to introduce reference datasets of varying complexity in terms of dataset size and characteristics (balance, range, outlier presence, residual error distribution) for 2-treatment, 2-period, 2-sequence bioequivalence studies and to report their point estimates and 90% confidence intervals which companies can use to validate their installations. The results for these datasets were calculated using the commercial packages EquivTest, Kinetica, SAS and WinNonlin, and the non-commercial package R. The results of three of these packages mostly agree, but imbalance between sequences seems to provoke questionable results with one package, which illustrates well the need for proper software validation.

Die absolute Entkoppelung ist möglich

Die EU strebt in ihrer Strategie „Europa 2020“ eine absolute Entkopplung der Wirtschaftsleistungen vom Verbrauch natürlicher Ressourcen an. Doch ist Wirtschaftswachstum mit einer gleichzeitigen Reduktion der Ressourcennutzung möglich?

[UV risk perception by the general public: results of a representative questionnaire in Germany]

AIM OF THE STUDY

For public health promotion purposes it is important to know how the general public perceives the risk factor "UV exposure" and how UV risk perception is connected to health-related attitudes and beliefs. The aim of the study was to collect representative data about UV risk perception in Germany.

METHODS

A representative telephone survey using the ADM design was carried out among 1 501 German residents between May and July 2007. Variables related to UV risk knowledge, relevance of risk topics in every-day thinking and risk estimates were investigated. Data regarding a subjective benefit evaluation of UV exposition was also collected.

RESULTS

The results suggest no essential gaps in the general knowledge about UV risks, except for the underestimation of UV-related cataracts. The respondents thought it extremely likely that UV exposure would cause health damage such as skin cancer, photoaging or sun burns. People were asked to report how often they had thought about a number of health risks including UV risks in the last two weeks. It was established that UV risks are present but not dominant in people's every-day thinking. Along with it, the risk evaluation proves to be rather moderate. The mean value for respondents' perceived personal risk is M=5.1, in the midsection of the given 10-point scale. The results show that perceived personal risk is not influenced by the serious UV health risks such as cancer or cataracts. The results also indicate that UV benefit and UV risk perception are not strongly related to one another.

CONCLUSIONS

In summary, participants' perception and assessment of the various health risks of UV exposure seem to be realistic, but the UV risk assessment it is not related to the perception of personal risk. One must therefore assume that UV health risk information and education campaigns do not necessarily lead to a change in the perception of personal UV risk. Rather than addressing primarily risk knowledge, UV risk communication should focus more on motivational aspects and consider the role of UV benefit perception.

The neural basis of risk ratings: Evidence from a functional magnetic resonance imaging (fMRI) study

Research investigating risk perception suggests that not only the quantitative parameters used in technical risk assessment (i.e., frequency and severity of harm) but also 'qualitative' aspects such as the dread a hazard provokes or its controllability influence risk judgments. It remains to be elucidated, however, which neural mechanism underlie risk ratings in healthy subjects. Using fMRI to detect changes in neural activity we compared the neural activations elicited by risk ratings with those elicited by a letter detection task performed on the same stimuli. The latter task served to control for basic stimulus processing, response selection and button-pressing during task performance. Risk ratings differentially activated the medial prefrontal cortex, the inferior frontal gyrus, the cerebellum (P<0.05, FWE corrected, whole brain approach), and in an additional ROI analysis the amygdala (P<0.05, FWE corrected). Of these structures, particularly the amygdala and the prefrontal cortex have been previously associated with decisions about affective interference. Furthermore our data suggest both, similarities and differences between the neural correlates of risk ratings and risk taking as involved, for e.g., in gambling tasks.

Bioequivalence of a methylphenidate hydrochloride extended-release preparation: comparison of an intact capsule and an opened capsule sprinkled on applesauce

OBJECTIVE

To assess bioequivalence between an intact capsule and the content of a capsule sprinkled on applesauce.

MATERIALS

Medikinet retard 20 mg capsules were obtained from Medice (Iserlohn, Germany).

METHODS

This was a single-center, completely randomized, open, 2-period, 2-sequence, balanced crossover study with a washout period of 1 week between administrations, in 12 healthy male and female subjects, aged 18-45 years. Blood samples were collected over 24 hours and methylphenidate plasma concentration-time data were used to calculate pharmacokinetic parameters for both administrations. The main parameters were (confirmatory) AUC0-tz (extent of BA), Cmax, tmax (rate of BA) and (descriptively) AUC0-infinity and t1/2. Equivalence was concluded if the 90% confidence interval (CI) for the ratio between test and reference was 0.80-1.25 (AUC0-tz).

RESULTS

All 12 dosed subjects finished both treatment periods and were included in pharmacokinetic and safety analyses. 90% geometric confidence intervals for AUC0-tz and Cmax data were well within accepted bioequivalence limits. The study has shown that both treatment modes lead to similar pattern of absorption and elimination following single-dose administration in the fed state. The test treatment (content of capsule sprinkled over 15 ml applesauce) is bioequivalent to the reference treatment (intact capsule) in terms of extent and rate of absorption.

CONCLUSION

Data collected from this study demonstrate that Medikinet retard capsules can be opened and the content sprinkled on a tablespoon of applesauce without influencing the rate and extent of bioavailability.

SAR-Werte von Mobiltelefonen

The specific absorption rate (SAR) is a prominent topic in the discussion about precautionary health protection. An experimental study investigated the effect of information about various SAR values (below the existing partial body limit value of 2 W/kg) on safety judgments of potential mobile phones users. It turns out that about 94% of the participants do not know the SAR value of their own mobile phone. SAR values below existing limits are not perceived as equally safe. Rather, the lower the SAR value, the higher the perceived safety. However, a majority of the participants does not consider these SAR values to be 100% safe, even if they are clearly below the existing limits. Explicitly indicating a precautionary limit value (referring to the Federal Office for Radiation Protection or to consumer organizations) does not change this safety evaluation. As expected, safety evaluation of the SAR values is also related to the perception of mobile phone risks. Those who are concerned about mobile phone communication give lower safety judgments than the unconcerned-independent of the level of the SAR values. Irrespective of that, our results suggest that establishing the SAR value as a criterion for mobile phones depends first of all on making it known to the public.

Intraventricular cytarabine in a case of idiopathic hypertrophic pachymeningitis

Idiopathic hypertrophic chronic pachymeningitis (IHCP) is characterised by inflammatory fibrotic thickening of the dura mater. Long term management is controversial. A 28 year old man with craniospinal IHCP and prominent lymphocytic meningitis is reported. Cerebrospinal fluid and histological examination suggested a CD4+ T cell driven process and B cell stimulation. After surgical, tuberculostatic, and immunosuppressive treatment failed to control the progressive meningeal hypertrophy, causing severe headache and neurological disability, the disease process eventually abated with intraventricular cytarabine treatment.

Risiken beim Drogenscreening mit Immunoassays

Now-a-days immunoassays are world wide used for the rapid screening of drugs. Despite the fact that they are a highly valuable tool for the test of legal and illicit drugs, there is a non-negligible risk of false positive and false negative findings and many pitfalls must be taken into account when using these tests in an uncritical manner and without valid confirmation procedures.

Multiple homicides as a result of chloroform poisoning: case report and experimental study

Two cases (involving five murder victims) of multiple homicide by inhalational chloroform intoxication are reported. In the discussion of the findings the valence of toxicological analyses is underlined with regard to the possibility of forcible external suffocation due to occlusion of the respiratory orifices by means of a chloroform-soaked soft covering. In addition storage experiments were performed at +4, +20 and -20 degrees C with cadaver blood mixed with chloroform. The optimal solution for avoiding volatile losses was stored in glass tubes with ground glass stoppers. In cases of unclear death in which involvement of volatile substances is suspected it is, therefore, advisable to preserve an additional blood sample at -20 degrees C in glass tubes that are only opened for the analysis of volatile substances.

[Detection of the cholinesterase inhibitor tacrine and its main metabolites]

Tacrine, a cholinesterase inhibitor for symptomatic treatment of minor to moderate dementia, and its primary metabolites 1-hydroxy-tacrine and 4-hydroxy-tacrine were studied by means of thin-layer chromatography, UV spectroscopy and gas-chromatography/mass spectroscopy. The analytical data (corrected hRf values, UV spectra in solution as well as reflectance spectra, high-pressure liquid chromatography data, GC retention indices and EI mass spectra) including various derivatization methods are described.

Evidence for a DNA triplex in a recombination-like motif: I. Recognition of Watson-Crick base pairs by natural bases in a high-stability triplex

Data are presented on a triplex type with two parallel homologous strands for which triplex formation is almost as strong as duplex formation at least for some sequences and even at pH 7 and 0.2 M NaCl. The evidence mainly rests upon comparing thermodynamic properties of similar systems. A paperclip oligonucleotide d(A12C4T12C4A12) with two linkers C4 obviously can form a triplex with parallel back-folded adenine strand regions, because the single melting transition of this complex splits in two transitions by introducing mismatches only in the third strand region. Respectively, a hairpin duplex d(A12C4T12) and a single strand d(A12) form a triplex as a 1:1 complex in which the second adenine strand is parallel oriented to the homologous one in the Watson-Crick paired duplex. In this system the melting temperature T(m) of the triplex is practically the same as that of the duplex d(A12)-d(T12), at least within a complex concentration range of 0.2-4.0 microM. The melting behaviour of complexes between triplex stabilizing ligand BePI and the system hairpin duplex plus single strand supports the triplex model. Non-denaturing gel electrophoresis suggests the existence of a triplex for a system in which five of the twelve A-T*A base triads are substituted by C-G*C base triads. The recognition between any substituted Watson-Crick base pair (X-Y) in the hairpin duplex d(A4XA7C4T7YT4) and the correspondingly replaced base (Z) in the third strand d(A4ZA7) is mutually selective. All triplexes with matching base substitutions (Z = X) have nearly the same stability (T(m) values from 29 to 33.5 degrees C), whereas triplexes with non-matching substitutions (Z not equal X) show a clearly reduced stability (T(m) values from 15 to 22 degrees C) at 2microM equimolar oligonucleotide concentration. Most nucleic acid triple helices hitherto known are limited to homopurine-homopyrimidine sequences in the target duplex. A stable triplex formation is demonstrated for inhomogeneous sequences tolerating at least 50% pyrimidine content in the homologous strands. On the basis of the surprisingly similar thermodynamic parameters for duplex and triplex, and of the fact that this triplex type seems to be more stable than many other natural DNA triplexes known, and on the basis of semiempirical and molecule mechanical calculations, we postulate bridging interactions of the third strand with the two other strands in the triplex according to the recombination motif. This triplex, denoted by us 'recombination-like form', tolerates heterogeneous base sequences.

pH-Dependent dissolving nano- and microparticles for improved peroral delivery of a highly lipophilic compound in dogs

RR01, a new highly lipophilic drug showing extremely low water solubility and poor oral bioavailability, has been incorporated into pH-dependent dissolving particles made of a poly(methacrylic acid-co-ethylacrylate) copolymer. The physicochemical properties of the particles were determined using laser-light-scattering techniques, scanning electron microscopy, high-performance liquid chromatography, and x-ray powder diffraction. Suspension of the free drug in a solution of hydroxypropylcellulose (reference formulation) and aqueous dispersions of pH-sensitive RR01-loaded nanoparticles or microparticles were administered orally to Beagle dogs according to a 2-block Latin square design (n = 6). Plasma samples were obtained over the course of 48 hours and analyzed by gas chromatography/mass spectrometry. The administration of the reference formulation resulted in a particularly high interindividual variability of pharmacokinetic parameters, with low exposure to compound RR01 (AUC0-48h of 6.5 microg x h/mL and coefficient of variation (CV) of 116%) and much higher Tmax, as compared to both pH-sensitive formulations. With respect to exposure and interindividual variability, nanoparticles were superior to microparticles (AUC0-48h of 27.1 microg x h/mL versus 17.7 microg x h/mL with CV of 19% and 40%, respectively), indicating that the particle size may play an important role in the absorption of compound RR01. The performance of pH-sensitive particles is attributed to their ability to release the drug selectively in the upper part of the intestine in a molecular or amorphous form. In conclusion, pH-dependent dissolving particles have a great potential as oral delivery systems for drugs with low water solubility and acceptable permeation properties.

Screening, identification and quantitation of benzodiazepines in serum by solid phase extraction on a cyanopropyl phase using high performance liquid chromatography and photodiode array detection

A screening procedure for benzodiazepines in serum is presented. The compounds are extracted over a cyanopropyl phase followed by identification and determination via high performance liquid chromatography and photodiode array detection. Diazepam (CAS 439-14-5), flunitrazepam (CAS 1622-62-4), nordazepam (CAS 1088-11-5), oxazepam (CAS 604-75-1) and temazepam (CAS 846-50-4) are quantified. Retention data of 42 benzodiazepines and their metabolites as well as hydrolysis products are listed. This assay leads to an expansion of a known systematic toxicological analysis system to identify pharmaceuticals, drugs of abuse and pesticides.

Antibiotic prophylaxis in percutaneous endoscopic gastrostomy (PEG)--results from a prospective randomized multicenter trial

OBJECTIVE

To determine the efficacy of antibiotic prophylaxis in percutaneous endoscopic gastrostomy (PEG) as a part of a standardized regimen.

METHODS

An open prospective randomised multicenter study in 216 patients. 106 received ceftriaxone 1 g i.v. 30 min preinterventionally and 110 no study medication. A standardized protocol was followed for PEG preparation, insertion, and aftercare; all patients received a 15 French gastrostomy tube. Follow-up of local and systemic infection and clinical course was continued to postintervention day 10. An aggregate erythema and exudation score > 3 or the presence of pus was taken as indicative of peristomal infection. The pharmacoeconomics of antibiotic use were also examined.

RESULTS

In no-prophylaxis patients, wound infection rates were 23.6% on day 4 and 24.5% on day 10 vs. 7.6% (p < 0.05) and 11.4% (p < 0.05), respectively, in prophylaxis patients. Results were disproportionally better in tumor patients in comparison with neurological patients. Patients systemic infection rates were 11.8% vs. 1.9% in noprophylaxis vs. prophylaxis (p < 0.05), and overall infection rates 36.3% vs. 13.3%, respectively (p < 0.05). Pneumonia was more frequent in patients with underlying neurological disease and reduced in the prophylaxis group. Antibiotic and application costs were similar in both groups (p = 0.400).

CONCLUSIONS

Single-dose ceftriaxone 1 g is a effective prophylaxis against local and systemic infection after PEG and should be a part of a standard regimen.