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 Î¸ = 0.00 (i.e. θ = 1.00) and a standard deviation σu , 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 ≤ Î¸ ≤ 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.

Locomotor activity, growth hormones, and systemic robusticity: An investigation of cranial vault thickness in mouse lines bred for high endurance running.

OBJECTIVES: To use a mouse model to investigate the relationships among the components of the systemic robusticity hypothesis (SRH): voluntary exercise on wheels, spontaneous physical activity (SPA) in cages, growth hormones, and skeletal robusticity, especially cranial vault thickness (CVT). MATERIALS AND METHODS: Fifty female mice from lines artificially selected for high running (HR) and 50 from nonselected control (C) lines were housed in cages with (Active) or without wheels (Sedentary). Wheel running and SPA were monitored daily. The experiment began at 24-27 days of age and lasted 12 weeks. Food consumption was measured weekly. Mice were skeletonized and their interparietal, parietal, humerus, and femur were µCT scanned. Mean total thickness of the parietal and interparietal bones was determined, along with thickness of the cortical and diploe layers individually. Geometric cross-sectional indicators of strength were calculated for the long bones. Blood samples were assayed for IGF-1 and IGFBP-3. RESULTS: Physical activity differed significantly among groups, based both on linetype (C vs. HR) and activity (A vs. S). However, contrary to our predictions, the ratio of IGF-1 to IGFBP-3 was higher in C mice than in HR mice. Neither CVT nor postcranial robusticity was affected by linetype or activity, nor were most measures of CVT and postcranial robusticity significantly associated with one another. DISCUSSION: Our results fail to provide support for the systemic robusticity hypothesis, suggesting it is important to rethink the long-standing theory that increased CVT in Homo erectus reflects increased physical activity compared other hominin species.

Effect of daytime, weekday and year of admission on outcome in acute ischaemic stroke patients treated with thrombolytic therapy.

BACKGROUND: Since doubts were raised, if a challenging medical procedure such as acute stroke treatment including thrombolysis with recombinant tissue plasminogen activator (rTPA) is available with identical standard and outcome 24 h and 7 days a week our aim was to examine if acute stroke patients defined by onset-admission time (OAT) of

[UV risk perception by the general public: results of a representative questionnaire in Germany]. / UV-Risikowahrnehmung in der Bevölkerung: Ergebnisse einer repräsentativen Umfrage in Deutschland.

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.

Semliki forest virus: cause of a fatal case of human encephalitis.

A fatal case of human encephalitis has been observed for which our results indicate that Semliki Forest virus (SFV) was the etiologic agent. This is surprising in view of the fact that this virus, which has been widely studied, was believed to be one of the arboviruses nonpathogenic for man. Described are the clinical course, the virological examinations performed, and the histopathological findings in the central nervous system.

Lack of bioequivalence between two methylphenidate extended modified release formulations in healthy volunteers.

OBJECTIVE: To assess bioequivalence between Equasym Retard and Medikinet retard containing 20 mg methylphenidate (MPH) hydrochloride in a fed state. MATERIALS: Equasym Retard 20 mg capsules (UCB, Monheim, Germany) and Medikinet retard 20 mg capsules (Medice, Iserlohn, Germany). METHODS: This was an open, single-center, randomized, 2-period, 2-sequence, balanced cross-over study with a wash-out period of 1 week between administrations in 14 healthy male and female volunteers, aged 18 - 45 years. Blood samples were collected over 24 hours and methylphenidate plasma concentration-time data were used to calculate pharmacokinetic metrics for both formulations. The main metrics were AUC0-t and Cmax. Bioequivalence was concluded if the 90% confidence interval (CI) for the ratio between test and reference was 80 - 125% (AUC0-t, Cmax). RESULTS: All dosed subjects finished both treatment periods and were included in pharmacokinetic and safety analyses. The adverse events observed, mainly nervous system disorders (headache), were all mild or moderate in intensity and resolved without any action taken. The adverse event profile was consistent with the currently applicable SmPCs (Summaries of Product Characteristics) for Equasym Retard and Medikinet retard. Geometric means +/- SD for AUC0-t and Cmax were 35.5 +/- 10.1 ng x h/ml and 4.05 +/- 0.96 ng/ml (Equasym Retard) and 39.2 +/- 13.8 ng x h/ml and 5.26 +/- 2.11 ng/ml (Medikinet retard). The 90% geometric confidence interval for AUC0-t (extent of absorption) was within limits accepted for bioequivalence. Bioequivalence could not be demonstrated for the rate of bioavailability (Cmax); both the lower confidence limit and the point estimate were below 80% of the reference. The study has shown that both formulations lead to a similar pattern of absorption and elimination following single dose administration in the fed state, although the test formulation shows a somewhat slimmer profile, where the first peak is less pronounced. No bioequivalence could be shown within the first 4 hours. The second peak of the test was also lower than the one of the reference (both lower confidence limit and point estimate below 80%). CONCLUSIONS: The two formulations are not bioequivalent, especially if the rate and values within the first four hours after administration are taken into account.

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.

Dissolution comparisons using a Multivariate Statistical Distance (MSD) test and a comparison of various approaches for calculating the measurements of dissolution profile comparison.

The f 2 test is generally used for comparing dissolution profiles. In cases of high variability, the f 2 test is not applicable, and the Multivariate Statistical Distance (MSD) test is frequently proposed as an alternative by the FDA and EMA. The guidelines provide only general recommendations. MSD tests can be performed either on raw data with or without time as a variable or on parameters of models. In addition, data can be limited-as in the case of the f 2 test-to dissolutions of up to 85% or to all available data. In the context of the present paper, the recommended calculation included all raw dissolution data up to the first point greater than 85% as a variable-without the various times as parameters. The proposed MSD overcomes several drawbacks found in other methods.

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.

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.

Atrial natriuretic factor controls salt gland secretion in the Pekin duck (Anas platyrhynchos) through interaction with high affinity receptors.

Marine birds possess supraorbital salt-secreting glands in addition to the kidneys as osmoregulatory organs to excrete a strongly hypertonic salt solution of mainly NaCl. Atrial natriuretic factor (ANF)-like peptides could be demonstrated immunocytochemically in duck atria, but not in the salt glands. To elucidate the putative role of bird-specific ANF (cANF) in the control of salt gland function, conscious saltwater-acclimated Pekin ducks received 15 pmol/min.kg BW cANF for 10 min at two states of salt gland activity. During steady state diuresis and salt gland secretion induced by systemic infusion of 1.0 ml/min isotonic Krebs-Ringer solution, cANF applied iv enhanced the secretion rate from 0.20 to 0.29 ml/min and the osmolality of secretion from 870 to 920 mosmol/kg. At threshold conditions of salt gland activity, cANF infused intracarotideally stimulated the secretion rate from 0.07 to 0.15 ml/min at elevated osmolality of 760 compared to 480 mosmol/kg. Mean arterial pressure and heart rate remained unchanged. Receptor autoradiography with [125I]Bolton-Hunter-cANF as ligand demonstrated specific binding sites throughout the salt gland tissue of both freshwater and saltwater ducks. Scatchard analysis using an enriched membrane fraction revealed high affinity (Kd = 0.9 nM) binding sites of 270 fmol/mg protein density. Displacement studies with unlabeled cANF and human ANF showed comparable Ki values for both peptides in freshwater and saltwater ducks. The combined results indicate an important role for cANF in the control of avian salt gland function.

Modulation of kidney function in conscious Pekin ducks by atrial natriuretic factor.

The influence of avian atrial natriuretic factor (ANF) on renal function was examined in conscious saltwater-acclimated Pekin ducks undergoing a steady state diuresis maintained by iv infused isotonic avian Krebs-Ringer solution at a rate of 1.0 ml/min. Synthetic chicken ANF (chANF) was applied iv at doses of 10, 50, and 90 ng/min.kg BW for 10 min and caused dose-dependent transient increases in urine flow, osmolal excretion, glomerular filtration rate, effective renal plasma flow, and fractional water clearance at decreased urinary osmolality. Using receptor autoradiography, binding sites for [125I]Bolton-Hunter-labeled chANF [( 125I]BH-chANF) were localized in both the reptilian-type glomeruli and the collecting duct system throughout the duck kidney. A RRA for [125I]BH-chANF, established using an enriched kidney membrane fraction, indicated that unlabeled chANF and human ANF competitively displaced [125I]BH-chANF with comparable potencies. ANF-induced modulation of renal salt and water elimination via glomerular and tubular receptor interactions is consistent with the concept that this hormone has a physiological role in avian volume homeostasis.

Plasma atrial natriuretic factor responses to blood volume changes in the Pekin duck.

A RIA was developed for the measurement of immunoreactive atrial natriuretic factor (irANF) in avian plasma and was used to investigate the relationship between vascular volume and plasma irANF concentrations in conscious Pekin ducks. In normally hydrated birds, the mean plasma irANF concentration was 78.5 +/- 6.8 pg/ml. Blood volume expansion by iv infusion of isotonic saline at 1 ml/min elevated irANF concentrations by 132% after 1 h and by 233% after 2 h. Reduction of the vascular volume by nonhypotensive hemorrhage of 10% and then 20% of the total blood volume reduced irANF levels by 16% and 42%, respectively, 5 min after blood removal was completed. Similarly, in birds deprived of water for 24 h and with blood volume reduced by 4.8%, plasma irANF concentrations were 50% lower than in the same euhydrated animals. The observed correlation between plasma irANF concentrations and vascular volume is consistent with the concept that ANF has a physiological role in avian volume homeostasis.

Validity of a food frequency questionnaire for the determination of individual food intake.

The validity of a food frequency questionnaire for dietary assessment was tested with 31 college students living and dining in a dormitory. A food frequency questionnaire was mailed to participants requesting them to estimate their usual intake of specific food items. Actual food consumption was determined at each meal with self-report forms. These forms required participants to indicate foods chosen at that meal. To test the validity of the frequency questionnaire, regression equations were calculated for each individual using the frequency questionnaire data as the independent variable (X) and actual intake data as the dependent variable (Y). Eighty-four percent of the r values were greater than 0.50 and 55% were greater than 0.71. All were significant at the 0.002 level or below. As an alternative test of validity, the percentage of over- and underestimation of each food group was also assessed. Foods which are often major components of a meal (eg, flesh foods) were estimated with greater accuracy than those foods which could be considered accessory (eg, nuts or seeds). While it appears that a large percentage of individuals could accurately estimate their intake with this technique, some individuals were unsuccessful in doing so. Further research is needed to identify individual characteristics which may predict success with this technique.

Food supplement usage in seven Western states.

Data on food supplement usage were collected from 2451 adults in seven Western states. No significant differences were determined among states. A majority (66.6%) of the sample used some form of food supplements, with 40.0% consuming one to three supplements per day. The archetype food supplement user was likely to be a young female with some college education, who believes that the nutritional quality of food has decreased in the last 10 yr and in the efficacy of supplements for disease prevention or cure, and primarily receives information concerning food and nutrition from books and health food stores. Correspondingly, one of the most frequently cited reasons for using food supplements, next to "to prevent colds and other illnesses" was "to make up for what is not in food." The three most frequently used food supplements, in rank order, were multiple vitamins, vitamin C, and multiple vitamins plus iron.

Validity of telephoned diet recalls and records for assessment of individual food intake.

Six methods of assessing individual food intake reported by telephone were compared for accuracy. A sample of 107 students eating in a dormitory dining hall was used. Two 7-day and four 3-day diet records were reported by telephone to either an interviewer or an answering device; and fourteen 6-h recalls and seven 24-h recalls were obtained by an interviewer over the telephone. To examine validity, the investigators observed respondents' intake for 28 days. Food item agreement scores comparing observed and reported data were calculated. Seven-day records were most accurate (87% food item agreement); 3-day records and 6-h recalls were equivalent (75%); and 24-h recalls were least accurate (69%). There were no significant difference in accuracy of reporting records to an interviewer versus a recording device, but respondents preferred the interviewer. Results of telephoned reporting compare favorably with personal interview techniques used by other investigators, indicating that telephoned methods should be further explored in community settings.

ANF-induced modulation of ADH-release in the rabbit and Pekin duck.

The atrial natriuretic factor (ANF) as an osmoregulatory hormone causes a reduction of extracellular fluid volume primarily through stimulation of renal and extrarenal water and sodium elimination. Consequently, ANF counteracts the renin-angio-tensin II-aldosterone (RAAS) and the antidiuretic hormone (ADH) systems at their target organ level. The possible direct interaction of ANF with the hypothalamo-neurohypophyseal ADH system was investigated in conscious ducks and rabbits during conditions of eu- and dehydration. In euhydrated animals, the plasma concentration of ADH remained unchanged during the systemic infusion of species-specific ANF, whereas in dehydrated rabbits but not ducks, the plasma concentration of ADH was significantly decreased. These differences in ADH modulation were supported by the localization of binding sites for radiolabeled ANF at the sites of ADH release, the median eminence (ME) and neurohypophysis (NH) of the rabbit but not duck brain, using receptor-autoradiography. For both species, circumventricular organs lacking a functional blood-brain barrier (BBB) such as the subfornical organ (SFO), the organum vasculosum of the laminae terminalis (OVLT), the pineal and the choroid plexus (ChP), as well as the ependymal lining of the third ventricle (VIII) were labeled specifically. Within the BBB, binding sites for ANF could not be detected in the ADH-synthesizing paraventricular (PVN) and supraoptic nuclei (SON) of either species, however, sites were observed in the anterior median nucleus of the hypothalamus (AM) of the duck brain. In the AM as well as the PVN and ME, the existence of a brain-intrinsic ANF system could be demonstrated for the Pekin duck using immunocytochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of large doses of dexamethasone on the cerebrospinal fluid pressure in patients with supratentorial tumors.

The effect of large doses of dexamethasone (80 mg) on the cerebrospinal fluid pressure (CSFP) was investigated with continuous lumbar CSFP measurement over 24 h in 10 patients with supratentorial cerebral tumors and clinical signs of elevated intracranial pressure. There was a further slight rise in CSFP with an unchanged pressure pattern in the course of observation of the untreated control group. A marked lowering of CSFP was observed within 6 h after initial intravenous administration of dexamethasone to seven of the treated patients. In four of the treated patients an unequivocal and in five only a moderate CSFP lowering was measured at the end of the registration. One patient had a slight rise in pressure. The plateau waves of all the patients treated decreased in height, frequency and duration within the first hours, while fluctuations in pressure level and CSFP amplitude were reduced.

Stroke-like episodes in familial mitochondrial encephalomyopathy: clinical and biochemical aspects.

Acute episodes of focal neurological dysfunction are a well-recognized complication of the mitochondrial encephalomyopathies. Because of rapid remission, biochemical tests and other diagnostic procedures are mostly performed after the acute phase. We report the case of a patient suffering from mitochondrial disease manifesting primarily with seizures, progressive deafness and dementia, who experienced multiple stroke-like episodes. Other members of the family with evidence of mitochondrial dysfunction are presented briefly. EEG and biochemical findings in the acute stage are correlated with clinical symptoms, showing characteristics distinct from the chronic illness. The possible involvement of dietary factors in the provocation of stroke-like episodes is discussed and regulation of glucose intake suggested as a strategy in the prevention of stroke-like episodes.