The Need of Industry to Go FAIR

The industry sector is a very large producer and consumer of data, and many companies traditionally focused on production or manufacturing are now relying on the analysis of large amounts of data to develop new products and services. As many of the data sources needed are distributed and outside the company, FAIR data will have a major impact, both by reducing the existing internal data silos and by enabling the efficient integration with external (public and commercial) data. Many companies are still in the early phases of internal data “FAIRification”, providing opportunities for SMEs and academics to apply and develop their expertise on FAIR data in collaborations and public-private partnerships. For a global Internet of FAIR Data & Services to thrive, also involving industry, professional tools and services are essential. FAIR metrics and certifications on individuals, data, organizations, and software, must ensure that data producers and consumers have independent quality metrics on their data. In this opinion article we reflect on some industry specific challenges of FAIR implementation to be dealt with when choices are made regarding “Industry GOing FAIR”.

Nine Principles of Semantic Harmonization

Medical data is routinely collected, stored and recorded across different institutions and in a range of different formats. Semantic harmonization is the process of collating this data into a singular consistent logical view, with many approaches to harmonizing both possible and valid. The broad scope of possibilities for undertaking semantic harmonization do lead however to the development of bespoke and ad-hoc systems; this is particularly the case when it comes to cohort data, the format of which is often specific to a cohort's area of focus. Guided by work we have undertaken in developing the 'EMIF Knowledge Object Library', a semantic harmonization framework underpinning the collation of pan-European Alzheimer's cohort data, we have developed a set of nine generic guiding principles for developing semantic harmonization frameworks, the application of which will establish a solid base for constructing similar frameworks.

A novel subject synchronization clinical trial design for Alzheimer's disease

One of the challenges in developing a viable therapy for Alzheimer's disease has been demonstrating efficacy within a clinical trial. Using this as motivation, we sought to re-examine conventional clinical trial practices in order to determine whether efficacy can be better shown through alternative trial designs and novel analysis methods. In this work, we hypothesize that the confounding factors which hamper the ability to discern a treatment signal are the variability in observations as well as the insidious nature of the disease. We demonstrate that a two-phase trial design in which drug dosing is administered after a certain level of disease severity has been reached, coupled with a method to account more accurately for the progression of the disease, may allow us to compensate for these factors, and thus enable us to make treatment effects more apparent. Utilizing data from two previously failed trials which involved the evaluation of galantamine for indication in mild cognitive impairment, we were able to demonstrate that a clear treatment effect can be realized through both visual and statistical means, and propose that future trials may be more likely to show success if similar methods are utilized.

Sparse learning and stability selection for predicting MCI to AD conversion using baseline ADNI data

Background

Patients with Mild Cognitive Impairment (MCI) are at high risk of progression to Alzheimer’s dementia. Identifying MCI individuals with high likelihood of conversion to dementia and the associated biosignatures has recently received increasing attention in AD research. Different biosignatures for AD (neuroimaging, demographic, genetic and cognitive measures) may contain complementary information for diagnosis and prognosis of AD.

Methods

We have conducted a comprehensive study using a large number of samples from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) to test the power of integrating various baseline data for predicting the conversion from MCI to probable AD and identifying a small subset of biosignatures for the prediction and assess the relative importance of different modalities in predicting MCI to AD conversion. We have employed sparse logistic regression with stability selection for the integration and selection of potential predictors. Our study differs from many of the other ones in three important respects: (1) we use a large cohort of MCI samples that are unbiased with respect to age or education status between case and controls (2) we integrate and test various types of baseline data available in ADNI including MRI, demographic, genetic and cognitive measures and (3) we apply sparse logistic regression with stability selection to ADNI data for robust feature selection.

Results

We have used 319 MCI subjects from ADNI that had MRI measurements at the baseline and passed quality control, including 177 MCI Non-converters and 142 MCI Converters. Conversion was considered over the course of a 4-year follow-up period. A combination of 15 features (predictors) including those from MRI scans, APOE genotyping, and cognitive measures achieves the best prediction with an AUC score of 0.8587.

Conclusions

Our results demonstrate the power of integrating various baseline data for prediction of the conversion from MCI to probable AD. Our results also demonstrate the effectiveness of stability selection for feature selection in the context of sparse logistic regression.

Quantifying the pathophysiological timeline of Alzheimer's disease

Hypothetical models of AD progression typically relate clinical stages of AD to sequential changes in CSF biomarkers, imaging, and cognition. However, quantifying the continuous trajectories proposed by these models over time is difficult because of the difficulty in relating the dynamics of different biomarkers during a clinical trial that is significantly shorter than the duration of the disease. We seek to show that through proper synchronization, it is possible to de-convolve these trends and quantify the periods of time associated with different pathophysiological changes associated with Alzheimer's disease (AD). We developed a model that replicated the observed progression of ADAS-Cog 13 scores and used this as a more precise estimate of disease-duration and thus pathologic stage. We then synchronized cerebrospinal fluid (CSF) and imaging biomarkers according to our new disease timeline. By de-convolving disease progression via ADAS-Cog 13, we were able to confirm the predictions of previous hypothetical models of disease progression as well as establish concrete timelines for different pathobiological events. Specifically, our work supports a sequential pattern of biomarker changes in AD in which reduction in CSF Aβ(42) and brain atrophy precede the increases in CSF tau and phospho-tau.

Biotransformation and excretion of lorazepam in patients with chronic renal failure

To evaluate the effect of end-stage renal insufficiency and haemodialysis on the elimination of lorazepam, single oral doses of the drug (2.5 mg) were administered to normal subjects and patients with chronic renal failure (CC(r) : less than 2 ml/min) in the interdialysis period and during haemodialysis. The concentration of lorazepam and its major metabolite, lorazepam-glucuronide, were assayed using electron capture g.l.c. Plasma half-life (T1/2) of unchanged lorazepam in the patient group (11.3 +/- 0.6 h) was not different from that obtained in normals (11.1 +/- 0.9 h). Only minor quantities of the unchanged drug could be recovered in the 24 h urine in both groups: 0.3% of the ingested dose in normals and trace amounts in the patient group. No unchanged lorazepam could be detected in the ultrafiltrate from the coil kidney. Since the lower sensitivity of the method is about 5 ng/ml, this would indicate the in vivo binding of the active drug to plasma proteins to be at least 70%. The effect of haemodialysis on lorazepam plasma T1/2 was also insignificant (9.4 +/- 1.0 h). Urinary excretion of lorazepam-glucuronide was found to be considerably decreased in chronic renal failure associated with accumulation of high concentrations of this conjugate in plasma during days after a single oral dose. The plasma T1/2 of this conjugate in normals was 20.7 +/- 2.1 h. Roughly 35% of this main metabolite's concentration in plasma was detected in the ultrafiltrate from the coil kidney indicating the dialyzability of this conjugate and that the extent of plasma protein binding of lorazepam-glucuronide in vivo was approximately 65%. The above results indicate that after a single oral dose (2.5 mg) the biotransformation of lorazepam to its glucuronide conjugate remains unaltered and that high concentrations of this metabolite accumulate in plasma in the presence of severe renal function impairment.

The tibialis tendon as a valuable anterior cruciate ligament allograft substitute: biomechanical properties

The study evaluates the biomechanical properties of single-strand and single-loop tibialis (anterior and posterior) tendon allografts. A comparison was made with bone-patellar tendon-bone (BPTB) allografts. Sixty-four tendon allografts were evaluated in this study. Sixteen of these were single-strand tibialis anterior (TA) and 16 single-strand tibialis posterior (TP) tendons. Sixteen single-loop TA and TP tendons were also tested. The fourth group was composed of 16 BPTB allografts. The biomechanical properties determined were maximal load, stiffness, cross-sectional area and elongation. The results of this study showed that the maximal load of the single-loop tibialis tendons (1,553 +/- 62 N) was greater than of the BPTB (1,139 +/- 99 N), TA (776 +/- 43 N) and TP (888 +/- 64 N) tendons. The stiffness of the single-loop tibialis tendons (236 +/- 10 N/mm) was also greater than of the BPTB (168 +/- 13 N/mm), TA (60 +/- 2 N/mm) and TP (73 +/- 5 N/mm) tendons. The cross-sectional area of the BPTB tendons was 67 +/- 5 mm(2), of the single-loop tibialis tendons 36 +/- 2 mm(2), of the TA tendons 20 +/- 1 mm(2), and of the TP tendons 23 +/- 1 mm(2). The elongation of the single-loop tibialis tendons and of the BPTB tendons was almost similar (7 +/- 0.4 mm). The same applied to the TA and TP tendons (14 +/- 0.6 mm). The results of this in vitro mechanical study suggest that fresh-frozen single-loop TA and TP tendons, and BPTB allografts are an acceptable substitute for hamstrings in anterior cruciate ligament reconstruction.

The addition of calcium ions to starch/Carbopol mixtures enhances the nasal bioavailability of insulin

To evaluate the influence of calcium poly(acrylates) on the nasal absorption of insulin in rabbits, starch/poly(acrylic acid) (ratio 25/75) (SD 25/75) was neutralised with NaOH and/or Ca(OH)(2). After neutralisation, a mixture of sodium and/or calcium carboxylate was formed depending on the Ca(OH)(2) concentration in the formulation. IR spectroscopy confirmed that most of the calcium molecules in the formulation interacted with acid groups of the acrylic acid polymer. Addition of Ca(OH)(2) to aqueous dispersions containing starch/poly(acrylic acid) yielded powders with an enhanced absorption of insulin after nasal delivery to rabbits in comparison with the equivalent powder without Ca(OH)(2). A mixture of SD 25/75 and Ca(OH)(2) at a ratio of 90/10 neutralised to pH 7.4 with NaOH induced the highest absorption of insulin, obtaining a bioavailability of +/-29% (vs. 19% for an equivalent formulation without Ca(OH)(2)). This increase in nasal delivery was possibly due to a higher elasticity after dispersing this formulation in nasal fluid and to a higher water absorbing capacity. Furthermore, after nasal delivery of (SD 25/75)/Ca(OH)(2) 90/10, a decrease in t(max) was observed, possibly due to a progressive dissociation of Ca(2+)-ions after hydration of the powder resulting in the closing of the tight junctions.

Outlier mining in high throughput screening experiments

A data mining procedure for the rapid scoring of high-throughput screening (HTS) compounds is presented. The method is particularly useful for monitoring the quality of HTS data and tracking outliers in automated pharmaceutical or agrochemical screening, thus providing more complete and thorough structure-activity relationship (SAR) information. The method is based on the utilization of the assumed relationship between the structure of the screened compounds and the biological activity on a given screen expressed on a binary scale. By means of a data mining method, a SAR description of the data is developed that assigns probabilities of being a hit to each compound of the screen. Then, an inconsistency score expressing the degree of deviation between the adequacy of the SAR description and the actual biological activity is computed. The inconsistency score enables the identification of potential outliers that can be primed for validation experiments. The approach is particularly useful for detecting false-negative outliers and for identifying SAR-compliant hit/nonhit borderline compounds, both of which are classes of compounds that can contribute substantially to the development and understanding of robust SARs. In a first implementation of the method, one- and two-dimensional descriptors are used for encoding molecular structure information and logistic regression for calculating hits/nonhits probability scores. The approach was validated on three data sets, the first one from a publicly available screening data set and the second and third from in-house HTS screening campaigns. Because of its simplicity, robustness, and accuracy, the procedure is suitable for automation.

The clinical significance of error measurement in the interpretation of treatment results

The aims of this investigation were to determine the errors involved in cephalometric landmark identification and to link these to the interpretation of treatment results. Fifty cephalograms were randomly selected from patient files and the following were determined. (i) Accuracy of the digitizer--single tracing digitized on five occasions on each of 10 different positions on the digitizer by one observer. (ii) Intra- and inter-observer digitizing error--35 landmarks on the same tracing (on a fixed position) digitized on five occasions by each of four judges. (iii) Intra- and inter-observer tracing error--five separate tracings of 10 different cephalograms by four judges. There were no significant differences in the variances of the co-ordinates for each landmark between the different positions on the digitizer (mean variance x-axis 0.07 mm and y-axis 0.08 mm). (ii) One-way ANOVA showed no significant intra- or inter-observer differences in digitation. (iii) Levene's test for homogeneity of variance showed significant differences in the co-ordinates of different landmarks and between the same landmarks on different cephalograms. Two-way ANOVA showed significant differences between observers for the same landmark that were greater than the intra-observer differences. The results indicate that tracing accuracy is a limiting factor in cephalometry. The variance of each landmark is dependent on the quality of the cephalogram. Inter-observer differences were greater than intra-observer effects and these were random, rather than systematic errors. Minimal error estimation calculations enable discrimination between treatment results and measurement errors.

The effect of tooth size discrepancy on occlusion: An experimental study

The purposes of this experimental study are the following: (1) to compare the anterior and overall tooth size ratios reported by Bolton to values reported in epidemiologic studies, (2) to assess the accuracy of tooth size discrepancy measurements, (3) to investigate to what extent generalized tooth size discrepancy affects occlusion, (4) to investigate the effect of leveling the curve of Spee, and (5) to evaluate the effect of extraction therapy of 4 premolars on occlusion. For the first part of the study, Bolton's mean anterior and overall tooth size ratio (as well as the extraction values) were compared with calculations derived from 4 publications reporting mean mesiodistal tooth width by using the t test (P </=.05). The second part of the study was carried out on a setup made from 1 dental cast of a male patient judged to have an ideal occlusion at the end of a nonextraction treatment. Our data reveal (1) no significant difference between the overall tooth size ratios of the Bolton values compared to 4 studies, but the anterior ratios were significantly different, (2) high reproducibility (99%) of tooth size discrepancy measurements, (3) that severe tooth size discrepancy affects the occlusion only a little, (4) that an excessive (6 mm) curve of Spee creates the poorest setup result, and (5) that extraction therapy only slightly affected the final occlusion. The effect of generalized tooth size discrepancy appears to be limited.

Dental wear in horses in relation to the microhardness of enamel and dentine

The microhardness of enamel, primary dentine and secondary dentine was determined in the incisor teeth of 39 horses of three different breeds, trotter horses, Belgian draft horses and Arab horses. Using a microhardness tester fitted with a Knoop diamond indenter, the overall Knoop Hardness Number was determined for each tissue, and the influence of breed and age on the hardness were evaluated. Enamel and secondary dentine were significantly harder in Arab horses than in trotters and Belgian draft horses, but there were no significant differences between draft horses and trotter horses in the hardness of their enamel and dentine.

The EASI project--improving the effectiveness and quality of image-guided surgery

In recent years, advances in computer technology and a significant increase in the accuracy of medical imaging have made it possible to develop systems that can assist the clinician in diagnosis, planning, and treatment. This paper deals with an area that is generally referred to as computer-assisted surgery, image-directed surgery, or image-guided surgery. We report the research, development, and clinical validation performed since January 1996 in the European Applications in Surgical Interventions (EASI) project, which is funded by the European Commission in their "4th Framework Telematics Applications for Health" program. The goal of this project is the improvement of the effectiveness and quality of image-guided neurosurgery of the brain and image-guided vascular surgery of abdominal aortic aneurysms, while at the same time reducing patient risks and overall cost. We have developed advanced prototype systems for preoperative surgical planning and intraoperative surgical navigation, and we have extensively clinically validated these systems. The prototype systems and the clinical validation results are described in this paper.

[Evaluation of the long-term release of fluorides from type II glass ionomer cements with conventional setting reactions]

As a part of a fundamental investigation on the fluoride release of glass ionomer cements (GIC), this study investigates the operator dependency of the fluoride release. In this respect the GIC fluoride release of a classical powder-liquid based system (Fuji II) and a capsule-based system (Fuji Cap II) in water during 14 days was determined on the hand of 5 specimens per formulation, made by 5 different operators. The data reveal that the variance on the fluoride release as well as the mean fluoride release at a given time are independent of the operator for both Fuji II and Fuji Cap II. In order to derive fundamental factors affecting the GIC fluoride release, the long-term fluoride release of 10 conventional setting type II GIC is investigated. In this respect the fluoride release profiles (FRP) of each of 5 cylindrical specimens (d = 6 mm, h = 3 mm) of Fuji II (FP), Fuji Cap II (FC), Miracle Mix (MM), Chemfil II (CP), Chemfil II in caps. (CC), Chelon-Fil (CF), Ketac-Fil (KF), Shofu II (SH), Chelon-Silver (CS) and Ketac-Silver (KS) were determined. The specimens were made according to the manufacturer's instruction and equilibrated at 37 degrees C in 25 mL distilled water up to 140 days. The water was regularly renewed and the fluoride concentration [F] of the equilibrated solution determined. A Multivariate Data Analysis of the [[F], t]-profiles on the basis of Principal Component Analysis (PCA) reveals that the FRP can be classified into 4 distinct groups: [CS,KS,FP]-[FC,CC]-[CF,KF] and [MM], leaving SH and CP apart as unclassifiable. When the cumulative amount of fluoride released ([F]c) for each individual sample is calculated and fitted as a function of time, a regression analysis shows that [F]c is most adequately fitted (r > 0.99) by [F]c = [F]I/t+t1/2 + beta, square root of t, indicating that 2 kinetic processes are responsible for the FRP. A comparison of the parameters of this equation ([F]I, t1/2 and beta) shows that the physicochemical rationale for this classification of the GIC conforms to differences in the kinetics of these processes. From the classification, it becomes apparent that different formulations can result in the same FRP.

Anaplastic (malignant) ganglioglioma arising from heterotopic grey matter nodules

Anaplastic ganglioglioma is a rare malignant neoplasm. The short clinical course and the anaplastic histological features are characteristics of malignant ganglioglioma. Immunohistochemistry is necessary for the final diagnosis. The MRI appearances are described here for the first time in literature. Nodular grey matter heterotopias had been demonstrated and the patient developed an anaplastic ganglioglioma two years later, on the same place where the grey matter heteropias had been seen. This finding supports the hypothesis that these tumours may arise from grey matter nodules.

An EPR study of intact and powdered human tooth enamel dried at 400 degrees C

An EPR study of human tooth enamel dried at 400 degrees C is presented. Enamel blocks as well as powdered samples were investigated. The discussion deals mainly with three different spectral components, i.e., a CO3(3-) and two different CO2- signals. Using the anisotropic enamel block spectra, a convincing differentiation between the latter two radicals was possible. The first CO2- signal shows no dependence on the orientation of the enamel blocks, disappears from the spectrum upon heating, and was assigned to a surface radical. The second CO2- component is mainly responsible for the angular variation of the enamel blocks and is assigned to a bulk position. For the CO3(3-) ion, the (pseudo) angular variation of its isolated spectrum is presented and discussed. By means of the results presented in this study, earlier interpretation problems are considerably reduced.

The use of magnetic resonance angiography in stereotactic neurosurgery

The authors discuss the advantages and disadvantages of the use of magnetic resonance (MR) angiography images in stereotactic neurosurgery. Current computer programs designed to assist the neurosurgeon in the planning of stereotactic neurosurgical interventions use intraarterial digital subtraction angiography images to visualize the blood vessels. Magnetic resonance angiography is a recent technique with a number of advantages over the digital subtraction method: it is less invasive and less prone to complications; it provides truly three-dimensional data sets that can be viewed from any direction; and it can visualize both stationary and flowing tissues with the same imaging device and localizer frame. Although digital subtraction images are still superior in contrast and vascular detail, state-of-the-art high-resolution MR angiography sequences provide sufficient vascular detail for planning surgery. Contrast-enhanced MR angiography images were acquired using adapted gradient-echo sequences to compensate for flow-induced distortions; postacquisition distortion correction was not necessary. Five methods to integrate and inspect a possible trajectory in the MR angiography data are discussed. Initial clinical experience with eight patients led to the conclusion that MR angiography is a valuable imaging modality that can be integrated reliably into a stereotactic neurosurgery planning procedure.

Protocol for the clinical functionality assessment of a workstation for stereotactic neurosurgery

The objective of this study is to establish a protocol for the technical and clinical evaluation of a workstation for the planning of stereotactic neurosurgical interventions that has been developed in the framework of a joint European research project. Although several such workstations have been proposed before, they lacked the final and most important step, that of clinical validation. They failed to rigorously prove that their product was useful. The authors present a new method that is applicable to the evaluation of a wide range of medical technologies. Their protocol basically assesses the clinical relevance of the user requirements that are at the root of the development of the new technology. The evaluation consists of two stages. During functional specification, iterative prototyping is used to establish the clinical requirements and to assure the quality of the final product. A case study design is used in a second stage that assesses the clinical usability. A before-after study gives a first indication of cost effectiveness and improvement of health care quality.

Chemolysis of calcium containing urinary calculi. A review

A review of current literature and research on chemolysis of calcium containing urinary stones is made. The type of chemolytic solution is dependent upon the composition of the stone. Calcium phosphates can be desolved with Suby or Renadecin solution although it is often tedious and time consuming procedure. Calcium oxalate, the major urinary stone component, can not be dissolved by these solutions. EDTA and other strong calcium chelators cannot be used because of their local toxicity. Certain enzymes can digest the organic matrix of the stone. The indication to chemolysis of stones are rather restricted.

How does the stereotactic workstation help the neurosurgeon?

At the KUL University of Leuven a workstation for the planning of neurosurgical stereotactic procedures has been developed. Its benefits are illustrated in three exemplary cases. The CT and/or MR images, acquired under stereotactic conditions, are transmitted via a PACS network (picture archiving and communication systems) directly to the stereotactic workstation in the operating theater. Target and entry point can be accurately defined on zoomed images. The trajectory can be checked and modified on all registered data sets and on resliced images along any plane. Maximum intensity projection of magnetic resonance angiography data sets along any arbitrary direction show the relative position of the blood vessels and the trajectory. During the preceding 32 months 29 patients were operated on using the stereotactic workstation. Postoperatively no new neurological deficit was observed in any of these patients. The workstation improves patient safety and increases the accuracy of neurosurgical stereotactic operations, because it helps the neurosurgeon to avoid blood vessels and/or important functional areas.

Isolation and identification by FAB mass spectrometry and NMR spectroscopy of a demethylated metabolite of FK506 from erythromycin-induced rabbit liver microsomes

A new demethylated metabolite, extracted from erythromycin-induced rabbit liver microsomes incubation media, isolated by HPLC and identified by FAB/MS and NMR, is described. Moreover, NMR spectra suggest the existence of tautomeric forms of this O-demethylated metabolite of FK506.

Watertight sutures with fibrin glue: an experimental study

A rat model was developed to test the watertightness of sutures and used to evaluate the value of fibrin glue (Tissucol, Immuno France, Tisseel, Immuno U.S., Inc.) in making conventional sutures watertight. Fibrin glue raised the mean hydrostatic pressure to which the skin suture resisted from 9.1 to 26.3 cm H2O, thus indicating that it enhances suture watertightness immediately after surgery. After 3 and 6 days, the pressure was increased, respectively, from 24.8 to 47.9 and from 56.5 to 73.3 cm H2O. For bladder sutures, the results are comparable.

Rationale for local toxicity of calcium chelators

Calcium chelating agents, such as ethylenediaminetetraacetate are toxic to urothelium. Their capacity to form complexes with calcium ions, which is the basis for their chemolytical effectiveness, also determines their toxicity. A decrease of chemolytical effectiveness by prior saturation of the chelator with Ca2+ or by lowering the pH to levels unfavourable for calcium binding significantly diminishes tissue injury. Exchange of Mg2+ ions does not, however, diminish tissue damage. The clinical use of calcium ligands is therefore unsafe.

Toxicity to the urothelium of calcium chelating agents for chemolysis

Solutions, based on calcium chelating agents, with excellent prospects as litholytic agents in vitro were tested on toxicity to the mucosa of the bladder of the rat. The following compounds were tested at a concentration of 12.5 mM., buffered with triethanolamine 0.2 M at pH 8 and 8.5: ethylenediaminetetra acetic acid with as cation H2+, Li+, Na+, K+, and Cs+, trans-cyclohexane-1.2 diaminetetra acetic acid (cations H+, Na+, K+), diethylenetriamine penta acetate (cations H+, Na+, K+), disodiumethyleneglycol-bis (2 aminoethyl) tetra acetic acid and disodium hydroxyethylethylenediamine tetra acetate. All agents were found to be very noxious to the bladder mucosa of the rat and are unlikely to be safe for clinical use.

Toxicity of litholytic ethylenediaminetetraacetic acid solutions to the urothelium of the rat and dog

The toxicity to the urothelium of bipotassium ethylene-diaminetetraacetic acid (K2-EDTA) buffered with 0.2 M triethanolamine (TEA) at pH 8 and 8.5 was tested in rats and dogs. Even at a low concentration of 3.125 mM, K2-EDTA is very noxious to the bladder mucosa. This toxicity is not due to the buffer TEA, which is well tolerated. Although buffered K2-EDTA, at pH 8.5 is an excellent chemolytic agent for calcium-containing stones, its clinical use is limited by this toxicity.

Effect of aluminum hydroxide on diflunisal absorption

1 The effect of aluminum hydroxide on the oral absorption of diflunisal was studied in healthy subjects. 2 Relative bioavailability of the oral diflunisal dose (500 mg) was estimated by comparison of the areas under plasma concentration versus time curves, and comparison of the amount of drug (unchanged + glucuronides) excreted in the urine. 3 From the AUC-method, a relative bioavailability of 0.60 was calculated. A similar value (F = 0.63) was obtained from the urinary excretion data. 4 The results indicate that co-administration of aluminum hydroxide reduces the bioavailability of oral diflusinal by about 40%.

Biotransformation of diflunisal and renal excretion of its glucuronides in renal insufficiency

1 A single oral dose of 500 mg diflunisal was administered to control subjects and patients with varying degrees of renal insufficiency to estimate the disposition kinetics of this drug.

2 Diflunisal and the sum of its ester and ether glucuronides conjugates were measured fluorimetrically.

3 In normals terminal plasma half-lives (T_½β) of diflunisal and its glucuronides were very similar: 10.8 h and 11.8 h respectively. The finding that plasma half-life was shortened with declining diflunisal plasma levels suggests capacity-limited elimination.

4 In subjects with normal renal function 78.6 ± 2.7% of the administered dose was recovered in 72 h urine, mainly as the glucuronide conjugates.

5 With increasing degree of renal function impairment T_½β of diflunisal was progressively prolonged up to ten times normal probably due to slowed biotransformation. This was associated with increasing retention of the conjugated metabolites in plasma due to marked reduction of the urinary excretion of the glucuronide conjugates.

6 The apparent volume of distribution of diflunisal was very small in normals (7.3 ± 0.4 l) and was significantly increased in patients with renal insufficiency (up to 16.2 ± 2.2 l).

7 Diflunisal elimination studies performed during haemodialysis did not reveal any significant change in diflunisal plasma half-time. In vivo ultrafiltration studies during haemodialysis have shown that diflunisal is 98-99% plasma protein bound in uraemic patients.

8 The present study indicates that although diflunisal is primarily eliminated by biotransformation, T_½β is prolonged in renal insufficiency and dose adjustment will accordingly be required in patients with renal function impairment.

The effect of end-stage renal failure and haemodialysis on the elimination kinetics of sotalol

A single oral dose of sotalol (160 mg) was administered to control subjects with normal renal function and patients with chronic renal failure in the interdialysis period to estimate the elimination kinetics of the drug. Sotalol concentrations in body fluids were measured fluorimetrically using a modified Garrett and Schnelle (1971) method. Mean plasma half-life (T 1/2) was approximately 5 h in normals, 42 h in patients off-dialysis. During haemodialysis the mean plasma half-time was on the average 7 hours. Comulative urinary excretion of the drug was considerably lower in the patient group: 9% of the dose in 48 h as opposed to 61% in normals. Comparison of sotalol concentrations in plasma versus ultrafiltrate from the coil kidney indicates that the drug in vivo is negligible bound to plasma proteins in remal patients. The net-lowering effect of a 6 to 7 h haemodialysis on the plasma concentration decay line was by 20%. Post-dialysis plasma concentration data suggest that the rate at which sotalol returns to plasma from body tissues appears to be the rate-controlling factor in the elimination of sotalol by haemodialysis.

Influence of the hemodialysis on the half-life of practolol in patients with severe renal failure

Practolol, a recent and more selective beta-adrenergic receptor blocking drug, was given orally as a single dose of 200 mg to seven healthy volunteers and to six patients suffering from severe renal impairment and submitted to the long-term hemodialysis program. The plasma drug decay was markedly slowed and the plasma half-life was prolonged sixfold in the uremic patients in comparison to healthy volunteers. Hemodialysis (8 hours) starting 48 hours after drug intake lowered plasma practolol significantly but transiently. The shorter half-life during hemodialysis and the detection of equally high values of practolol in the ultrafiltrates as in the plasma demonstrate that this drug is readily removable from the plasma. However, the ascending slope of the plasma drug concentration curve which appeared following hemodialysis is suggestive of an incomplete drug removal from the body.