A review of the off-label use of selamectin (Stronghold<Superscript>®</Superscript>/Revolution<Superscript>®</Superscript>) in dogs and cats

Since its introduction approximately seven years ago, selamectin (Stronghold^®/Revolution^®, Pfizer Inc.) has been used off-label to treat a number of ecto- and endoparasite conditions in dogs and cats. It has been used as a successful prophylactic against Dirofilaria repens and as a treatment for Aelurostrongylus abstrusus in cats. It has also been used to treat notoedric mange, infestation with the nasal mite Pneumonyssoides caninum, Cheyletiella spp. and Neotrombicula autumnalis infestations and larval Cordylobia anthropophaga infection. However, to date attempts to treat generalised canine demodicosis have not been successful. In all cases, treatment was apparently well tolerated by the host.     

Accuracy of the StressEraser<Superscript>®</Superscript> in the Detection of Cardiac Rhythms

StressEraser is a commercially marketed biofeedback device designed to enhance heart rate variability. StressEraser makes its internal calculations on beat-to-beat measures of finger pulse intervals. However, the accuracy and precision of StressEraser in quantifying interbeat intervals using finger pulse intervals has not been evaluated against standard laboratory equipment using R-R intervals. Accuracy was assessed by simultaneously recording interbeat intervals using StressEraser and a standard laboratory ECG system. The interbeat intervals were highly correlated between the systems. The average deviation in interbeat interval recordings between the systems was approximately 6 ms. Moreover, correlations approached unity between the systems on estimates of heart period, heart rate, and heart rate variability. Feedback from StressEraser is based on an interbeat time series that provides sufficient information to provide an excellent estimate of the dynamic changes in heart rate and heart rate variability. The slight variations between StressEraser and the laboratory equipment in quantifying heart rate and heart rate variability are due to features related to monitoring heart rate with finger pulse: (1) a lack in precision in the peak of the finger pulse relative to the clearly defined inflection point in the R-wave, and (2) contribution of variations in pulse transit time.     

The Antioxidant and Antigenotoxic Effects of Pycnogenol<Superscript>®</Superscript> on Rats Treated With Cisplatin

Oxidative stress and inflammation are implicated in the pathogenesis of cisplatin-induced toxicity. Pycnogenol® is known for its strong antioxidant and anti-inflammatory effects. In this study, the possible protective effects of pycnogenol on kidney, bone marrow, and red blood cells in rats treated with cisplatin were investigated. The rats were divided into four groups. Group 1 was the control and groups 2, 3, and 4 were orally treated with pycnogenol (200 mg/kg bw, o.p) for 5 days, treated with cisplatin (7 mg/kg bw, i.p.) on the fifth day and treated with cisplatin plus pycnogenol, respectively. Antioxidative parameters in kidney and red blood cells were measured. Chromosome anomalies in bone marrow and renal histopathology were also investigated. Activities of pro-oxidant enzymes (myeloperoxidase and xanthine oxidase), malondialdehyde, and nitric oxide levels significantly increased but antioxidant enzymes activities decreased in the kidneys and red blood cells after cisplatin treatment. Pycnogenol treatment prior to the administration of cisplatin significantly decreased cisplatin-induced injury, as evidenced by its normalizing these parameters. Chromosomal aberrations decreased and mitotic index frequencies increased in bone marrow treated with cisplatin plus pycnogenol. These findings suggest that pycnogenol may be a useful protective agent against the toxicity associated with cisplatin therapy.     

The Algae Foundation<Superscript>®</Superscript> and algal-based education initiatives

The Algae Foundation^®, an American non-profit organization formed in February 2013, is developing a rich portfolio of algal-based Science, Technology, Engineering and Math (STEM) initiatives. The Algae Foundation’s efforts include the following: (1) formation of the Algae Technology Educational Consortium (ATEC); (2) development of two community college degrees: (i) Algal Biology and Cultivation and (ii) Algal Biotechnology; (3) development of the Algae Cultivation Extension Short-courses (ACES); (4) kindergarten to 12th grade (K–12) algal-based STEM curriculum initiatives; (5) student scholarships; and (6) funding of the revision of the Industrial Algae Measurements publication. The Algae Foundation^® has been supported by more than 50 volunteers dedicating their time and intellectual capital to achieving its stated goals. The ATEC effort has initiated its first degree program in Algal Biology and Cultivation at Santa Fe Community College (SFCC), New Mexico, USA, in the Fall 2016 semester. The Algal Biotechnology degree program is scheduled to start in the Fall 2017 semester at Austin Community College (ACC), Texas, USA. A K–12 algal-based STEM initiative completed its pilot debut at the Aviara Oaks Middle School, Carlsbad, California, USA, in Spring 2016. The expansion of the algal curriculum K–12 program will reach 50 schools in 2017 to be followed by a national rollout in 2018.     

Simple generation of site-directed point mutations in the <Emphasis Type="Italic">Escherichia coli</Emphasis> chromosome using Red<Superscript>®</Superscript>/ET<Superscript>®</Superscript> Recombination

Background  

Introducing point mutations into bacterial chromosomes is important for further progress in studies relying on functional genomics, systems- and synthetic biology, and for metabolic engineering. For many investigations, chromosomal systems are required rather than artificial plasmid based systems.     

Pharmacokinetic comparability of Prolastin<Superscript>®</Superscript>-C to Prolastin<Superscript>®</Superscript> in alpha<Subscript>1</Subscript>-antitrypsin deficiency: a randomized study

Background

Alpha₁-antitrypsin (AAT) deficiency is characterized by low blood levels of alpha₁-proteinase inhibitor (alpha₁-PI) and may lead to emphysema. Alpha₁-PI protects pulmonary tissue from damage caused by the action of proteolytic enzymes. Augmentation therapy with Prolastin^® (Alpha₁-Proteinase Inhibitor [Human]) to increase the levels of alpha₁-PI has been used to treat individuals with AAT deficiency for over 20 years. Modifications to the Prolastin manufacturing process, incorporating additional purification and pathogen-reduction steps, have led to the development of an alpha₁-PI product, designated Prolastin^®-C (Alpha₁-Proteinase inhibitor [Human]). The pharmacokinetic comparability of Prolastin-C to Prolastin was assessed in subjects with AAT deficiency.

Methods

In total, 24 subjects were randomized to receive 60 mg/kg of functionally active Prolastin-C or Prolastin by weekly intravenous infusion for 8 weeks before crossover to the alternate treatment for another 8 weeks. Pharmacokinetic plasma samples were drawn over 7 days following last dose in the first treatment period and over 10 days following the last dose in the second period. The primary end point for pharmacokinetic comparability was area under the plasma concentration versus time curve over 7 days post dose (AUC_{0-7 days}) of alpha₁-PI determined by potency (functional activity) assay. The crossover phase was followed by an 8-week open-label treatment phase with Prolastin-C only.

Results

Mean AUC_{0-7 days} was 155.9 versus 152.4 mg*h/mL for Prolastin-C and Prolastin, respectively. The geometric least squares mean ratio of AUC_{0-7 days} for Prolastin-C versus Prolastin had a point estimate of 1.03 and a 90% confidence interval of 0.97-1.09, demonstrating pharmacokinetic equivalence between the 2 products. Adverse events were similar for both treatments and occurred at a rate of 0.117 and 0.078 per infusion for Prolastin-C (double-blind treatment phase only) and Prolastin, respectively (p = 0.744). There were no treatment-emergent viral infections in any subject for human immunodeficiency virus, hepatitis B or C, or parvovirus B19 during the course of the study.

Conclusion

Prolastin-C demonstrated pharmacokinetic equivalence and a comparable safety profile to Prolastin.

Trial Registration

ClinicalTrials.gov Identifier: NCT00295061

     

Comparison of Alexa Fluor<Superscript>®</Superscript> and CyDye<Superscript>™</Superscript> for practical DNA microarray use

Microarrays are a powerful tool for comparison and understanding of gene expression levels in healthy and diseased states. The method relies upon the assumption that signals from microarray features are a reflection of relative gene expression levels of the cell types under investigation. It has previously been reported that the classical fluorescent dyes used for microarray technology, Cy3 and Cy5, are not ideal due to the decreased stability and fluorescence intensity of the Cy5 dye relative to the Cy3, such that dye bias is an accepted phenomena necessitating dye swap experimental protocols and analysis of differential dye affects. The incentive to find new fluorophores is based on alleviating the problem of dye bias through synonymous performance between counterpart dyes. Alexa Fluor 555 and Alexa Fluor 647 are increasingly promoted as replacements for CyDye in microarray experiments. Performance relates to the molecular and steric similarities, which will vary for each new pair of dyes as well as the spectral integrity for the specific application required. Comparative analysis of the performance of these two competitive dye pairs in practical microarray applications is warranted towards this end. The findings of our study showed that both dye pairs were comparable but that conventional CyDye resulted in significantly higher signal intensities (P < 0.05) and signal minus background levels (P < 0.05) with no significant difference in background values (P > 0.05). This translated to greater levels of differential gene expression with CyDye than with the Alexa Fluor counterparts. However, CyDye fluorophores and in particular Cy5, were found to be less photostable over time and following repeated scans in microarray experiments. These results suggest that precautions against potential dye affects will continue to be necessary and that no one dye pair negates this need.     

Effect of different methods of Ca<Superscript>2+</Superscript> extraction from PSII oxygen-evolving complex on the Q<Subscript>A</Subscript><Superscript>−</Superscript> oxidation kinetics

Lumenal extrinsic proteins PsbO, PsbP, and PsbQ of photosystem II (PSII) protect the catalytic cluster Mn₄CaO₅ of oxygen-evolving complex (OEC) from the bulk solution and from soluble compounds in the surrounding medium. Extraction of PsbP and PsbQ proteins by NaCl-washing together with chelator EGTA is followed also by the depletion of Ca²⁺ cation from OEC. In this study, the effects of PsbP and PsbQ proteins, as well as Ca²⁺ extraction from OEC on the kinetics of the reduced primary electron acceptor (Q_A ^?) oxidation, have been studied by fluorescence decay kinetics measurements in PSII membrane fragments. We found that in addition to the impairment of OEC, removal of PsbP and PsbQ significantly slows the rate of electron transfer from Q_A ^? to the secondary quinone acceptor Q_B. Electron transfer from Q_A ^? to Q_B in photosystem II membranes with an occupied Q_B site was slowed down by a factor of 8. However, addition of EGTA or CaCl₂ to NaCl-washed PSII did not change the kinetics of fluorescence decay. Moreover, the kinetics of Q_A ^? oxidation by Q_B in Ca-depleted PSII membranes obtained by treatment with citrate buffer at pH 3.0 (such treatment keeps all extrinsic proteins in PSII but extracts Ca²⁺ from OEC) was not changed. The results obtained indicate that the effect of NaCl-washing on the Q_A ^? to Q_B electron transport is due to PsbP and PsbQ extrinsic proteins extraction, but not due to Ca²⁺ depletion.     

Efficacy of the new repellent BioUD<Superscript>®</Superscript> against three species of ixodid ticks

BioUD ^® with the active ingredient 2-undecanone originally derived from wild tomato plants is a new repellent recently registered by the US EPA. Repellent efficacy of BioUD ^® (7.75% 2-undecanone) and DEET (98.11%) was examined in the laboratory using a choice test between repellent-treated and control filter paper surfaces for Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis. BioUD ^® provided greater repellency against A. americanum and I. scapularis than DEET. No difference was found between BioUD ^® and DEET against D. variabilis. In head-to-head assays between BioUD ^® and DEET, undiluted and 50% dilutions of BioUD^® were more repellent than undiluted DEET against all three species tested. Similarly, a 25% dilution of BioUD^® was more repellent than DEET against A. americanum while no difference in mean percentage repellency was found between a 25% dilution of BioUD^® and DEET against I. scapularis. Based on regression analysis, the concentration of BioUD^® required for equivalent repellency to 98.11% DEET was 39.5% for D. variabilis and 29.7% for I. scapularis. A log-probit model could not be constructed for A. americanum from the dosages tested. Based on filter paper head-to-head assays, BioUD^® is at least 2–4 times more active as a repellent than DEET against three species of ixodid ticks under the conditions of our laboratory bioassays.     

Determination of the lifetime of D<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> and HD<Superscript>−</Superscript> ions

A method for determining the lifetime of unstable ions is described. The method is based on measuring the decrease in the ion beam current onto a fixed detector with increasing path length of the ion beam from the ion source to the detector. The measurements performed for D^? ₂ and HD^? molecular ions have shown that their lifetimes are 3.5 ± 0.1 and 4.4 ± 0.1 μs, respectively.     

Tolerability and efficacy of the intestinal phosphate binder Lantharenol<Superscript>®</Superscript> in cats

Background

Tolerability and efficacy of the intestinal phosphate binder Lantharenol^® (lanthanum carbonate octahydrate) were tested in two prospective, randomized and negative controlled laboratory studies with healthy adult cats fed commercial maintenance diets non-restricted in phosphorus. In the first study, the maximal tolerated dose was determined. Starting from a dose of 0.125 g/kg body weight mixed with the daily feed ration, the dose of Lantharenol^® was doubled every other week until signs of intolerability were observed (N = 10 cats compared to 5 untreated controls). In the second study, the effects of feed supplementation for two weeks with approximately 2, 6, and 20% of the maximal tolerated dose on phosphorus excretion patterns and balance were assessed (N = 8 cats per group).

Results

Lantharenol^® was found to be safe and well tolerated up to the dose of 1 g/kg bodyweight, corresponding to a concentration of 84 g Lantharenol^®/kg complete feed, defined as dry matter with a standard moisture content of 12%. Feed supplementation for two weeks with approximately 2-20% of this dosage (i.e., 1.6, 4.8, and 16 g/kg complete feed) resulted in a shift from urinary to faecal phosphorus excretion. Apparent phosphorus digestibility was dose-dependently reduced compared to the control group fed with diet only (N = 8).

Conclusions

The feed additive was well accepted and tolerated by all cats. Therefore, Lantharenol^® presents a well tolerated and efficacious option to individually tailor restriction of dietary phosphorus as indicated, for instance, in feline chronic kidney disease.

     

A Voltage-Dependent Ca<Superscript>2+</Superscript> Influx Pathway Regulates the Ca<Superscript>2+</Superscript>-Dependent Cl<Superscript>−</Superscript> Conductance of Renal IMCD-3 Cells

We have previously shown that the membrane conductance of mIMCD-3 cells at a holding potential of 0 mV is dominated by a Ca²⁺-dependent Cl⁻ current (I_CLCA). Here we report that I_CLCA activity is also voltage dependent and that this dependence on voltage is linked to the opening of a novel Al³⁺-sensitive, voltage-dependent, Ca²⁺ influx pathway. Using whole-cell patch-clamp recordings at a physiological holding potential (−60 mV), I_CLCA was found to be inactive and resting currents were predominantly K⁺ selective. However, membrane depolarization to 0 mV resulted in a slow, sigmoidal, activation of I_CLCA (T _0.5 ~ 500 s), while repolarization in turn resulted in a monoexponential decay in I_CLCA (T _0.5 ~ 100 s). The activation of I_CLCA by depolarization was reduced by lowering extracellular Ca²⁺ and completely inhibited by buffering cytosolic Ca²⁺ with EGTA, suggesting a role for Ca²⁺ influx in the activation of I_CLCA. However, raising bulk cytosolic Ca²⁺ at −60 mV did not produce sustained I_CLCA activity. Therefore I_CLCA is dependent on both an increase in intracellular Ca²⁺ and depolarization to be active. We further show that membrane depolarization is coupled to opening of a Ca²⁺ influx pathway that displays equal permeability to Ca²⁺ and Ba²⁺ ions and that is blocked by extracellular Al³⁺ and La³⁺. Furthermore, Al³⁺ completely and reversibly inhibited depolarization-induced activation of I_CLCA, thereby directly linking Ca²⁺ influx to activation of I_CLCA. We speculate that during sustained membrane depolarization, calcium influx activates I_CLCA which functions to modulate NaCl transport across the apical membrane of IMCD cells.     

Estimation of denitrification potential in a karst aquifer using the <Superscript>15</Superscript>N and <Superscript>18</Superscript>O isotopes of NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>

A confined aquifer in the Malm Karst of the Franconian Alb, South Germany was investigated in order to understand the role of the vadose zone in denitrifiaction processes. The concentrations of chemical tracers Sr²⁺ and Cl^– and concentrations of stable isotope ¹⁸O were measured in spring water and precipitation during storm events. Based on these measurements a conceptual model for runoff was constructed. The results indicate that pre-event water, already stored in the system at the beginning of the event, flows downslope on vertical and lateral preferential flow paths. Chemical tracers used in a mixing model for hydrograph separation have shown that the pre-event water contribution is up to 30%. Applying this information to a conceptual runoff generation model, the values of ¹⁵N and ¹⁸O in nitrate could be calculated. Field observations showed the occurence of significant microbial denitrification processes above the soil/bedrock interface before nitrate percolates through to the deeper horizon of the vadose zone. The source of nitrate could be determined and denitrification processes were calculated. Assuming that the nitrate reduction follows a Rayleigh process one could approximate a nitrate input concentration of about 170 mg/l and a residual nitrate concentration of only about 15%. The results of the chemical and isotopic tracers postulate fertilizers as nitrate source with some influence of atmospheric nitrate. The combined application of hydrograph separation and determination of isotope values in ¹⁵N and ¹⁸O of nitrate lead to an improved understanding of microbial processes (nitrification, denitrification) in dynamic systems.     

Identification of CD133<Superscript>−</Superscript>/Telomerase<Superscript>low</Superscript> Progenitor Cells in Glioblastoma-Derived Cancer Stem Cell Lines

Glioblastoma multiforme (GBM) is paradigmatic for the investigation of cancer stem cells (CSC) in solid tumors. The CSC hypothesis implies that tumors are maintained by a rare subpopulation of CSC that gives rise to rapidly proliferating progenitor cells. Although the presence of progenitor cells is crucial for the CSC hypothesis, progenitor cells derived from GBM CSC are yet uncharacterized. We analyzed human CD133⁺ CSC lines that were directly derived from CD133⁺ primary astrocytic GBM. In these CSC lines, CD133⁺/telomerase^high CSC give rise to non-tumorigenic, CD133⁻/telomerase^low progenitor cells. The proliferation of the progenitor cell population results in significant telomere shortening as compared to the CD133⁺ compartment comprising CSC. The average difference in telomere length as determined by a modified multi-color flow fluorescent in situ hybridization was 320 bp corresponding to 4–8 cell divisions. Taken together, we demonstrate that CD133⁺ primary astrocytic GBM comprise proliferating, CD133⁻/telomerase^low progenitor cell population characterized by low telomerase activity and shortened telomeres as compared to CSC.     

Effect of Lead Ion on the Function of the Human Ether-À-Go-Go-Related Gene K<Superscript>+</Superscript> Channel

Lead (Pb) is a trace metal element in the human body. In order to understand the hazard mechanism of the elevated blood lead level on the human body, the effect of Pb²⁺ on the human ether-à-go-go-related gene (hERG) K⁺ channel in the HEK 293 cell was investigated for the first time using whole-cell patch clamp technique, molecular dynamics simulation, and quantum chemistry calculation methods. We found that Pb²⁺ obviously inhibits the current of the hERG K⁺ channel, and delays the “activation” and “deactivation” of the hERG K⁺ channel, indicating that Pb²⁺ evidently decreases the function of the K⁺ channel in the cell. The effect is increased with increasing the concentration of Pb²⁺. When the concentration of Pb²⁺ is 400 μg L⁻¹, the function of the K⁺ channel is entirely lost. The results from the molecular dynamics simulation and quantum chemistry calculation indicated that Pb²⁺ can coordinate with the oxygen/sulfur atoms in the K⁺ channel protein, leading to the decrease in the function of the K⁺ channel. According to the experimental results, we suggested that once the K⁺ channel in the human body was irreversibly inactivated by Pb²⁺, it would affect the treatment and prognosis of Pb²⁺ intoxication.     

Effect of culture container and carbohydrate content on in vitro slow growth storage of the cherry rootstock ‘Gisela<Superscript>®</Superscript>5’

The present study investigated the effects of gas-tight and gas-permeable culture containers and different sucrose concentrations, as well as sucrose and mannitol combinations on the development of an effective in vitro slow growth storage protocol (at 4 °C, in darkness) for ‘Gisela^®5’ shoot cultures. ‘Gisela^®5’ is the most widely used cherry rootstock in Europe. This dwarf triploid hybrid has many advantages over the conventional cherry rootstocks. Optimizations for the cold storage of ‘Gisela^®5’ in vitro shoot cultures included use of storage medium supplemented with 10, 20, 30, 45, and 60 g L^?1 sucrose and sucrose (15, 30 g L^?1) and mannitol (15 g L^?1) combinations, contained in gas-tight glass jars and gas-permeable ‘Star Pac?’ bags. Cold storage was prolonged to 12 months, during which in every 3 months, cultures were evaluated. Possibility of 16 month-cold storage in gas-tight glass jars was also explored, during which gas chromatographic analysis was performed for the detection of CO₂ and ethylene accumulation for the first 5 months of cold storage. Our results showed that both the 12- and 16-month conservations were possible, especially when 45 or 60 g L^?1 sucrose was supplemented to storage medium, contained in glass jars. Mannitol inclusion to the storage medium was also effective to reduce the metabolic activity of the shoot cultures during storage; however, it did not have a significant positive influence on shoot quality in post-conservation.     

Toxicological evaluation of genetically modified cotton (Bollgard<Superscript>®</Superscript>) and Dipel<Superscript>®</Superscript> WP on the non-target soil mite <Emphasis Type="Italic">Scheloribates praeincisus</Emphasis> (Acari: Oribatida)

Insecticides derived from the bacterium Bacillus thuringiensis (Bt) and plants genetically modified (GM) to express B. thuringiensis toxins are important alternatives for insect pest control worldwide. Risk assessment of B. thuringiensis toxins to non-target organisms has been extensively studied but few toxicological tests have considered soil invertebrates. Oribatid mites are one of the most diverse and abundant arthropod groups in the upper layers of soil and litter in natural and agricultural systems. These mites are exposed to the toxic compounds of GM crops or pesticides mainly when they feed on vegetal products incorporated in the soil. Although some effects of B. thuringiensis products on Acari have been reported, effects on oribatid mites are still unknown. This study investigated the effects of the ingestion of Bt cotton Bollgard and of the B. thuringiensis commercial product Dipel WP on the pantropical species Scheloribates praeincisus (Scheloribatidae). Ingestion of Bollgard and Dipel did not affect adult and immature survivorship and food consumption (estimated by number of fecal pellets produced daily) or developmental time of immature stages of S. praeincisus. These results indicate the safety of Bollgard and Dipel to S. praeincisus under field conditions where exposition is lower and other food sources besides leaves of Bt plants are available. The method for toxicological tests described here can be adapted to other species of Oribatida, consisting on a new option to risk assessment studies.     

YUPI<Superscript>®</Superscript>, a regional footprint calculator

Purpose

Many tools to quantify the environmental impact of human decisions have been developed, but all of them seem to have a limited application at the regional or local level. A free-of-charge, Argentina-based personal footprint calculator software (YUPI^®) has been developed in order to raise awareness among local citizens about the environmental impacts generated by their daily habits. The extensive use of the tool will generate information suitable for future scientific studies based on local data.

Methods

The software calculates the ecological, carbon, and water footprints of individuals, implementing specific regional data from Argentina developed by the CLIOPE group, complemented with data from the Water Footprint Network and the Global Footprint Network. The calculator was developed focusing on interface attractiveness, ease of use, language simplicity, and a good trade-off between completion time and fullness.

Results and discussion

The YUPI^® software allows its users to understand at a glance their contribution to the environmental impacts of modern society and to quantify the reduction opportunities they have at hand. The program’s language and variables reflect local lifestyle choices, making the filling process accessible for children. The calculator was placed online as an educational tool for teachers and students from all educational levels, and it was also used by visitors in local science and educational fairs. Valuable data was collected for future initiatives on impact mitigation.

Conclusions

Amplified by the mass media, the new tool has helped raise awareness and discussion about the individual environmental footprint, both in the educational and in the domestic terrain. The strategy of creating a simple, easily administered, and widely available quiz helped bridge the gap between the academy and the people, making available to them the continuously updated information generated by the research groups. This is facilitating citizen not only to understand the complexity of the environmental problems but also to take informed actions leading to their mitigation.

     

Investigation into the Dissolution Rate Increase on Storage of Wellbutrin SR<Superscript>®</Superscript> 100 mg Tablets

The Food and Drug Administration (FDA) approved the New Drug Application for Wellbutrin sustained release (SR) 100 mg tablets on October 4, 1996. However, by 1998, the FDA expressed concern about the stability of this drug product based on an increase in the dissolution profile on storage. Data submitted in the annual report showed that this drug product could not meet the expiry of 18 months at the International Committee on Harmonization storage condition of 25°C/60% relative humidity. The FDA mandated a 12-month expiry and GlaxoWellcome tightened this further by instituting an expiry of 9 months. The FDA also requested a long-term solution to the stability of Wellbutrin SR 100 mg tablets. Investigations via colloidal solutions revealed that the dissolution rate increase on storage occurred due to acid hydrolysis of the release controlling polymer. This drug product was successfully reformulated by slowing the initial dissolution rate and having an increased ratio of release controlling polymer to acid stabilizer. The reformulation used the same ingredients and manufacturing unit processes as the original formulation. The reformulated drug product was approved by the FDA on October 11, 2000 with an 18-month shelf-life. The shelf-life was extended to 36 months in an annual update to the FDA on December 1, 2005.     

The role of phosphate on Omniscan<Superscript>®</Superscript> dechelation: an in vitro relaxivity study at pH 7

Nephrogenic systemic fibrosis (NSF), a disease occurring in patients with severe renal failure, may be linked to injections of gadolinium chelates, contrast agents used for magnetic resonance imaging. A hypothesis frequently proposed to explain NSF is dissociation of Gd³⁺ from its chelate, possibly from a deep storage compartment. Numerous in vivo and in vitro studies have been performed in an attempt to determine the extent of this dechelation and to understand its mechanism. Proton-assisted dechelation and transmetallation are the most widely described mechanisms of dechelation. This study investigated the possible ligand exchange role played by phosphate in the dechelation mechanism. Omniscan^® dechelation was monitored in vitro by relaxivity measurements performed at physiological pH with different concentrations of phosphate buffer and in the presence of endogenous cations. Dechelation experiments performed on phosphate buffer alone showed that phosphate may induce gadolinium release by ligand exchange when the phosphate concentration in the buffer is higher than 130 mM for an Omniscan^® concentration of 1.25 mM. This corresponds to a Gd/phosphate ratio of 10^?2. This ratio could be reached in vivo, especially in deep compartments such as bone. The presence of endogenous cations (Zn²⁺, Cu²⁺ or Ca²⁺) has also been demonstrated to accelerate the kinetics of gadolinium release, either by catalysing ligand exchange or by inducing a transmetallation mechanism. The Omniscan^® formulation was also tested and the added Ca–DTPA–BMA was shown to increase dechelation kinetics in these experiments. This striking result may question the value of the Omniscan^® formulation in the context of NSF.