Presence of other rare earth metals in gadolinium-based contrast agents.

Gadolinium-based contrast agents (GBCA) are widely used to enhance tissue contrast during magnetic resonance imaging (MRI) procedures. However, free Gadolinium (Gd) is undesirable as a drug substance, due to its high toxicity. Consequently, a coordinating ligand is required to keep it in solution and to increase tolerance. In order to achieve an adequate performance, GBCA must be administered in relatively large amounts. Chelate amounts are around 13-20 g and for Gd alone, this may amount to 3.3 g. Taking into account the route of administration, impurities in GBCA may be significant. Gadolinium occurs in nature along with 16 other elements known collectively as rare earth metals (RE), which are found throughout the earth's crust in minerals such as monazite. Gadolinium oxide corresponds to 0.7-4.0% of the RE present in minerals, and the sum concentration of RE in minerals is around 4%. Rare earth metals are difficult to separate, as the chemical and physical properties of one RE are significantly similar to those of others. In this study, the presence of other RE in GBCA formulations was investigated. Different lots of Magnevist®, Viewgam®, OptiMARK®, Omniscan®, Dotarem®, and Gadovist® were analyzed. Inductively-coupled plasma mass spectrometry and atomic absorption spectrometry were used for RE determination. Procedure optimization included sample decomposition and method validation for element determination. The results showed that Sc, Y, La, Ce, Pr, Nd, Eu, Tb, Tm, Dy, Ho, and Er were present in the 22 samples analyzed. Terbium, Thulium, Europium, and Lanthanum were, on average, found in the highest amounts, which were 0.42 mg/L, 0.17 mg/L, 0.17 mg/L, and 0.16 mg/L, respectively. These results could be attributed to the similarity among Europium, Gadolinium, and Terbium. They are in sequence in the periodic table and therefore present very close ionic radii, restricting their separation. Considering the sum of all RE, Viewgam® was the most contaminated formulation (mean of 2.16 mg/L) and Magnevist® the least (mean of 0.64 mg/L). Although the RE are chemically similar, the other RE do not perform as Gd as a contrast agent; therefore, their presence in formulations may be a matter of concern.

Extraction/Leaching of Metal-Containing Additives from Polyvinyl Chloride, Ethyl Vinyl Acetate, and Polypropylene Bags and Infusion Sets into Infusion Solutions.

Flexible medical devices are primarily made of plasticized polyvinyl chloride (PVC). In recent times, to avoid undesired migration of the PVC plasticizers, ethyl vinyl acetate (EVA) and polypropylene (PP) has replaced PVC. Nevertheless, other additives are necessary to generate useful polymeric materials. Metallic species present in such additives can also leach out into the infusion solutions. The migration of barium (Ba), cadmium (Cd), lead (Pb), tin (Sn), and zinc (Zn) from devices made from PVC, EVA, and PP was evaluated. Bags and infusion sets were decomposed and their metallic contents analyzed. Glucose, NaCl, and Tween 80 were assessed as extraction media. These solutions were stored in PVC, EVA, and PP bags, heat-sterilized, and stored for 8 months at room temperature. Aliquots were taken before and after sterilization and then once per month to determine the contents of the metals. Commercial glucose and NaCl infusions were analyzed by taking aliquots of the solutions from the bags and from the administration set after their administration to patients. The three polymers contained the five metals. Ba was found in the highest concentration in all samples, with a mean of 8.0 mg/kg in PVC, 4.2 mg/kg in EVA, and 4.7 mg/kg in PP samples. Despite this, the only element that migrated into the glucose, NaCl, and Tween 80 solutions was Zn. The same result was found for the commercial glucose and NaCl infusions. Moreover, the Zn concentration in the administration sets was on average 52% higher than that found in the bags.LAY ABSTRACT: Flexible medical devices for infusions and artificial nutrition are made of plastics, such as polyvinyl chloride (PVC), ethyl vinyl acetate (EVA), and polypropylene (PP). These polymers contain additives necessary to generate useful materials. Metallic species present in these additives can leach out into the infusion solutions and come into contact with patients. To assess the risk of patient exposure to these metals, we evaluated the migration behavior of barium (Ba), cadmium (Cd), lead (Pb), tin (Sn), and zinc (Zn) from devices made from PVC, EVA, and PP. Bags and infusion sets were analyzed. Glucose, NaCl, and Tween 80 were investigated as extraction media. The three polymers contained the five metals. Ba was found in the highest concentration in all samples. Despite this, the only element that migrated into the glucose, NaCl, and Tween 80 solutions was Zn.

Determination of Antimony in Pharmaceutical Formulations and Beverages Using High-Resolution Continuum-Source Graphite Furnace Atomic Absorption Spectrometry.

A sensitive and accurate method, employing high-resolution continuum source atomic absorption spectrometry, for the determination of antimony (Sb) was developed. Conditions such as pyrolysis and atomization temperatures, the use of chemical modifiers, and sample pretreatment were optimized for the determination of Sb in pharmaceutical preparations and beverages stored in polyethylene terephthalate (PET) containers. In addition to container analysis, the influence of time of contact, temperature, and content composition on the migration of Sb was investigated. Twenty-six samples were periodically analyzed until finalize 1 year bottling. Eight mineral water samples were analyzed after storage at temperatures from 40 to 80°C for 48 h. Five different-colored PET samples were stored at 80°C for 20 days and periodically analyzed. Bottles, containing from 46.4 mg/kg Sb (amber PET) to 91.6 mg/kg Sb (colorless PET), leached Sb depending on the content ingredients, time of contact, and temperature. Although drinking water itself did not promote Sb migration at room temperature, juices and medicines did. After 1 year of storage, the Sb level in the samples ranged from 5 to 50 µg/L. The rate of leaching depended on the temperature, which was slow below 60°C, but rapidly increased at 60-80°C. The higher the Sb content in the bottle, the higher the amount of migration. Because Sb is a possible carcinogen to humans, containers for pharmaceutical use should be better controlled, and factors that increase Sb leaching in products that are widely consumed should be avoided.

Silicon Reverses Lipid Peroxidation but not Acetylcholinesterase Activity Induced by Long-Term Exposure to Low Aluminum Levels in Rat Brain Regions.

Aluminum (Al) is the most widely distributed metal in the environment and is extensively used in daily life leading to easy exposure to human beings. Besides not having a recognized physiological role, Al may produce adverse effects through the interaction with the cholinergic system contributing to oxidative stress. The present study evaluated, in similar conditions of parenteral nutrition, whether the reaction of silicon (SiO2) with Al(3+) to form hydroxyaluminosilicates (HAS) reduces its bioavailability and toxicity through intraperitoneal administrations of 0.5 mg Al/kg/day and/or 2 mg Si/kg/day in Wistar rats. Al and Si concentrations were determined in rat brain tissue and serum. Acetylcholinesterase (AChE) activity and lipid peroxidation (LPO) were analyzed in the cerebellum, cortex, hippocampus, striatum, hypothalamus, and blood. An increase in the Al concentration was verified in the Al + Si group in the brain. All the groups demonstrated enhanced Si compared to the control animals. Al(3+) increased LPO measured by thiobarbituric acid reactive substances (TBARS) in cerebellum and hippocampus, whereas SiO2 reduced it when compared with the control group. An increase of AChE activity was observed in the Al-treated group in the cerebellum whereas a decrease of this enzyme activity was observed in the cortex and hippocampus in the Al and Al + Si groups. Al and Si concentrations increased in rat serum; however, no effect was observed in blood TBARS levels and AChE activity. SiO2 showed a protective effect in the hippocampus and cerebellum against cellular damage caused by Al(3+)-induced lipid peroxidation. Thus, SiO2 may be considered an important protector in LPO induced by Al(3+).

Accumulation, elimination, and effects of parenteral exposure to aluminum in newborn and adult rats.

Aluminum (Al) delivered to preterm infants via parenteral nutrition may exceed the limit of 5 µg/kg/day set by the US Food and Drug Administration. This study evaluated the effect of the administration of an equivalent amount of Al (0.12 mg/kg/day) to newborn rats. The study included the administration of a higher amount of Al (24.8 mg/kg/day) not only to newborn rats but also to adult (2- and 4-month-old) rats. Aluminum was intraperitoneally administered for a period of 10 days. Newborn animals were evaluated for developmental changes every day starting from the second day after birth. Twenty days after the last administration, 10 animals were killed and their organs were removed; the remainders were killed on day 40. A dosage of 24.8 mg/kg/day was administered to the two groups of adult rats, which were killed following the same protocol after 20 and 40 days. The results of physical parameters and developmental and behavioral tests were not conclusive and no significant differences were observed between the lower and higher Al dose and control groups. The group that received 0.12 mg/kg/day showed significant differences in Al accumulation only in the liver and muscle. The groups that received a higher dose of Al showed an accumulation in all tissues among all age groups studied, but the newborn group showed the greatest accumulation (results for day 20). After 40 days, Al content in all tissues decreased more than 50% in this group, whereas among the adults, the Al content increased or remained constant. An increase in age correlated with a lower elimination rate. Considering the ongoing human Al exposure, along with its age-related elimination rate, Al accumulation in the body may be long-lasting.

Aluminum in erythropoietin formulations: lyophilized versus liquid forms.

BACKGROUND: Erythropoietin (EPO) formulations may comprise aluminum (Al) as a contaminant. Due to the toxicity of Al in chronic kidney disease patients, possible sources of Al were investigated. Since EPO formulations are stored in container-closure systems made of glass and rubber, and both contain Al, formulation ingredients may enable its leaching into the solution during shelf-life. METHODS: Individual solutions of formulation ingredients were stored in new glass vials and in contact with the rubber stopper and kept at 4 ± 2 °C. For 12 months, aliquots of each solution were collected for analysis. Fifteen commercial samples of EPO were analyzed for their Al content. Aluminum was determined by atomic absorption spectrometry. RESULTS: Glass and rubber are sources of Al for EPO formulations. Storage assay showed that citrate and phosphate (used as buffers) extracted high amounts of Al from the container/closure parts. The most important difference, however, was found when comparing liquid and lyophilized samples. While in liquid forms the Al level reached 943 µg/L, in lyophilized forms the level did not exceed 20 µg/L. The container system was also confirmed as a source of Al in reconstituted lyophilized samples. Al in reconstituted samples stored in their own vials increased 19-fold in 12 months. Lyophilized powders stored for 2 years in glass vials contained less Al than in 1 month after dissolution. CONCLUSION: The difference in the Al measured in liquid forms of EPO and in lyophilized powders suggests that the latter would be the best pharmaceutical form for CKD patients.

Evidence for aluminum-binding erythropoietin by size-exclusion chromatography coupled to electrothermal absorption atomic spectrometry.

Erythropoietin (EPO) is a glycoprotein that stimulates erythropoiesis and is clinically used for treating anemia during chronic renal failure and for anemia in preterm infants. EPO formulations usually have elevated rates of contamination due to aluminum (Al), which is toxic to both types of patients. Size-exclusion chromatography (SEC) coupled with graphite furnace atomic absorption spectrometry (GF AAS) was employed to separate proteins and to quantify the amount of aluminum present in the elution volume corresponding to EPO and, therefore, to evaluate possible binding. Because EPO formulations contain human serum albumin (HSA), a chromatographic method was optimized for the separation of these proteins. Subsequent to the chromatographic separation, 1-mL fractions of the column effluent were collected, and the Al content in these aliquots was measured by GF AAS. EPO and HSA samples were incubated with Al for 4h at 4°C and 37°C as well as for 16 h at 4°C and 37°C. Afterwards, they were injected into the chromatographic system. These samples were also submitted to ultrafiltration (10 and 50 kDa membranes), and Al was measured in the ultrafiltrates. The results showed that Al was present in the eluent volume corresponding to the EPO peak but not in the HSA peak in the chromatograms. Temperature strengthened the interaction because the Al present in the EPO fraction was 3 times higher at 37°C compared to 4°C. Thirty-eight percent of the Al present in a 2.4 µg/mL EPO standard solution, and approximately 50% of the Al in formulation samples containing approximately 11 µg/mL EPO and either citrate or phosphate, were non-ultrafiltrable, which suggests that EPO is an effective Al acceptor in vitro.

Cyclooxygenase-2/PGE2 pathway facilitates pentylenetetrazol-induced seizures.

Cyclooxygenases (COXs) are rate-limiting enzymes in the metabolic pathways in which arachidonic acid is converted to prostaglandins. COX-2 is the isoform induced at injury/inflammation sites and expressed constitutively in a few tissues, such as the central nervous system, and plays a role in neurodegenerative diseases associated with increased excitatory activity. However, the role of COX-2 and its main product, prostaglandin E(2) (PGE(2)), in the convulsive states is not fully established. In this study we showed that the selective COX-2 inhibitor, celecoxib (at the dose of 2mg/kg, but not at the doses of 0.2 or 20mg/kg, p.o.), protects against the seizures induced by pentylenetetrazol (PTZ, 60 mg/kg, i.p.). The role of PGE(2) in the convulsions induced by PTZ was further investigated by administering anti-PGE(2) antibodies (4 microg/2 microl, i.c.v.), and assessing electroencephalographic changes induced by PTZ (PTZ, 60 mg/kg, i.p.). Anti-PGE(2) antibodies attenuated PTZ-induced seizures in rats. In addition, combining PGE(2) (100 ng/2 microl, i.c.v.) with a subconvulsant dose of PTZ (20mg/kg, i.p.) caused seizures, further supporting a role for this prostaglandin in the convulsions induced by PTZ. Finally, we showed that the anticonvulsant action of celecoxib (2mg/kg, p.o.) was reversed by the intracerebroventricular administration of PGE(2) (10 ng/2 microl, i.c.v.). These data constitute strong converging pharmacological evidence supporting a facilitatory role for the COX-2/PGE(2) pathway in the seizures induced by PTZ. However, whether selective COX-2 inhibitors are safer anti-inflammatory drugs for epileptic patients than nonspecific inhibitors remains to be determined.