Ecotoxicological profile of pyridine. Working party on ecotoxicological profiles of chemicals

Evaluation of the stability of ceftazidime/avibactam in elastomeric infusion devices used for outpatient parenteral antimicrobial therapy utilizing a national stability protocol framework

Objectives

To evaluate the stability of ceftazidime/avibactam in elastomeric infusers, utilizing the UK's Yellow Cover Document (YCD) stability testing framework, in conditions representative of OPAT practice.

Methods

Ceftazidime/avibactam was reconstituted with sodium chloride 0.9% (w/v) in two elastomeric infusers at concentrations (dose) levels of 1500/375, 3000/750 and 6000 mg/1500 mg in 240 mL. The infusers were exposed to a fridge storage (2°C-8°C) for 14 days followed by 24 h in-use temperature (32°C).

Results

After 14 days of fridge storage and subsequent 24 h exposure to 32°C, mean ± SD of ceftazidime percent remaining was 75.5% ± 1.8%, 79.9% ± 1.1%, 82.4% ± 0.6%, for Easypump, and 81.7% ± 1.2%, 82.5% ± 0.5%, 85.4% ± 1.1% for Dosi-Fuser devices at the high, intermediate and low doses tested, respectively. For avibactam, mean ± SD percent remaining was 83.2% ± 1.8%, 87.4% ± 2.0%, 93.1% ± 0.9% for Easypump, and 85.1% ± 2.0%, 86.7% ± 0.1%, 92.5% ± 0.1% for Dosi-Fuser devices. The cumulative amount of pyridine generated in the devices ranged from 10.4 mg at low dose to 76.9 mg at high dose. Regression-based simulation showed that the degradation of both ceftazidime and avibactam was <10% for at least 12 h of the running phase, if stored in a fridge for not more than 72 h prior to in-use temperature exposure.

Conclusions

Whilst not meeting the strict UK YCD criteria for ≤5% degradation, ceftazidime/avibactam may be acceptable to administer as a continuous 12 hourly infusion in those territories where degradation of ≤10% is deemed acceptable.

Mechanistic insights into pyridine exposure induced toxicity in model Eisenia fetida species: Evidence from whole-animal, cellular, and molecular-based perspectives

Pyridine and its derivatives are widely used in many applications and inevitably cause extreme scenarios of serious soil contamination, which pose a threat to soil organisms. Still, the eco-toxicological effects and underlying mechanisms of pyridine-caused toxicity toward soil fauna have not been well established. Thus, earthworms (Eisenia fetida), coelomocytes, and oxidative stress-related proteins were selected as targeted receptors to probe the ecotoxicity mechanism of extreme pyridine soil exposure targeted to earthworms by using a combination of in vivo animal experiments, cell-based in vitro tests, in vitro functional and conformational analyses, and in silico analyses. The results showed that pyridine caused severe toxicity to E. fetida at extreme environmental concentrations. Exposure of pyridine induced excessive ROS formation in earthworms, causing oxidative stress and various deleterious effects, including lipid damage, DNA injury, histopathological change, and decreased defense capacity. Also, pyridine destroyed the cell membrane of earthworm coelomic cells and triggered a significant cytotoxicity. Importantly, the intracellular ROS (e.g., O₂^-, H₂O₂, and OH·^-) was release-activated, which eventually inducing oxidative stress effects (lipid peroxidation, inhibited defense capacity, and genotoxicity) through the ROS-mediated mitochondrial pathway. Moreover, the antioxidant defence mechanisms in coelomocytes responded quickly to reduce ROS-mediated oxidative injury. It was conformed that the abnormal expression of targeted genes associated with oxidative stress in coelomic cells was activated after pyridine exposure. Particularly, we found that the normal conformation (particle sizes, intrinsic fluorescence, and polypeptide backbone structure) of CAT/SOD was destroyed by the direct binding of pyridine. Furthermore, pyridine bound easily to the active center of CAT, but preferentially to the junction cavity of two subunits of SOD, which is considered to be a reason for impaired protein function in cells and in vitro. Based on these evidences, the ecotoxicity mechanisms of pyridine toward soil fauna are elucidated based on multi-level evaluation.

High Pyridine Generation in Ceftazidime-Icodextrin Admixtures Used to Treat Peritoneal Dialysis-associated Peritonitis

PURPOSE

To investigate the amount of pyridine generated from degradation of ceftazidime in icodextrin peritoneal dialysis (PD) solutions.

METHODS

PD solutions that contained 1 and 1.5 g of ceftazidime were stored at 25 °C for 12 hours and then at 37 °C for 14 hours. An aliquot was withdrawn at predefined time points and analyzed for the concentrations of ceftazidime and pyridine.

FINDINGS

The amount of pyridine generated was >225% and 400% of its maximum recommended daily exposure in the 1- and 1.5-g ceftazidime-PD admixtures, respectively.

IMPLICATIONS

Until these results are confirmed with appropriate in vivo studies, intermittent intraperitoneal dosing of ceftazidime admixed with icodextrin should be used with caution and appropriate clinical monitoring or a suitable alternative antibiotic should be used.

Ceftazidime stability and pyridine toxicity during continuous i.v. infusion

Purpose

This article reviews the literature concerning ceftazidime stability and potential for toxicity from pyridine (a degradation product) in the light of decades of apparent safe use of this antibiotic when given by continuous i.v. infusion but recent changes in regulatory body/manufacturer advise a need to change infusion devices more frequently.

Summary

In the outpatient setting, ceftazidime is ideally administered by continuous i.v. infusion because of its short half-life and lack of post-antibiotic effect. While continuous i.v. infusion provides the optimal pharmacokinetic/pharmacodynamic profile, the frequency with which infusion devices need to be changed is critical to the practicality in the outpatient setting, especially where trained staff are required to visit the patient in their home to change the device. The rate of ceftazidime degradation (and pyridine formation) is temperature, concentration, and solvent dependent. By using the lowest effective dose (guided by pathogen minimum inhibitory concentration [MIC] so as to achieve a blood concentration ≥ 4 × MIC over the whole dosage interval), keeping ceftazidime concentration ≤ 3%, using 0.9% sodium chloride injection as diluent and maintaining temperature between 15-25°C when connected to the patient, the amount of pyridine formed over a 24-hour period can be minimized and toxicity prevented. When pathogen MIC dictates that > 6 g ceftazidime/day is required, alternative antibiotics should be considered and/or greater attention paid to temperature and concentration of the infusion solution.

Conclusion

Ceftazidime can be used safely and effectively via continuous i.v. infusion in the outpatient setting with once-daily changes of infusion device provided the concentration and temperature of the infusion solution is controlled. In this way, more frequent changes of infusion device (that increase the risk of blood-borne infection and reduce the practicality of continuous i.v. infusion in the home) can be avoided.

Mutagenic assessment of three synthetic pyridine-diaryl ketone derivatives

Nowadays, there are increasing numbers of studies about synthetic chemicals according to the supply demands of bioactive chemicals. The current study aims to investigate genotoxic potential of bioactive synthetic pyridine compounds, phenyl-3-pyridinylmethanone (1), p-tolyl-3-pyridinylmethanone (2), and 4-methoxyphenyl-3-pyridinylmethanone (3), using Ames/ Salmonella and Escherichia coli WP2 bacterial reversion mutagenicity test systems. The mutant bacterial tester strains sodium azide-sensitive Salmonella typhimurium TA1535, 9-aminoacridine-sensitive S. typhimurium TA1537, and N-methyl- N′ -nitro- N-nitrosoguanidine-sensitive E. coli WP2 uvrA were used to detect the mutagenic potential of the test compounds. The results indicated that none of the test substances showed significant mutagenic activity on S. typhimurium TA1535, TA1537, and E. coli WP2 uvrA bacterial strains up to 1 µg/plate concentrations.

Pyridine sorption from aqueous solution by rice husk ash (RHA) and granular activated carbon (GAC): parametric, kinetic, equilibrium and thermodynamic aspects

The present study deals with the adsorption of pyridine (Py) from synthetic aqueous solutions by rice husk ash (RHA) and commercial grade granular activated carbon (GAC) and reports on the kinetic, equilibrium and thermodynamic aspects of Py sorption. Batch sorption studies were carried out to evaluate the effect of various parameters, such as adsorbent dose (m), initial pH (pH0), contact time (t), initial concentration (C0) and temperature (T) on the removal of Py. The maximum removal of Py is found to be approximately 96% and approximately 97% at lower concentrations (<50 mg dm(-3)) and approximately 79.5% and approximately 84% at higher concentrations (600 mg dm(-3)) using 50 kg m(-3) and 30 kg m(-3) of RHA and GAC dosage, respectively, at 30+/-1 degrees C. Adsorption of Py is found to be endothermic in nature and the equilibrium data can be adequately represented by Toth and Redlich-Peterson isotherm equations. Py can be recovered from the spent adsorbents by using acidic water and 0.1 N H2SO4. The overall adsorption of Py on RHA and GAC is found to be in the order of GAC>RHA. Comparative assessment of adsorbents used by various investigators available in literature showed the effectiveness of BFA and RHA over other adsorbents. Spent RHA can simply be filtered, dried and used in the boiler furnaces/incinerators. Thus, its heating value can be recovered.

Effects of pyridine exposure upon structural lipid metabolism in Swiss Webster mice

Pyridine is a prototypical inducer of cytochrome P450 (CYP) 2E1, an enzyme associated with cellular oxidative stress and membrane damage. To better understand the effect of this treatment on cellular lipids, the influence of pyridine exposure (100 mg/kg/day i.p. for 5 days) on fatty acids, fatty esters, and fatty alcohol ethers in brain, heart, liver, and adipose tissue from male Swiss Webster mice was investigated. Lipid levels in cholesterol esters, triglycerides, free fatty acids, cardiolipin, sphingomyelin, and glycerylphospholipids were quantified. Pyridine altered the level and composition of lipids involved in membrane structure (i.e., sphingomyelin, phosphatidylethanolamines, and plasmalogens), energy metabolism (i.e., free fatty acids), and long-chain fatty acid transport (i.e., cholesterol esters) in a tissue-specific manner. Subtle changes in cholesterol esters were observed in all tissues. Sphingomyelin in the brain and heart were depleted in monounsaturated fatty acids (1.4- and 1.5-fold, respectively), while the liver sphingomyelin concentrations increased (1.5-fold). Pyridine exposure also increased heart free fatty acids by 1.3-fold, enriched cardiac phosphatidylethanolamine in long-chain polyunsaturated fatty acids by 1.3-fold, and depleted cardiolipin-associated plasmalogens by 3.8-fold. Phosphatidylethanolamines in the brain were also enriched in both saturated fatty acids (1.2-fold) and polyunsaturated fatty acids (1.3-fold) but were depleted in plasmalogens (2.9-fold). In particular, the levels of phosphatidylethanolamine-associated arachidonic (AA) and docosahexaenoic acid (DHA) in both brain and cardiac tissues significantly decreased following pyridine exposure. Considering the hypothetical role of plasmalogens as membrane-bound reactive oxygen scavengers, the current findings suggest that the brain and heart should be the focus of future studies on the toxicity of pyridine, as well as other CYP 2E1 inducers.

Toxicity and anaerobic biodegradability of pyridine and its derivatives under sulfidogenic conditions

Attempts were made to correlate the chemical structure of pyridine and 15 pyridine derivatives with both their biodegradability by estuarine sediment microorganisms under anaerobic conditions and also with their toxicity to the marine bacterium Vibrio fischeri Beijerinck 1889 by using the Microtox bacterial assay. Among monosubstituted pyridines, comparisons of different substituents at positions C-2, C-3, or C-4 atom of the pyridine ring showed that isomers of carboxylpyridine (COOHPYR), hydroxypyridine (OHPYR), and cyanopyridine (CNPYR) were more susceptible to biotransformation than isomers of chloropyridine (ClPYR) and methylpyridine (CH3PYR) in anoxic estuarine sediment slurries under sulfidogenic conditions. Isomers with the functional group at the C-2 or C-3 atom of the pyridine ring were biotransformed faster than those with the same functional group at C-4. The only exception was 4-ClPYR, which was biotransformed within 130 days, while 2- and 3-ClPYR continued to persist in the anoxic sediment slurries. Median effect concentrations (EC50) of pyridine and pyridine derivatives were in the range of 0.027 to 49.1 mmol/L. Pyridine derivatives with -CN and -OH functional groups tended to be less toxic, while pyridine derivatives with -CH3, -Cl, and -COOH functional groups tended to be more toxic. Isomers with the substituent at C-2 were less toxic than the C-3 or C-4 isomers. There was no clear correlation between the pseudo-first-order rate constants for the microbial transformation of pyridine and its derivatives and their toxicity to the marine bacterium.

Comparison of the effects of pyridine and its metabolites on rat liver and kidney

In order to evaluate the possibility that the metabolism of pyridine may be important for its toxic actions, pyridine was compared with pyridine N-oxide, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine and pyridinium methyliodide in rats given equal molar doses of the chemicals i.p. Hepatoxicity was assessed by measuring serum sorbitol dehydrogenase, nephrotoxicity by determining increases in blood urea nitrogen and serum creatinine, and influence on xenobiotic metabolism by measuring changes in p-nitrophenol hydroxylase and ethoxyresorufin and benzyloxyresorufin dealkylase activities. After a single dose of 2.5 mmol/kg, pyridinium methyliodide was the only compound that was lethal whereas 2-hydroxypyridine was the only one that caused significant hepatoxicity. Pyridine, pyridine N-oxide, 3-hydroxypyridine and 4-hydroxypyridine were effective inducers of xenobiotic metabolism. Thus the metabolites of pyridine may play a role, either singly or collectively, in the actions of pyridine.

Oxidative metabolism of 14C-pyridine by human and rat tissue subcellular fractions

1. The oxidative metabolism of 14C-pyridine by human and rat microsomal fractions has been studied. Metabolites were separated by h.p.l.c. employing continuous radioactivity monitoring of the column effluent. 2. Human liver microsomal fractions incubated with an NADPH-generating system and oxygen formed pyridine N-oxide (PNO) at an average rate of 275 pmol/min per mg protein, 2-pyridone (2PO) at 207 pmol/min per mg and 4-pyridone (4PO) at 154 pmol/min per mg. One human subject formed 3-hydroxypyridine N-oxide in addition to the other metabolites. 3. Human kidney microsomal fractions formed PNO, 2PO and 4PO at rates similar to those with human liver microsomal fractions, whereas human lung microsomal fractions formed the metabolites at less than half the rate. 4. Metabolism of pyridine by human liver microsomal fractions was inhibited 54% by nitrogen, 34% by 80% carbon monoxide-20% oxygen, and 20% by metyrapone. 2-Diethylaminoethyl-2,2-diphenylvalerate HCl (SKF-525A) did not inhibit pyridine metabolism. 5. Liver microsomal fractions from non-induced rats metabolized pyridine to PNO at a rate of 19 pmol/min per mg protein, 2PO at 17 pmol/min per mg and 4PO at 61 pmol/min per mg. 6. There was no pyridine metabolism by human or rat tissue cytosolic fractions incubated under the same conditions.

Degradation of Pyridine by Micrococcus luteus Isolated from Soil

An organism capable of growth on pyridine was isolated from soil by enrichment culture techniques and identified as Micrococcus luteus. The organism oxidized pyridine for energy and released N contained in the pyridine ring as ammonium. The organism could not grow on mono- or disubstituted pyridinecarboxylic acids or hydroxy-, chloro-, amino-, or methylpyridines. Cell extracts of M. luteus could not degrade pyridine, 2-, 3-, or 4-hydroxypyridines or 2,3-dihydroxypyridine, regardless of added cofactors or cell particulate fraction. The organism had a NAD-linked succinate-semialdehyde dehydrogenase which was induced by pyridine. Cell extracts of M. luteus had constitutive amidase activity, and washed cells degraded formate and formamide without a lag. These data are consistent with a previously reported pathway for pyridine metabolism by species of Bacillus, Brevibacterium , and Corynebacterium. Cells of M. luteus were permeable to pyridinecarboxylic acids, monohydroxypyridines, 2,3-dihydroxypyridine, and monoamino- and methylpyridines. The results provide new evidence that the metabolism of pyridine by microorganisms does not require initial hydroxylation of the ring and that permeability barriers do not account for the extremely limited range of substrate isomers used by pyridine degraders.