Monitoring of the degradation kinetics of diatrizoate sodium to its cytotoxic degradant using a stability-indicating high-performance liquid chromatographic method.

The X-ray diagnostic agent sodium diatrizoate (DTA) was studied for chemical degradation. The 3,5-diamino derivative was found to be the alkaline and acidic degradation product. The 3,5-diamino degradate is also the synthetic precursor of DTA and it is proved to have cytotoxic and mutagenic effects. A sensitive, selective and precise high-performance liquid chromatographic stability-indicating method for the determination of DTA in the presence of its acidic degradation product and in pharmaceutical formulation was developed and validated. Owing to the high toxicity of the degradation product, the kinetics of the acidic degradation process was monitored by the developed RP-HPLC method. The reaction was found to follow pseudo-first order kinetics. The kinetic parameters such as rate constant (K) and half-life (t½ ) were calculated under different temperatures and acid concentrations; activation energy was estimated from the Arrhenius plot. The developed RP-HPLC method depends on isocratic elution of a mobile phase composed of methanol-water (25:75 v/v; pH adjusted with phosphoric acid), and UV detection at 238 nm. The method showed good linearity over a concentration range of 2-100 µg/mL with mean percentage recovery of 100.04 ± 1.07. The selectivity of the proposed method was tested using laboratory-prepared mixtures. The proposed method has been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives and the results were statistically compared with the official USP method. Validation of the proposed method was performed according to International Conference on Harmonization guidelines.

Effect of oxidation and catalytic reduction of trace organic contaminants on their activated carbon adsorption.

The combination of ozonation and activated carbon (AC) adsorption is an established technology for removal of trace organic contaminants (TrOCs). In contrast to oxidation, reduction of TrOCs has recently gained attention as well, however less attention has gone to the combination of reduction with AC adsorption. In addition, no literature has compared the removal behavior of reduction vs. ozonation by-products by AC. In this study, the effect of pre-ozonation vs pre-catalytic reduction on the AC adsorption efficiency of five TrOCs and their by-products was compared. All compounds were susceptible to oxidation and reduction, however the catalytic reductive treatment proved to be a slower reaction than ozonation. New oxidation products were identified for dinoseb and new reduction products were identified for carbamazepine, bromoxynil and dinoseb. In terms of compatibility with AC adsorption, the influence of the oxidative and reductive pretreatments proved to be compound dependent. Oxidation products of bromoxynil and diatrizoic acid adsorbed better than their parent TrOCs, but oxidation products of atrazine, carbamazepine and dinoseb showed a decreased adsorption. The reductive pre-treatment showed an enhanced AC adsorption for dinoseb and a major enhancement for diatrizoic acid. For atrazine and bromoxynil, no clear influence on adsorption was noted, while for carbamazepine, the reductive pretreatment resulted in a decreased AC affinity. It may thus be concluded that when targeting mixtures of TrOCs, a trade-off will undoubtedly have to be made towards overall reactivity and removal of the different constituents, since no single treatment proves to be superior to the other.

Degradation of the long-resistant pharmaceutical compounds carbamazepine and diatrizoate using mixed microbial culture.

The microbial degradation of two recalcitrant pharmaceutical compounds, carbamazepine (CBZ) and diatrizoate (DTZ), was studied in laboratory batch experiments. We used a defined mixed microbial culture comprising four distinct microbial species that were previously known to have high decomposition capacity toward recalcitrant substances. Biological decomposition in liquid phase cultures for either CBZ or DTZ, or in a combination of the two, was conducted for 12 days. DTZ and CBZ were degraded by 43.2% and 60%, respectively from an initial concentration of 100 µg L(-1). When degradation was assessed using a mixture of the two compounds, the initial degradation rates of CBZ and DTZ were lower than those observed in the single-compound study. However, the final cumulative removal efficiency was very similar. The extent of dissolved organic carbon (DOC) removal was correlated with the degradation of the pharmaceuticals.

Biogenic palladium enhances diatrizoate removal from hospital wastewater in a microbial electrolysis cell.

To decrease the load of pharmaceuticals to the environment, decentralized wastewater treatment has been proposed for important point-sources such as hospitals. In this study, a microbial electrolysis cell (MEC) was used for the dehalogenation of the iodinated X-ray contrast medium diatrizoate. The presence of biogenic palladium nanoparticles (bio-Pd) in the cathode significantly enhanced diatrizoate removal by direct electrochemical reduction and by reductive catalysis using the H(2) gas produced at the cathode of the MEC. Complete deiodination of 3.3 µM (2 mg L(-1)) diatrizoate from a synthetic medium was achieved after 24 h of recirculation at an applied voltage of -0.4 V. An equimolar amount of the deiodinated metabolite 3,5-diacetamidobenzoate (DAB) was detected. Higher cell voltages increased the dehalogenation rates, resulting in a complete removal after 2 h at -0.8 V. At this cell voltage, the MEC was also able to remove 85% of diatrizoate from hospital effluent containing 0.5 µM (292 µg L(-1)), after 24 h of recirculation. Complete removal was obtained when the effluent was continuously fed at a volumetric loading rate of 204 mg diatrizoate m(-3) total cathodic compartment (TCC) day(-1) to the MEC with a hydraulic retention time of 8 h. At -0.8 V, the MEC system could also eliminate 54% of diatrizoate from spiked urine during a 24 h recirculation experiment. The final product DAB was demonstrated to be removable by nitrifying biomass, which suggests that the combination of a MEC and bio-Pd in its cathode offers potential to dehalogenate pharmaceuticals, and to significantly lower the environmental burden of hospital waste streams.

Palladium nanoparticles produced by fermentatively cultivated bacteria as catalyst for diatrizoate removal with biogenic hydrogen.

A new biological inspired method to produce nanopalladium is the precipitation of Pd on a bacterium, i.e., bio-Pd. This bio-Pd can be applied as catalyst in dehalogenation reactions. However, large amounts of hydrogen are required as electron donor in these reactions resulting in considerable costs. This study demonstrates how bacteria, cultivated under fermentative conditions, can be used to reductively precipitate bio-Pd catalysts and generate the electron donor hydrogen. In this way, one could avoid the costs coupled to hydrogen supply. The catalytic activities of Pd(0) nanoparticles produced by different strains of bacteria (bio-Pd) cultivated under fermentative conditions were compared in terms of their ability to dehalogenate the recalcitrant aqueous pollutants diatrizoate and trichloroethylene. While all of the fermentative bio-Pd preparations followed first order kinetics in the dehalogenation of diatrizoate, the catalytic activity differed systematically according to hydrogen production and starting Pd(II) concentration in solution. Batch reactors with nanoparticles formed by Citrobacter braakii showed the highest diatrizoate dehalogenation activity with first order constants of 0.45 ± 0.02 h⁻¹ and 5.58 ± 0.6 h⁻¹ in batches with initial concentrations of 10 and 50 mg L⁻¹ Pd, respectively. Nanoparticles on C. braakii, used in a membrane bioreactor treating influent containing 20 mg L⁻¹ diatrizoate, were capable of dehalogenating 22 mg diatrizoate mg⁻¹ Pd over a period of 19 days before bio-Pd catalytic activity was exhausted. This study demonstrates the possibility to use the combination of Pd(II), a carbon source and bacteria under fermentative conditions for the abatement of environmental halogenated contaminants.

Absorption of L-lysine diatrizoate from the gastrointestinal tract: the effect of surgery, inflammation, and neoplasia.

BACKGROUND AND AIMS: To ascertain whether the absorption of L-lysine diatrizoate, a sodium-free salt of the contrast-giving diatrizoic acid from the gastrointestinal tract is increased by surgery, inflammation, and neoplasia. PATIENTS AND METHODS: The prospective study comprised 32 patients who were undergoing radiological examination of the upper gastrointestinal tract with a contrast medium containing L-lysine diatrizoate and 52 further patients who were undergoing examination of the lower gastrointestinal tract in the same way. The concentration of diatrizoic acid was determined by high-pressure liquid chromatography in blood samples taken before and immediately after the radiological examinations. The results were examined in terms of sex, age, surgical history, and any evidence of inflammatory or neoplastic diseases. RESULTS: The serum diatrizoic acid concentration in patients tested after oral administration was 3.62 microg/ml. In patients who had undergone operation the titer was lower than in those who had not been operated on. Serum diatrizoic acid concentration in patients tested after rectal administration was 0.30 microg/ml. In patients suffering from inflammatory conditions or neoplasms the titer was significantly higher than in the other patients. CONCLUSION: The L-lysine salt of diatrizoic acid is absorbed in larger amounts from the upper gastrointestinal tract than from the lower. Absorption is not increased after surgical operations on the viscera. However, inflammatory conditions and neoplasms involving the large bowel increase the uptake of the contrast medium from the intestine.

[Absorption of L-lysine diatrizoate from the gastrointestinal tract: the influence of surgery, inflammation and neoplasia]. / Resorption von L-Lysin-Diatrizoat aus dem Gastrointestinaltrakt unter dem Einfluss von Operation, Entzündung und Neoplasie.

PURPOSE: To ascertain whether the absorption of L-lysine diatrizoate, a sodium-free salt of the contrast-giving diatrizoic acid, from the gastrointestinal tract is increased by surgery, inflammation or neoplasia. MATERIAL AND METHODS: Using contrast medium containing L-lysine diatrizoate for intestinal opacification, this prospective study compared 32 radiographic examinations of the upper gastrointestinal tract with 52 radiographic examination of the lower gastrointestinal tract. In blood samples taken from the patients immediately after the radiographic examinations, the concentration of diatrizoic acid was determined by high pressure liquid chromatography. The results were correlated with sex, age, surgical history and any evidence of inflammatory or neoplastic diseases. RESULTS: The serum diatrizoic acid concentration in patients after oral administration was 3.62 (95% CI, 2.86 - 10.17) microg/ml. The titer was lower in patients who had undergone abdominal surgery than in patients without surgery. Serum diatrizoic acid concentration in patients after rectal administration was 0.30 (95% CI, 0.13 - 0.60) microg/ml. The titer was significantly higher (p < 0.05) in patients suffering from inflammatory conditions or neoplasms than in the other patients. CONCLUSION: The L-lysine salt of diatrizoic acid is absorbed in larger amounts from the upper than from the lower gastrointestinal tract. Absorption is not increased after abdominal surgery. However, inflammatory conditions and neoplasms of the large bowel increase the uptake of contrast medium from the intestine.

Biodegradation of the iodinated X-ray contrast media diatrizoate and iopromide.

The degradation of the iodinated contrast media diatrizoate and iopromide was investigated in laboratory tests. With regard to the expected behaviour of the contrast media in the environment, test systems with activated sludge, river water and river water plus sediment were established. In some of the experiments 14C-labelled contrast media were used to study degradation at low concentrations and to detect the transformation products. Degradation by as well as binding to aerobic-activated sludge of diatrizoate was poor, suggesting that this substance is hardly retained in sewage treatment plants. In systems with river water and sediment deacetylation of diatrizoate started after a lag period of 3 weeks and followed first order kinetics with rate constants of approximately 0.15 day-1. Two metabolites were formed that were stable until day 200 of aerobic incubation. Finally, further transformation of the aerobic metabolites was observed under anoxic conditions. In activated sludge, approximately 85% of iopromide were transformed into two metabolites. Like the parent compound they were highly hydrophilic and less than 16% were bound to sludge solids. In water/sediment systems, disappearance of iopromide started spontaneously with a first order constant of 0.04 day-1. One metabolite that was stable throughout the incubation period was formed with a delay of 20 days. In river water the concentration-dependent disappearance of iopromide was studied. The shortest half-life was 3.1 days at a concentration of 16.0 mumol l-1 and increased at concentrations below and above this value. The metabolites of iopromide were not identified, but partial deiodination of iopromide was shown. Mineralisation of the two contrast media or their metabolites to carbon dioxide was not observed.

Transformation of the ionic X-ray contrast agent diatrizoate and related triiodinated benzoates by Trametes versicolor.

Iodinated X-ray contrast agents are considered to be nondegradable by microorganisms. The decomposition of the ionic X-ray contrast agents Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoic acid) and Iodipamide (3,3'-adipoyl-diimino-di(2,4,6-triiodobenzoic acid) and related triiodinated benzoates (Acetrizoate [3-acetylamino-2,4, 6-triiodobenzoic acid] and Aminotrizoate [3-amino-2,4, 6-triiodobenzoic acid]) by Trametes versicolor has been investigated. The fungus was able to transform all tested triiodinated benzoates cometabolically. During transformation of these compounds, iodide was released, but deiodination was not complete. T. versicolor liberated traces of 14CO2 from uniformly ring-14C-labeled Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoate). Various extracellular metabolites were detected during transformation of the different substances. In the transformation of Diatrizoate, the three main metabolites were identified as 3,5-di(acetamido)-2, 6-diiodobenzoic acid, 3,5-di(acetamido)-2,4-diiodobenzoic acid, and 3,5-di(acetamido)-2-iodobenzoic acid, suggesting reductive deiodinations in steps as initial transformation steps.

Liquid chromatographic assay of diatrizoic acid and its diiodo degradation products in radio-opaque solutions.

A liquid chromatographic method is described for the analysis of diatrizoic acid (2,4,6-triiodo-3,5-diacetamidobenzoic acid) and its 2,4- and 2,6-diiodo degradation products in radio-opaque injection solutions. The method is accurate, precise, and linear at a concentration range of 5-50 ppm.

Pristane retards clearance of particulate materials from the peritoneal cavity of laboratory mice.

The effect of intraperitoneal pristane on the movement of India ink particles and water-based radio-opaque dye injected into the peritoneal cavity of mice was examined. There was a marked difference between pristane-treated mice and unmanipulated controls in terms of particle retention; unmanipulated mice cleared India ink particles via lymphatic drainage within 24 h following injection, whereas pristane-treated mice retained particles for as long as 22 days post-injection. In contrast, all mice displayed similar kinetics of removal of radio-opaque dye. We conclude that the movement of particulate matter from the peritoneal cavity is retarded in pristane-treated mice whereas removal of water-based materials is unaffected. The implications for generation of ascites using hybridoma cells in pristane-primed mice is discussed.

Penetration of vascular contrast media into brain tissue and cerebrospinal fluid. An experimental study in rats.

Recent studies suggest that intravenously administered contrast media (CM) penetrate into cerebrospinal fluid (CSF), and the concentration of CM in CSF increases significantly following acetazolamide or probenecid pretreatment. However, corresponding levels of CM in brain tissue and extracellular fluid (ECF) have not been reported. Adult anesthetized rats were injected intravenously with sodium/meglumine diatrizoate and iohexol. The control group received no pretreatment, and the pretreated group received acetazolamide and probenecid before the CM. The amount of each contrast agent was measured in brain tissue and in CSF by high performance liquid chromatography. Pretreated animals attained significantly higher CSF concentrations of diatrizoate and iohexol than control animals. However, tissue ECF concentrations in pretreated animals were not significantly different than in control animals for either agent. The results are consistent with the idea that a flushing action of CSF helps to remove CM from the brain ECF.

Vicarious excretion of water-soluble contrast media into the gallbladder in patients with normal serum creatinine.

Ten patients with normal serum creatinine and no evidence of acute cholecystitis were found to have vicarious excretion of water-soluble contrast media into the gallbladder 20 minutes to 72 hours after injection. Eight of the ten had unilateral renal pathology. Two patients, however, had bilaterally normal kidneys. The patients had been injected with either diatrizoate, iothalamate, or iodamide. The mechanisms and pathophysiology of vicarious contrast excretion are discussed. The vicarious excretion of intravascular contrast in the gallbladder does not in itself indicate renal or hepatobiliary disease. Although commonly associated with unilateral renal pathology, vicarious gallbladder excretion of urographic contrast may be a normal variant in some patients.

Gallbladder opacification in infants following high dose angiocardiography.

Seven infants in congestive heart failure underwent high dose angiocardiography for diagnosis of severe congenital heart disease and subsequently displayed delayed opacification of the gallbladder. Biliary excretion of sufficient volume to opacify the gallbladder occurred despite structurally normal kidneys and no evidence of renal failure. Decreased renal clearance of contrast due to generalized diminution of glomerular filtration is postulated. The high doses of contrast and slow renal clearance allowed a relatively increased rate of hepatobiliary excretion and subsequent observation of the opacified gallbladder on abdominal radiographs. This phenomenon may not be as uncommon as is generally thought but its timing and location often do not allow an opportunity to make this observation.

Characterization of liposomes containing iodine-125-labeled radiographic contrast agents.

Multilamellar liposomes were prepared containing either iodine-125-labeled (125I) diatrizoate or 125-I labeled iotrol in their aqueous phase. The in vitro permeabilities of liposomes containing both contrast agents were measured in the presence of saline and serum at 37 degrees C. Two different phospholipid compositions were studied: phosphatidylcholine/cholesterol/stearylamine (PC/C/S, 8: 1:1 molar ratio) and distearoylphosphatidylcholine/sphingomyelin (DSPC/SM, 5:2 mole ratio). In saline, similar permeabilities were observed for the four phospholipid-contrast agent combinations. In serum, however, leakage of 125I activity was 2 to 3 times greater from PC/C/S liposomes than from vesicles composed of DSPC/SM. When PC/C/S liposomes that contained 125I-diatrizoate were injected into rats, the clearance half-times for 125I activity from the liver, spleen, and whole body were 4.4 hours, 4.5 hours, and 2.8 hours, respectively. Liposomes composed of DSPC/SM cleared at a significantly slower rate from the liver, spleen, and whole body with half-times of 24.0 hours, 18.4 hours, and 17.2 hours observed from these tissues, respectively.

Comparison of diatrizoate, iopamidol, and ioxaglate for the contrast enhancement of experimental hepatic tumors in CT.

The accumulation of diatrizoate and two new low osmolality contrast agents, iopamidol and ioxaglate, was investigated in three experimental tumors (a well differentiated mammary adenocarcinoma, a poorly differentiated colon carcinoma, and a hepatoma) in the rat. All three tumors were implanted into the liver 12 to 14 days prior to intravenous injection of the contrast agents in a dose of 300 mg iodine per kg. Iodine concentrations were determined in blood, liver, and tumors at 1, 5, 10, and 30 minutes using x-ray energy spectrometry. Ratios between tumor iodine and blood iodine concentrations increased more with time with diatrizoate than either iopamidol or ioxaglate and were at 30 minutes significantly greater for diatrizoate than the other two agents. This suggests that the contrast medium efflux from the vascular compartment into the extravascular compartment of all tumors is greater for diatrizoate than either iopamidol or ioxaglate. Although it is known from clinical experience that the differential enhancement between hypodense hepatic tumors and liver parenchyma decreases rapidly with time after contrast administration, this investigation suggests that the substitution of diatrizoate by either iopamidol or ioxaglate should not affect appreciably the contrast enhancement in this condition in dynamic CT completed within the first minutes after contrast administration. In a later phase, after contrast administration, however, both iopamidol and ioxaglate should conceal hypodense hepatic tumors less than diatrizoate.

Pulmonary edema following high intravenous doses of diatrizoate in the rat. Effects of corticosteroid pretreatment.

Serious adverse reactions to intravenous contrast media are rare but of major concern. Corticosteroids are the most commonly used drugs for prophylaxis but there is little documentation of their effectiveness. Controversy also exists about the optimum regime for these drugs. A rat model was used to evaluate the effect of methylprednisolone pretreatment for contrast media-induced pulmonary edema. Rats were given 40 mg methylprednisolone/kg intravenously at various time intervals before the intravenous injection of a high dose of diatrizoate (6 g I/kg). The combination of one dose of methylprednisolone at 24 hours plus another dose at 0.5 hours was the only regimen that caused a significant reduction in the degree of pulmonary edema induced by contrast media. This result provides support for the clinical regimen utilizing iterated doses of corticosteroids over a prolonged period of time.

Clinical comparison of Hexabrix, iopamidol, and Urografin-60 in whole body computed tomography.

Urografin 60, iopamidol and Hexabrix were studied in patients undergoing body CT scans to examine the pharmacodynamics of these contrast agents. Immediately following rapid injection, the lower osmolality media, Hexabrix and iopamidol, gave greater aortic concentration of iodine in addition to higher concentrations in the liver and spleen. These two agents also provided significantly better renal enhancement than Urografin 60, with Hexabrix giving higher levels than iopamidol. The higher early vascular concentrations of Hexabrix and iopamidol and the relative absence of side effects due to hyperosmolality and decreased toxicity may have advantages in dynamic CT scanning.

[Contrast medium elimination by hemodialysis]. / Kontrastmittel-Elimination durch Hämodialyse.

In 6 patients with no apparent kidney function the elimination of contrast medium was examined using 125I-labelled diatrizoic acid. Also blood level time curves and concentrations of dialysate were measured, showing a biexponential fall. The kinetic data established by computer-aided analysis according to the two-compartment model yielded elimination values not achieved by a healthy kidney; however a maximum elimination rate of 80.7 +/- 4.7% of the dose administered was calculated for a dialysis period of more than 10 hours. As the contrast medium plasma level was reduced the efficacy of haemodialysis fell.