A brief history of toxicology in France during the last two centuries (1789-1989)

The history of toxicology in France over the last two centuries has been marked by numerous authors who have progressively broadened the fields of investigation: initially concerned with criminal or accidental poisonings, they have also taken an interest in the environment, workers' health, doping and illicit products, the dangers of radioactivity or combat gases, the risks associated with drugs, etc. Often pharmacists, these toxicology experts were specialists in analytical chemistry and developed numerous methods to refine the detection and characterization of potentially toxic products, and to better understand the mechanisms of toxicity produced by these substances.

Comparative Study of the Dialysability of Iobitridol and Iohexol in the Rat with Impaired Renal Function

Purpose:

To assess the dialysability of iobitridol, a comparative study with iohexol was conducted in the rat over 4 hours.

Material and Methods:

After ligature of the renal veins and arteries, a group of animals was submitted to continuous peritoneal dialysis, while the remainder were not.

Results:

In the event of total renal failure, biliary excretion rose from 0.4 to 9% for iobitridol and from 2 to 16% for iohexol. In the rats submitted to peritoneal dialysis, biliary excretion decreased to 5% in the iobitridol group and to 13% in the iohexol group. Further, 18% of the test substances were eliminated in the dialysis liquid.

Conclusions:

As their physicochemical characteristics are very similar, the differences between the biliary excretion levels of these 2 media may be caused by a factor related to their respective molecular conformations.

Effect of Contrast Media on Whole Blood Filtrability

The effects of three contrast media, iohexol, iopamidol and ioxaglate, on rat erythrocytes were compared. Three parameters representative of the rheologic properties of blood were investigated: whole blood filtrability, red cell filtrability and morphology. Whole blood and red cell filtrabilities were both measured using an erythrometer and red cell morphology was observed with an optical microscope. Iohexol and iopamidol were found to cause a significant increase in filtrability indices and to modify the shape of red blood cells. Ioxaglate had less effect on these parameters than did the other two contrast media. The chemical structure seems to be a determining factor for red cell integrity. The study of blood rheology parameters in vitro may be useful as a model predictive of observations on human blood and of hemodynamic consequences.

[Nanoparticles: the industrial viewpoint. Applications in diagnostic imaging]

Iron oxide particles can be divided into two categories: small superparamagnetic iron oxide (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO). Both describe nanoparticles most often formulated with dextran or dextran derivatives. For magnetic resonance imaging, these agents are of major importance because of their superparamagnetic effect, that is the magnetic field generated locally by their presence. Clinical applications have been well differentiated: 1) SPIO (larger than 50nm) are mainly used via intravenous infusion to detect and characterize small focal lesions in the liver. SPIO can also be given orally to visualize the digestive tract; 2) USPIO (smaller than 50nm) have a longer plasmatic half-life (>36hours) and exhibit slower uptake by liver and spleen after intravenous administration. This allows the product to access macrophages in normal (lymph nodes) or diseased tissue (multiple sclerosis, graft rejection, atheroma plaques, stroke, rhumatoid arthritis). They can also be used as biomarkers to evaluate the efficacy of treatments. In addition to routine clinical applications, these agents are also under investigation to improve diagnoses in oncological, inflammatory and degenerative as well as cardiovascular diseases (risk of atheroma plaques).

Bioavailability of oral vs intramuscular iodinated oil (Lipiodol UF) in healthy subjects

BACKGROUND

In order to fight against iodine deficiency, the essential cause of endemic goiter and cretinism, several health organizations promoted campaigns of iodinated oil (Lipiodol UF) administration using iodinated oil administered intramuscularly. However, it seems preferable to administer iodinated oil orally, as this is more appropriate and since the efficacy of this route has been demonstrated as well as for intramuscular route by controlled clinical trials.

OBJECTIVE

To assess the bioavailability of iodinated oil (Lipiodol UF) administered via two different administration routes and the safety profile of this agent.

DESIGN

A randomized bioavailability study was performed comparing a single oral dose of 3 capsules (570 mg of iodine) vs a single intramuscular injection of 1 ml of Lipiodol UF (480 mg of iodine) in 36 healthy subjects followed for 9 months.

RESULTS

The results show that, at these dosages, the 24 h urinary iodine values are above baseline for both oral and intramuscular administrations (im: >12 months/oral: 6 months) for prolonged period of time. In terms of safety, Lipiodol, administered by im injection or orally, did not induce any undesirable effects or any alteration of thyroid function tests in this study.

CONCLUSIONS

In conclusion, this study shows that im or oral administration of a single dose of Lipiodol provides a significant and prolonged iodine supplement. The results obtained confirm the possibility of protection of exposed populations after annual administration of an appropriate single oral dose, without inducing any clinical or laboratory adverse effects. The product, by either route of administration, has a prolonged efficacy in iodine-deficient subjects (im: 2-3 years/oral: 1 year).

[The Swiss Commission of Goiter of January 21, 1922]

The Swiss Commission of Goiter met for the first time the 21st of January, 1922 and has been the first step of an historical event in terms of Public Health: the first requirement for salt iodination for the prevention of goiter. The minutes of this commission as well as the following scientific publications until 1930 indicate that the debate was still very vigorous about this recommendation but mainly about the origin of goiter and the iodine dose to be used. This dose went progressively from less than 10 mg of iodine per kilo of salt to the present WHO recommendation of 20 to 40 mg of iodine per kilo of salt. Another key point was the strategy of implementation of iodine. Two complementary approaches were proposed and implemented: iodine supplement to children at school and iodized salt available for the whole population. One point seemed clear for everyone at that time: iodine was not the source of goiter. Later scientific studies have shown that iodine deficiency was indeed the origin of goiter and associated pathologies.

Safety and pharmacokinetics of p792, a new blood-pool agent: results of clinical testing in nonpatient volunteers

RATIONALE AND OBJECTIVES

To evaluate the safety and pharmacokinetics of P792, a new macromolecular blood-pool agent for magnetic resonance imaging (MRI), in nonpatient volunteers.

METHODS

This was a single blind, placebo-controlled, ascending-dose study in 32 healthy male volunteers, randomized to receive a single intravenous dose of P792 (0.0065, 0.013, 0.026, and 0.039 mmol/kg). The safety controls consisted of complete pre- and postdose physical examinations, measurement of vital signs, clinical laboratory investigations, and monitoring of adverse events (up to 22 days after injection). For pharmacokinetic analysis, the determination of P792 was performed using the ICP-MS technique for blood and urine samples up to 22 days.

RESULTS

No serious adverse events occurred during the study. There were no clinically significant changes in vital signs, or clinical laboratory findings. P792 blood half-life, distribution volume, and renal clearance are consistent with the definition of a rapid clearance blood-pool agent (RCBPA) as defined previously.

CONCLUSION

P792 appeared to be a safe and well-tolerated RCBPA in nonpatient subjects. Phase II studies will be conducted to evaluate the efficacy of the blood-pool agent for vascular, perfusion, and permeability imaging in MRI.

Carboxymethyldextran-A2-Gd-DOTA enhancement patterns in the abdomen and pelvis in an animal model

The aim of this study was to assess MR signal enhancement patterns of carboxymethyldextran (CMD)-A2-Gd-DOTA, a new macromolecular contrast agent, in the abdomen and pelvis of New Zealand white rabbits. Nine New Zealand white rabbits underwent MRI before and following injection of 0.05 mmol/kg body weight (bw) CMD-A2-Gd-DOTA (52.1 kDa), using turbo FLASH-, dynamic FLASH 60 degrees-, T1- and T2-weighted spin-echo and turbo spin-echo sequences up to 10 days p.i. Changes in blood and tissue signal intensities (deltaSI) and relaxation rates (deltaR1) were calculated. Differences between pre- and post-contrast MRI data were compared using the Scheffé test. CMD-A2-Gd-DOTA demonstrated significant blood-pool enhancement and significant tissue enhancement on T1-weighted images, whereas no significant signal changes were observed on T2-weighted images (P < 0.05). Kidney parenchyma, pelvis and bladder demonstrated a subsequent enhancement, resembling renal elimination of the majority of the contrast agent. Liver parenchyma demonstrated a slow, delayed decay of the contrast enhancement due to storage and biodegradation of larger subfractions of the contrast agent. All tissue signal intensities were back to baseline 10 days p.i. CMD-A2-Gd-DOTA is a new macromolecular contrast agent with blood-pool effect, significant signal enhancement of abdominal organs and pelvic bone marrow, partial storage in the liver and baseline tissue signal intensities by 10 days p.i.

[The discovery of Tenebryl, the first French uro-angiographic iodized hydrosoluble product]

Ténébryl was perfected in 1931 by Marcel and André Guerbet. For the company which bore their name and after the discovery of Lipiodol, this was the opportunity to explore a new area in radiology: intravenous urography. The discovery of this product is exemplary in a greater sense, since it contributed to opening the way to a new class of contrast products of which the majority today are iodized products. All the ingredients of industrial research are present here, from risk-taking to successful commercialization.

[Lipiodol therapeutic indications from 1901 to 1930]

Iodine and iodide used to be very successful drugs, sometimes at massive doses. Highly iodinated oil such as lipiodol from Lafay discovered in 1901 were part of expanding the therapeutic use of iodine for various pathologies such as syphilis, cardiovascular and respiratory diseases, leprosy, goiter... The present publication reviews unpublished documents and publications from 1901 to 1930 on lipiodol to give an overview of therapeutic indications for this agent and the rationale behind it. In some areas such as asthma, iodide was still in use until the eighties. Prevention and treatment of endemic goiter is the only remaining domain for the therapeutic usage of lipiodol. It is the only reason why this product is on the WHO essential drugs list.

[The history of Lipiodol (1901-1994) or How a medication may evolve with the times]

The history of Lipiodol, an iodized oil perfected in 1901 by Marcel Guerbet and Laurent Lafay, offers the example of a product with multiple indications which, initially destined for therapeutic usage, was later successfully turned to radiologic applications; then, sixty years later, returned to its initial purposes. This shows that (1) very often new products find usages which their developers never suspected; (2) research can extend beyond the original synthesis and commercialization of the product; (3) at some point research on a medication becomes multidisciplinary.

[Iodine usage about 1880 by Antoine de Finance's formulary]

After the discovery of iodine by Courtois in 1812, this metal was very much in vogue for all the XIXth century for the treatment of numerous diseases. Antoine de Finance (1846-1898), family physician, described iodine and iodine derivatives usage in his own formulary, following the usual contemporary references (Bouchardat, Dorvault). As for those references, iodine was useful for diseases as different as lung diseases, tumors and syphilis but he added angor. As opposed to Bouchardat that used more than 129 formulations for iodine and iodine derivatives, Antoine de Finance is limited to 6 of them. This trend of using iodine for medicine will continue after the XIXth century and will remain essential at the beginning of the XXth century with the discovery of stable iodinated oils such as Lipiodol created in 1901 and first used for syphilis. This therapeutic usage of iodine will remain until today for preventive and curative treatment of iodine deficiency disorders.

Hepatocyte-mediated transport to the bile of AMI-HS, a particulate contrast agent

RATIONALE AND OBJECTIVES

The elimination of hepatocyte-directed particulate contrast agents has not been studied in the same detail as particles eliminated mainly by the mononuclear phagocyte system. The aim of the present study was to elucidate the fate of these particles by a multidisciplinary approach.

METHODS

After intravenous injection of AMI-HS particles directed to the hepatocytes, rats were killed and cytological studies, by both electron microscopy and histochemistry, and spectroscopic studies of the bile were performed. The data were compared with a dynamic magnetic resonance study of the heart and liver.

RESULTS

The particles were rapidly cleared from the blood by Kupffer cells and hepatocytes and then found first in the vascular and later in the biliary pole of the hepatocytes. After 24 hours, a relaxometric characterization of the bile showed the presence of unchanged particles in the bile.

CONCLUSIONS

These results show the capacity of the liver to excrete unchanged AMI-HS particles directly into the bile.

Physicochemical and biological evaluation of P792, a rapid-clearance blood-pool agent for magnetic resonance imaging

RATIONALE AND OBJECTIVES

To summarize the physicochemical characterization, pharmacokinetic behavior, and biological evaluation of P792, a new monogadolinated MRI blood-pool agent.

METHODS

The molecular modeling of P792 was described. The r1 relaxivity properties of P792 were measured in water and 4% human serum albumin at different magnetic fields (20, 40, 60 MHz). The stability of the gadolinium complex was assessed. The pharmacokinetic and biodistribution profiles were studied in rabbits. Renal tolerance in dehydrated rats undergoing selective intrarenal injection was evaluated. Hemodynamic safety in rats and in vitro histamine and leukotriene B4 release were also tested.

RESULTS

The mean diameter of P792 is 50.5 A and the r1 relaxivity of this monogadolinium contrast agent is 29 L x mmol(-1) x s(-1) at 60 MHz. The stability of the gadolinium complex in transmetallation is excellent. The pharmacokinetic and biodistribution profiles are consistent with that of a rapid-clearance blood-pool agent: P792 is mainly excreted by glomerular filtration, and its diffusion across normal endothelium is limited. Renal and hemodynamic safety is comparable to that of the nonspecific agent gadolinium-tetraazacyclododecane tetraacetic acid. No histamine or leukotriene B4 release was found in RBL-2H3 isolated mastocytes.

CONCLUSIONS

The relaxivity of P792 at clinical field is very high for a monogadolinium complex without protein binding. The pharmacokinetic and biodistribution profiles are consistent with those of a rapid-clearance blood-pool agent. Its initial safety profile is satisfactory. Experimental and clinical studies are underway to confirm the potential of P792 in MRI.

Preclinical profile of the monodisperse iodinated macromolecular blood pool agent P743

RATIONALE AND OBJECTIVES

To summarize the chemical synthesis, physicochemical characterization, pharmacokinetic behavior, and biological evaluation of P743, a new macromolecular iodinated contrast medium.

METHODS

The synthesis and molecular modeling of the iodinated macromolecule P743 are described. The pharmacokinetic profile was established in rabbits and rats. Acute toxicity in mice, renal tolerance in normal rabbits, and renal tolerance in uninephrectomized, dehydrated rats undergoing selective intrarenal injection was evaluated. In vitro permeability effects on isolated mastocytes and on the coagulation pathways were carried out. Computed tomography vascular imaging was performed after intravenous injection of P743 (300 mg I/kg) in rabbits and compared with the nonspecific nonionic agent iobitridol.

RESULTS

P743 is a monodisperse, macromolecular iodinated contrast medium. In both rabbits and rats, P743 showed a pharmacokinetic profile consistent with that of a rapid-clearance blood-pool agent. Its diffusion through the endothelium was found to be low in vitro, thus confirming early confinement of this macromolecule, unlike nonspecific contrast media. In both species, P743 was excreted by glomerular filtration. Acute toxicity disclosed no mortality at the highest volume that could be injected into mice, leading to a median lethal dose greater than 8.9 g I/kg. Renal tolerance was found to be good in both euvolemic rabbits and uninephrectomized, dehydrated rats. No histamine or leukotriene B4 release was found on RBL-2H3 isolated mastocytes. P743 did not interfere with the coagulation pathways. Imaging experiments confirmed that P743 remains in the vascular compartment for a longer time than does iobitridol, thus allowing vascular enhancement that is twice as high as that of iobitridol in the recirculation phase.

CONCLUSIONS

The pharmacokinetic and imaging profiles of P743, a new, monodisperse, macromolecular blood-pool iodinated contrast medium, were consistent with those of a rapid-clearance blood-pool agent. Its initial safety profile is satisfactory. Further experimental imaging studies are required to define the clinical interest in such molecules.

Niosomes as carriers of radiopaque contrast agents for X-ray imaging

Non-ionic surfactant vesicles (niosomes) are considered as carriers of iobitridol, a diagnostic agent used for X-ray imaging. The niosomes, with a diameter between 150 and 175 nm, are prepared using the film-hydration method followed by sonication. These vesicles were obtained with appropriate mixtures of D-alpha tocopheryl polyethylene glycol 1000 succinate, polyoxyethylene glycol 4000 stearate, sorbitan monostearate, cholesterol and dicetylphosphate. Methods allowing the increase of the rate of encapsulation and the stability of the vesicles were carried out. In addition to the study of the formulation of the vesicles, the physico-chemical and morphological properties of the vesicles have been studied.

Physical, chemical, and biological evaluations of P760: a new gadolinium complex characterized by a low rate of interstitial diffusion

An original gadolinium chelate, termed P760, which diffuses through the vascular endothelium but at a much lower rate than nonspecific agents (NSA), is described. P760 is a gadolinium macrocyclic compound based on a DOTA structure that is substituted by hydrophilic bulky groups branched on the amino-carboxylic residues. The molecular weight is 5293, and the molecular volume, measured by light scattering, is 30 times higher (11.5 nm3) than that of gadolinium (Gd)-DOTA (0.38 nm3). The increase in molecular volume and weight has two consequences: a) higher relaxivity (r1; 24.7 mM-1.s-1 compared with 3.4 mM-1.s-1 for Gd-DOTA at 20 Mhz, 37 degrees C); and b) a lengthening of its transport rate through the endothelium. P760 presents a peculiar pharmacokinetic profile: at early times post injection, the blood concentrations are higher than those of Gd-DOTA, but after 20 minutes, the blood concentrations are equal for the two compounds. The body clearances of the products are identical (i.e., glomerular filtration rate). P760 molecules are large enough to have a restricted diffusion through the endothelium but, conversely, small enough to pass freely through the glomerular membrane. This limited extravasation has been observed in rabbits by magnetic resonance angiography or in investigations of tumor permeability. Further experimental imaging studies are needed to define the clinical interest of such properties.

P760 and P775: MRI contrast agents characterized by new pharmacokinetic properties

RATIONALE AND OBJECTIVES

In this paper we discuss novel MR imaging blood pool agents characterized by new pharmacokinetic properties.

METHODS

The pharmacokinetics of the products were studied in a rabbit model. The potential of these new products was demonstrated in experimental MR imaging.

RESULTS AND CONCLUSION

Three main classes of blood pool agents have been defined and characterized according to their pharmacokinetic properties: low diffusion agents, rapid clearance blood pool agents, slow clearance blood pool agents. Each kind of blood pool agent is expected to have different diagnostic applications.

Electron microscopy study of intrahepatic ultrasmall superparamagnetic iron oxide kinetics in the rat. Relation with magnetic resonance imaging

Ultrasmall superparamagnetic iron oxide (USPIO) contrast agents for use in magnetic resonance imaging (MRI) are currently undergoing clinical evaluation. However, the images observed and the kinetic profiles obtained differ from one agent to another. In this study, BD IX rats received an intravenous penis injection of the USPIO contrast agents AMI-HS and AMI-227. A cytologic study of the liver was performed, and the data obtained were compared with those of MRI. Images acquired in light microscopy, transmission electron microscopy, microanalysis and electron diffraction provided data on the cell categories involved in the processing of these contrast agents, the importance and modalities of each category relative to this processing, and the modalities of agent elimination. AMI-HS was rapidly removed from the bloodstream by Kupffer's cells and hepatocytes and then eliminated through bile ducts. AMI-227 remained much longer in the blood compartment since it was processed very slowly by endothelial and Kuppfer's cells in the near absence of hepatocytic participation and thus of elimination by the bile ducts. These results allowed us to base our interpretation of MRI sequences on cytologic observations.

Subcutaneous and intravenous delivery of diagnostic agents to the lymphatic system: applications in lymphoscintigraphy and indirect lymphography

Lymph node status is important in the staging of many malignancies. Although tissue characterization by histologic analysis of biopsy samples may improve staging, noninvasive staging is more acceptable to both patients and clinicians. Several imaging techniques may serve this goal. Modern noninvasive techniques such as computed tomography and magnetic resonance detect lymph node abnormality by nodal enlargement, but that does not always imply malignant involvement. On the other hand, many nodes are infiltrated or replaced by tumour without change in size. This becomes a serious diagnostic defect by these modalities. Consequently, attention has been focused to develop contrast agents and radiolabelled complexes for better cancer detection as well as characterization of individual tumours in lymph nodes. For delivery of such materials to regional lymph nodes one can take advantage from the distinct physiological function of the lymphatic capillaries. The thin-walled and fenestrated lymphatic microvessel is easily penetrated by particulate and macromolecular agents after injection into the extracellular space. Once inside the vessel, materials that are transported with the lymph either specifically target certain nodal elements (e.g. neoplastic cells) or become cleared by macrophages located in the lymph nodes. Indeed, interstitial delivery of diagnostic agents have been of benefit in determining regional spread of cancer and assessing lymphatic function either by lymphoscintigraphy or indirect lymphography. On the other hand, development of contrast materials that can reach lymph nodes after a single intravenous injection is highly desirable because of the large number of lymph nodes in the body and access being difficult to most of them. Today, a number of contrast agents exist that can reach a vast array of lymph nodes in the body, particularly those that are not readily accessible for histologic evaluation, after a single intravascular injection to help distinguish between normal and tumour-bearing nodes or reactive and metastatic nodes with magnetic resonance. In this article we critically examine advantages and limitations of both subcutaneous and intravenous routes of injection for the delivery of diagnostic agents to the lymphatic system.

Superparamagnetic agents in magnetic resonance imaging: physicochemical characteristics and clinical applications. A review

Superparamagnetic agents in magnetic resonance imaging: physico-chemical characteristics and clinical applications. Superparamagnetic agents have been the subject of extensive research over the last decade. They consist of iron oxide nanoparticles which are highly effective in Magnetic Resonance Imaging (MRI). The particle size varies widely and influences their physicochemical and pharmacokinetic properties. Their main present and future applications by the parenteral route are: imaging of gastrointestinal tract, liver and spleen, lymph nodes. Ultrasmall superparamagnetic iron oxide particles (USPIO) are also blood pool agents which could be used for perfusion imaging (i.e. brain or myocardial ischemic diseases) as well as for imaging of vessels in Magnetic Resonance Angiography. These agents open up an important field of research into more specific agents adapted to clinicians' needs in diagnostic imaging.

[Vascular contrast agents. Definition and potential applications]

Blood pool agents are characterized by a biodistribution limited to the vascular space after intravenous injection. This is different from uroangiographic agents in CT Scanner or Gd chelates in MRI which are markers for the intra and extravascular space. This unique property is potentially useful for diagnostic applications such as ischemic diseases (myocardial or cerebral perfusion defects), vascular diseases and diagnostic or follow-up of endothelial permeability disorders (diabetic patients, tumors...).

Role of sodium in contrast medium-induced polymorphic ventricular tachycardia: results in a rabbit model of lengthened QT interval

RATIONALE AND OBJECTIVES

The authors (a) compared the proarrhythmic effects of ioxaglate (152 mmol/L sodium) and iohexol (no sodium) in a rabbit model and (b) assessed the effect of adding 150 mmol/L sodium to isotonic iohexol.

MATERIALS AND METHODS

Either ioxaglate (320 mg of iodine per milliliter) or iohexol (350 mg of iodine per milliliter) was selectively injected into the right coronary artery (1.5 mL over 30 seconds) of 10 rabbits, some of which also received the alpha 1-adrenergic receptor agonist methoxamine. To validate the model, the class III antiarrhythmic agent clofilium was injected intravenously during methoxamine infusion. Frontal electrocardiography was performed continuously to detect polymorphic ventricular tachycardia (PVT). In a second study, the authors assessed the frequency of arrhythmias after injection of isotonic iohexol solution (145 mg of iodine per milliliter), either alone or with 150 mmol/L sodium.

RESULTS

Methoxamine significantly lengthened the QT, QTc, and RR intervals (P < .05). The use of clofilium alone induced no PVT, whereas five of eight methoxamine-infused rabbits developed PVT after clofilium injection (P = .03). Both contrast media prolonged the repolarization period. Iohexol alone induced a higher frequency of PVT than did ioxaglate alone (P = .0006). Methoxamine infusion did not potentiate the frequency of PVT in the ioxaglate-injected rabbits. The addition of sodium to isotonic iohexol prevented the occurrence of PVT (P = .0006).

CONCLUSION

Although ioxaglate prolonged the repolarization period, it did not cause a higher frequency of arrhythmia when injected in association with methoxamine. Iohexol, which contains no sodium, induced a high frequency of arrhythmia. The addition of a physiologic concentration of sodium to isotonic iohexol can prevent ventricular arrhythmias.

Structure-activity relationship of macrocyclic and linear gadolinium chelates: investigation of transmetallation effect on the zinc-dependent metallopeptidase angiotensin-converting enzyme

Transmetallation between commercially available solutions of gadolinium (Gd) chelates and the zinc (Zn)-dependent angiotensin-converting enzyme (ACE) was investigated. In vitro, the strongest inhibitions were observed for the linear Gd complexes, Gd diethylenetriamine pentaacetic acid (DTPA) bis-methylamide (BMA) (IC50 = .016 +/- .006 mmol/l) and Gd-DTPA (IC50 = .350 +/- .034 mmol/l). The two macrocycles Gd tetraazacyclododecane tetraacetic acid (DOTA) and Gd-HP-DO3A were similar and 400 times less active than Gd-DTPA-BMA. These effects were mainly due to the presence of free ligand for DTPA and calcium (Ca) chelate in the case of DTPA-BMA because the addition of Zn2+ in the same quantities suppresses their inhibitory effects. In vivo, these two solutions of linear Gd chelates significantly inhibited ACE activity (Gd-DTPA: (67 +/- 9% versus baseline; and Gd-DTPA-BMA: 73 +/- 2% versus baseline at the clinical dose of .1 mmol/kg), whereas no significant effect was observed for the two macrocyclic chelates Gd-DOTA and Gd-HP-DO3A. Formulating the Gd chelate solution with either an excess of free ligand or Ca chelate (to decrease Gd3+ release) in the case of linear Gd chelate may have deleterious biologic consequences.

Haemodynamic effects of macrocyclic and linear gadolinium chelates in rats: role of calcium and transmetallation

Several studies were undertaken to compare four magnetic resonance imaging (MRI) contrast media (CM) as regards acute haemodynamic effects in rats and to investigate the mechanisms involved. (1) Normotensive rats received a rapid bolus intravenous injection of 0.5 mmol kg-1 of each CM. The effects of Gd-DOTA, Gd-HP-DO3A, Gd-DTPA and Gd-DTPA-BMA on blood pressure (BP) were compared. (2) The haemodynamic effects of Gd-DTPA (0.5 mmol kg-1) were compared to those of isovolumic and isoosmolar Zn-DTPA and glucose solutions. (3) The haemodynamic profiles of Gd-DTPA and Gd-DTPA-BMA were recorded with and without addition of ionized calcium. (4) The mechanism of Gd-HP-DO3A-induced transient rise in BP was investigated by evaluating the effects of phentolamine or diltiazem pretreatment. For (1) the greatest drop in BP occurred following Gd-DTPA (a linear chelate) injection (-18 +/- 2% vs baseline, P < 0.01). Gd-DTPA-BMA, another lineate chelate, also induced a slight but significant reduction in BP (-8 +/- 2% at 45 s, P < 0.05). Gd-DOTA, a macrocyclic CM, had virtually no haemodynamic effects. For (2) the Gd-DTPA-induced drop in BP was greater than that of the osmolality-matched glucose control and lower than that of osmolality-matched Zn-DTPA. For (3) a transmetallation phenomenon versus free ionized calcium is possible in the case of both linear CM (Gd-DTPA and Gd-DTPA-BMA) since Ca2+ significantly reduced the CM-induced decrease in BP. For (4) a transient rise in BP was observed following Gd-HP-DO3A, another macrocyclic chelate, associated with a concomitant increase in stroke volume. This effect was antagonized neither by phentolamine nor by diltiazem. The decrease in BP following injection of Gd-DTPA or Gd-DTPA-BMA may not only be osmolality-related since (a) Gd-DOTA solution, whose osmolality is greater than that of Gd-DTPA-BMA, had a lesser effect, and (b) this hypotensive effect was corrected by a addition of ionized calcium. The transient Gd-HP-DO3A-induced rise in BP is probably the consequence of a positive inotropic effect.

Secretion in milk and transplacental transfer of two iodized oils, Lipiodol UF and Oriodol, in rabbits

Many countries in the world are inhabited by populations suffering from iodine deficiency. These populations are affected by serious diseases directly related to iodine deficiency. Iodized oil (Lipiodol UF or Oriodol) is routinely used orally or intramuscularly to treat these populations, including pregnant women. The experiments of the present study in gravid or lactating rabbits show that there is transplacental transfer of iodine and secretion of iodine in milk after administration of iodized oil and consequently an accumulation of iodine in the thyroid glands of the mother, the fetus and the neonate. The advantages of treating pregnant women with iodized oil in the populations concerned is thus confirmed. The oral route can be substituted by the intramuscular route.

Toxicologic profile of iobitridol, a new nonionic low-osmolality contrast medium

PURPOSE

The toxicologic profile of iobitridol, a new nonionic low-osomolality contrast medium, was evaluated in compliance with the current regulatory requirements in Europe, the USA and Canada.

MATERIAL AND METHODS

The toxicity of iobitridol was tested following acute or repeated i.v. administration in several different species (mouse, rat, dog); single oral administration in the mouse and intracisternal injection in the rat. Furthermore, teratogenicity and mutagenicity were evaluated in the rat and rabbit. Local perivenous toxicity was assessed in the rabbit.

RESULTS

The acute toxicity of iobitridol in the mouse is equivalent to that of iohexol, a reference product tested under the same conditions. Chronic administration (daily injections i.v. injection over 4 weeks) in the rat and dog did not demonstrate any particular toxicity for iobitridol. It should be noted that, unlike iohexol, iobitridol did not provoke any vacuolization of the renal tubular cells in the rat following repeated injections. Furthermore, this contrast agent did not show any teratogenic or mutagenic potential. The typical local inflammatory signs observed following perivenous injection in the rabbit were low in intensity and reversible.

CONCLUSION

The toxicologic profile of iobitridol appears to be favorable and does not show any particular risk for clinical use under the usual indications of water soluble iodinated contrast agents.

Comparative study of the dialysability of iobitridol and iohexol in the rat with impaired renal function

PURPOSE

To assess the dialysability of iobitridol, a comparative study with iohexol was conducted in the rat over 4 hours.

MATERIAL AND METHODS

After ligature of the renal veins and arteries, a group of animals was submitted to continuous peritoneal dialysis, while the remainder were not.

RESULTS

In the event of total renal failure, biliary excretion rose from 0.4 to 9% for iobitridol and from 2 to 16% for iohexol. In the rats submitted to peritoneal dialysis, biliary excretion decreased to 5% in the iobitridol group and to 13% in the iohexol group. Further, 18% of the test substances were eliminated in the dialysis liquid.

CONCLUSIONS

As their physicochemical characteristics are very similar, the differences between the biliary excretion levels of these 2 media may be caused by a factor related to their respective molecular conformations.

High-performance liquid chromatographic determination of iobitridol in plasma, urine and bile

Iobitridol is a new non-ionic, low-osmolality contrast medium for urography and angiography. We have developed a method for determining iobitridol in body fluids using high-performance liquid chromatography with ultraviolet detection. The method, which is specific and reproducible, does not require an internal standard. Determinations can be carried out in body fluids against a set of standards in ethanol. The method was validated for the quantification of iobitridol in biological samples obtained during pharmacokinetic studies.

[Electrocorticographic evaluation of the neurologic tolerability of iobitridol (Xenetix), a new non-ionic contrast medium in rabbits]

Electro-corticographic tracings (two longitudinal leads, bipolar assembly) were recorded from curarized rabbits (5/group) receiving selective internal carotid artery injections of either iobitridol, a new non-ionic contrast medium, or iohexol, the high osmolar diatrizoate or hypertonic mannitol (isotonic to the non-ionic agents). A further group was submitted to the surgical preparation but was not injected. The solutions were injected at a dose of 2.5 ml during 30 seconds. The animals were anaesthetized (halothane) during the surgical period. The permeability of the blood-brain barrier was assessed by means of the extravasation of Evans'blue. Tracings were visually assessed and a semi-quantitative method for blind evaluation of fast/slow rhythms was used. This method was pharmacologically validated by the use of pentobarbital and pentylenetetrazole. Diatrizoate and iohexol induced respectively 3 and 2 paroxystic tracings during or immediately after the injection period. Iobitridol and hypertonic mannitol did not cause such effect. Paroxystic tracings in the iohexol group were not associated with extravasation of Evans'blue in the cerebral parenchyma. Blood brain barrier was disrupted in all rabbits receiving the high osmolar agent diatrizoate. Tracings of the control group were characterized by a progressive increase of fast rhythms, as those of the iobitridol and mannitol groups. On the contrary, iohexol and especially diatrizoate induced an increase in the proportion of slow waves. Taken together, these data suggest that iobitridol shows an excellent tolerability potential for clinical use.

Transplacental passage and milk excretion of iobitridol

RATIONALE AND OBJECTIVES

Iobitridol, a new nonionic, low-osmolality urographic and angiographic contrast medium, is a marker of extracellular fluid. Excretion of iobitridol in goat's milk and transplacental passage in the gestating rabbit were evaluated compared with iohexol.

METHODS

Both products were determined in biologic samples by two analytic methods: ultraviolet spectrometry (milk) and high-pressure liquid chromatography (maternal and fetal blood and amniotic fluid).

RESULTS

Excretion in the milk represents 0.7% of the administered dose for iobitridol and 1.6% for iohexol. Transplacental passage is nonexistent. Iobitridol and iohexol behave in a similar manner.

CONCLUSIONS

These preclinical results allow more effective prediction of the safety of iobitridol in pregnant or lactating women. However, precautions for use must be respected in the absence of specific studies in this population group.

Iobitridol, a new nonionic low-osmolality contrast agent, and iohexol. Impact on renal histology in the rat

RATIONALE AND OBJECTIVES

To compare the histologic effects on rat tubular cells of two nonionic contrast media with equivalent osmolalities and viscosities.

METHODS

Histologic, functional (creatinine clearance), and biochemical (proteinuria and enzymuria) profiles of iohexol and iobitridol (both at 350 mg I/mL) were compared in the uninephrectomized rat. A control group (n = 14) received compared isotonic saline solution. Test substances (3 mL) were injected into the kidney at a rate of 1 mL/minute while transitory ischemia was induced by clamping the aorta above the renal artery.

RESULTS

In terms of their (moderate) effects on creatinine clearance, proteinuria, and urinary N-acetyl-beta-D-glucosaminidase activity, no statistically significant difference was detected between the two low-osmolar contrast agents either 24 or 48 hours after injection. However, blinded histologic analysis of the kidneys showed significantly greater epithelial cell vacuolization in the proximal convoluted tubules of the outer cortex with iohexol (14 of 14 rats versus 3 of 14 rats for iobitridol; P < .001). The same degree of vacuolization in the inner cortex was observed for all three substances. Iobitridol also induced fewer congestive lesions in the glomerular capillaries than iohexol (4 of 14 versus 10 of 14, respectively; P < .05) and saline (5 of 6; P < .05). It is difficult to explain the lesser degree of cytoplasmic vacuolization using standard physicochemical parameters.

CONCLUSION

Although iobitridol and iohexol showed similar functional and biochemical profiles when selectively injected into the single remaining kidney of rats, iobitridol induced significantly less tubular vacuolization and capillary congestion than iohexol.

Comparative effects of low- and high-osmolar contrast media on the renal function during early degenerative gentamicin-induced nephropathy in rats

The nephrotoxic potentials of a high-osmolar contrast medium, diatrizoate, and of a low-osmolar contrast medium, ioxaglate, were compared during early degenerative gentamicin-induced nephropathy in the rat. Male rats (13-22/group) were uninephrectomized. Six days later, the aorta was clamped above the renal artery, and either diatrizoate or ioxaglate was administered (1 ml/min for 3 min) via an aortic puncture into the remaining kidney. Some of the rats received chronic treatment with gentamicin (50 mg/kg/day i.m., 4 days), starting 2 days before and ending 1 day after contrast medium administration. Two control groups, only one of which received gentamicin, were subjected to a 3-min renal ischemia. The creatinine clearance (CrCl) per 100 g body weight was determined before and 24 and 48 h after contrast medium injection. A second study (6 rats/group) evaluated urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion and the histologic appearance of the kidneys (blinded analysis) in the same experimental groups. Gentamicin induced a significant decrease in CrCl at baseline (0.35 +/- 0.19 vs. 0.41 +/- 0.19 ml/min; p < 0.01) and an increase in urinary NAG (128 +/- 92 vs. 39 +/- 57 mumol/h/mmol creatinine; p < 0.01). Taking into account these differences at baseline, univariate repeated-measures analysis showed that on day 1 diatrizoate caused a more marked decrease in CrCl than ioxaglate (p < 0.05), whether or not gentamicin was also administered. On day 2, the depressant effect of diatrizoate associated with gentamicin persisted (CrCl vs. day 0 = -0.19 +/- 0.10 ml/min), while that of diatrizoate alone returned to baseline (-0.05 +/- 0.24 ml/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Isolated Richter's syndrome of the brain: two recent cases

Two new cases of central nervous system (CNS) large cell lymphoma without evidence of systemic lymphoma in patients with chronic lymphocytic leukaemia (CLL) are reported. This unusual presentation of Richter's syndrome emphasizes the necessity to evoke this diagnosis in the case of neurologic symptoms in CLL.

Iodinated contrast media-induced nephropathy: pathophysiology, clinical aspects and prevention

Administration of iodinated contrast media (CM) for radiographic purposes is a preoccupying cause of acute renal failure. This review of the literature deals with what is known about physiopathology, clinical course, risk factors and prevention. Factors involved in the pathophysiology of CM-induced acute renal failure are vasoconstriction, direct tubular cell injury and tubular obstruction by casts. In the case of pre-existing renal hypoperfusion, CM may disturb the complex interaction between factors which modulate renal haemodynamics by increasing vasoconstrictor factors, notably endothelin peptides. The renal medulla, a zone characterized by a high metabolic activity and a low oxygen tension, may be a specific target for CM-induced effects. CM-induced nephropathy (CMN) is essentially observed in patients with one or more associated risk factors (chronic renal failure, dehydration, diabetes mellitus with impaired renal function, multiple myeloma, large CM volume, intra-arterial rather than intravenous route, etc). There is much debate as to whether newer low osmolar CM (LOCM) are better tolerated than conventional high osmolar CM (HOCM). Most of the animal studies clearly demonstrate the advantages of LOCM over HOCM. Clinical literature is far more confusing, although some recent studies and one meta-analysis demonstrate that LOCM are better tolerated in patients with impaired renal function. The low number of comparative clinical trials carried out in high risk patients, wide variability in CMN definitions, limited number of patients enrolled and inadequacy of various selected endpoints may explain difficulties experienced in demonstrating this advantage. Furthermore, while hydration is correctly maintained during clinical trials, this is not always true in clinical practice. Such a discrepancy could lead to underestimation of the potential advantage of LOCM over HOCM. Effective prevention should associate the correct hydration of patients, identification and, when possible, optimal correction of risk factors, avoidance of repeated CM injections within a short period of time and temporary disruption of treatment with other nephrotoxic drugs (non steroidal antiinflammatory drugs, aminoglycosides, etc).

Modulation of the renal effects of contrast media by endothelium-derived nitric oxide in the rat

RATIONALE AND OBJECTIVES

A possible involvement of endothelium derived relaxing nitric oxide (NO) in the pathogenesis of iodinated contrast media (CM)-induced nephrotoxicity was investigated in the rat.

METHODS

Male rats (6 to 12 per group) were uninephrectomized. Six days later, the aorta was clamped above the renal artery and a low-osmolar contrast medium (CM), ioxaglate, was injected (1 mL/min; 3 minutes) via an aortic puncture in the single remaining kidney. Contrast medium was injected with or without the NO-synthase inhibitor L-NAME (100 mg/kg intravenously [i.v.] 5 minutes before CM). One group received L-Arginine, the physiological precursor of NO (100 mg/kg i.v.), 5 minutes before L-NAME. Phenylephrine (300 micrograms/kg; 30 min) was used as a vasoconstrictive NO-independent control. The effects of iohexol, another low-osmolar CM, on creatinine clearance (CrCl) were also studied with and without pretreatment with L-NAME. A control group was subjected to a 3-minute renal ischemia only. Creatinine clearance and urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion were determined before, and 24 and 48 hours after CM administration. Blinded histologic analysis was carried out after completion of the study.

RESULTS

When administered alone, neither L-NAME nor L-arginine modified CrCl. Ioxaglate mildly but significantly decreased CrCl at 24 hours (-26.5% of preinjection value). This was similar to the effect observed in the control group subjected to ischemia only. When associated with L-NAME, ioxaglate markedly decreased CrCl (-58 + 11% at 24 hours, P < .05 vs. ioxaglate alone). A similar interaction was noted in the case of iohexol. L-NAME also markedly increased ioxaglate-induced urinary NAG excretion. Phenylephrine had a similar impact on renal function. L-arginine pretreatment reduced the increase in serum creatinine induced by L-NAME+ioxaglate (68 + 17 mumol/L vs. 175 + 59 mumol/L for L-NAME+ioxaglate; P < .05) and urinary NAG excretion. Ioxaglate alone induced only tubular epithelial vacuolization. When associated with L-NAME, this CM induced tubular and vascular lesions, as well as necrosis in the outer medulla. Such histologic effects were clearly inhibited by L-arginine.

CONCLUSION

These data indicate that L-NAME, a specific inhibitor of NO-synthase, and phenylephrine, accentuate the nephrotoxicity of CM in the rat. This is consistent with results from the literature showing that CM-toxicity is enhanced by renal ischemia.