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Description of key information

Taking into consideration the results of different studies done on animals and

especially on humans with the chelating agent HBED as well as physico-chemical properties and the available toxicity data on Fe(Na)HBED the conclusion can be taken that registered substance Fe(Na)HBED is not causing potential risk from toxicokinetic regime point of view including all absorption routes and no further tests should be continued or required. Fe(Na)HBED has low absorption potential via all exposure routes. If absorbed, it is expected to be distributed predominantly in intravasal compartment. The substance is not expected to be metabolised and will be excreted mainly unchanged via the faeces or via the urine. 10% absorption is considered for dermal and inhalation routes of exposure since physico-chemical characteristics of the substance are not in the ranges suggestive for extensive absorption into the body via these routes (TGD, Part I, 2003). 50% oral absorption is considered appropriate based on physico-chemical properties of Fe(Na)HBED as well as on the toxicity data obsrved in the oral studies conducted with the structurally related substance Fe(Na)EDDHA.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
Absorption rate - dermal (%):
Absorption rate - inhalation (%):

Additional information


Fe(Na)HBED is used as fertilizer against iron chlorosis in plants.

There are no ADME studies available for Fe(Na)HBED.The toxicokinetic profile of the test substance was not determined by actual absorption, distribution, metabolism or excretion measurements. Rather, the physical chemical properties of this substance were integrated with the available data from acute toxicity studies, irritation, sensitization and genetic toxicity studies to create a prediction of toxicokinetic behaviour (please refer to an extended version of “Assessment of toxicokinetic behaviour” attached to the IUCLID file under section 13). In addition, the data on repeated dose toxicity of the nearest analogues Fe(Na)EDDHA and Fe(Na)EDDHMA and the chelating agent HBED was taken into account to elucidate toxicokinetic behaviour of Fe(Na)HBED. The chelating agent HBED was investigated in a lot of pharmacological studies in animal test systems of iron overload as well as in patients with β-thalassemia. Once absorbed, HBED is dispersed through the body by bloodstream and able to bind to iron, producing FeHBED which is then excreted. So, the toxicity, side effects, distribution and excretion pattern of the chelating agent HBED are also related to its product Fe(Na)HBED. Therefore, the results of these studies are helpful for the assessment of toxicokinetics.

Toxicological profile of FeHBED

There are acute toxicity studies (oral and dermal), skin and eye irritation as well as skin sensitization studies available for the target substance Fe(Na)HBED. However, no studies are available for Fe(Na)HBED for repeated dose toxicity and for reproductive and developmental toxicity. Therefore read-across from structurally related substances Fe(Na)EDDHA (CAS 84539—55-9) and its methylated analogue Fe(Na)EDDHMA (84539-53-7) was performed. The related substances show very similar physical/chemical properties (high water solubility, low Pow, no hydrolysis in water) and are thus believed to behave very similar in aqueous solutions (please refer to read-across statement).

In the acute oral toxicity study according to OECD 420 and GLP, the LD50 in Wistar rats was determined to be greater than 2000 mg/kg bw (Gruszka, 2008a). No deaths and clinical signs were noted in treated animals. Bodyweight development was not impaired. An acute inhalation toxicity study with rats conducted with the related substance Fe(Na)EDDHA revealed a LC50-value of > 4200 mg/m³ (the highest technically achievable concentration) (CIBA-GEIGY, 1994a). In the acute dermal toxicity studies available for Fe(Na)HBED all animals survived a 24-hour dermal application in good health (Gruszka, 2008b). No skin changes, clinical signs or findings at necropsy were noted in the treated animals. The LD50 of 2000 mg/kg bw was determined. Fe(Na)HBED does not fulfil requirements to be classified as skin or eye irritant. Well defined erythema and very slight oedema were fully reversible in animals treated with Fe(Na)HBED in a skin irritation study according to the OECD Guideline 404 (Gruszka, 2008c). No pathological changes were observed in cornea of all animals treated with Fe(Na)HBED at all reading time points (Gruszka, 2008d).

In a skin sensitization study conducted with Fe(Na)HBED, allergic skin reactions were stated in 11 on 16 animals treated with Fe(Na)HBED, at the 48-hour and 72-hour reading time points after the start of challenge exposure, (Mrzyk, 2008). During reading after 48 hours since the end of exposure, discrete or patchy erythema was stated on skin of seven females; discrete or patchy eryhtema with dryness of epidermis were observed in one female. No pathological changes were stated in the remaining animals. No pathological changes were stated on skin of all animals in the site of medium application. During reading after 72 hours since the end of exposure discrete or patchy erythema was stated on treated area of skin of one female; discrete of patchy erythema with dryness of epidermis were observed in ten females. Therefore, F(NaHBED meets criteria for classification and labelling as skin sensitizer according to the Regulation (EC) No 1272/2008.

Fe(Na)HBED was not mutagenic in the Ames Test (Bednarikova, 2009). There are no further genetic toxicity tests available for Fe(Na)HBED. Its structural analogue Fe(Na)NaEDDHA was examined in three different in vitro genetic toxicity studies, all three with and without metabolic activation. The test item did not induce gene mutations by frameshift or base-pair substitution in the examined strains in the Ames test(CIBA-GEIGY, 1994c). Fe(Na)EDDHA tested up to cytotoxic concentrations did not induce structural chromosome aberrations in Chinese Hamster ovary cells and was therefore not considered clastogenic in the tested system (CIBA-GEIGY, 1994d). Finally, Fe(Na)EDDHA showed no mutagenic effect in a Mouse Lymphoma assay (CIBA-GEIGY, 1994b).

In a 90-day oral (gavage) repeated dose toxicity study in rats conducted with the related substance Fe(Na)EDDHA, a NOEL of 10 mg/kg bw/day was established based on a transient normochromic anaemia present at higher dose levels (Novartis Crop Protection AG, 1998). Changes in clinical laboratory parameters noted at higher dose levels and indicative of effects on kidneys and/or liver were without microscopic correlate under the conditions of this study. A supporting and preceding dose range finding sub-acute oral (gavage) toxicity study in rats provided further indication that the haematopoietic system and, at higher dose levels, the kidney represented target organs following repeated oral exposure (CIBA-GEIGY, 1996a).

In a subacute 28-day dermal toxicity study, a NOEL of 100 mg/kg bw was established based on slight effects on the liver and skin and due to increased adrenal weight noted at the high dose level of 1000 mg/kg bw/day (CIBA-GEIGY, 1996b). No data on repeated inhalation exposure are available.

In an one-generation reproduction toxicity study performed with the test item Fe(Na)EDDHMA (read across) in rats, the NOAEL of 200 mg/kg bw was established for reproductive performance/fertility based on a slight decrease in the conception indices and a minimal delay in precoital time noted at the high and systemically toxic dose level of 750 mg/kg bw/day (NOTOX, 1997). In agreement with the proposed read-across approach, this NOAEL is considered to represent a reliable key value for the chemical safety assessment of FeHBED.

In the key developmental oral toxicity study in rats with Fe(Na)EDDHA, a NOEL of 500 mg/kg bw/day, a systemically toxic high dose level, was established for developmental effects based on the absence of embryo-/foetotoxic or teratogenic effects (CIBA-GEIGY, 1995).


Toxicokinetic analysis of FeHBED

The substance Fe(Na)HBED is at 20 °C a brown solid microgranulate with a sweetish odour (MW of 463.2). The substance is soluble in water (34.55 g/L at 20°C13) and has a LogPow of -1.96. It has a very low vapour pressure (5.75 E-04 Pa at 20°C14). As already known from visual observations of the heating process, the melting and the decomposition of the test item start at ca. 250 °C. Hydrolysis as a function of pH does not apply as the substance forms extremely stable complexes. However, above pH 8, the stability is considerably reduced, despite that; hydrolysis is not expected, due to the lack of hydrolysable functional groups.


Oral absorption is favoured for molecules with MW below 500 g/mol. Based on the high water solubility and the very low logPow value, FeHBED is expected to be too hydrophilic to be readily absorbed from the gastrointestinal (GI) tract, but may be taken up by passive diffusion. However, absorption of very hydrophilic substances by passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. As the substance’s molecular weight is higher than 200, Fe(Na)HBED is very unlikely to pass through aqueous pores or be carried through the gastrointestinal epithelial barrier by the bulk passage of water. The read-across substances Fe(Na)EDDHA and Fe(Na)EDDHMA showed toxic effects at concentration as low as 50 mg/kg bw/day in repeated dose and reproduction toxicity studies when administered orally, respectively (Novartis Crop Protection AG, 1998;NOTOX, 1997). Administered in an acute study Fe(Na)HBED caused no mortalities up to the limit dose of 2000 mg/kg bw. Therefore, it can be assumed that only limited direct absorption across the gastrointestinal tract epithelium will occur when Fe(Na)HBED applied orally. This thesis is supported by experimental data in monkeys obtained with the chelating agent HBED, which clearly demonstrate that oral administered HBED (if not incorporated into liposomes) was not effective in increasing iron elimination from the body (Bergeron et al., 1999). In contrast, parenteral administered HBED increased iron elimination. Based on molecular structure, molecular weight, water solubility, octanol-water partition coefficient as well as on the oral toxicity observed in repeated dose toxicity studies, it can be expected that oral absorption is moderate and therefore set to 50%.

Based on the low vapour pressure of < 5.75 E-04 Pa inhalation exposure is not likely. No particles with diameter under 100 µm were present by dry sieve granulometric method (Stefaniak, 2012). Moreover, the final product has a granulated form. Thus, it is very unlikely, that considerable amounts of the substance reach the lung. Nevertheless, if the substance reaches the lung, it is not very likely that the substance is taken up rapidly. Although it is very water-soluble substance but its molecular weight is 463.2 and therefore it might not be absorbed extensively through aqueous pores. Rather, the substance is expected to be diffuse/dissolve into the mucus lining the respiratory tract. The negative LogPow points also to a low potential to be absorbed across the respiratory epithelium.The related substance Fe(Na)EDDHA showed no toxic symptoms in rats after inhalation of 4200 mg/m³ in an acute inhalation toxicity study (CIBA-GEIGY, 1994a). Together, this indicates a low systemic availability after inhalation and if bioavailable, no toxicity effects via this route of administration. 10% inhalation absorption is considered appropriate since phisyco-chemical characteristics of the substance are not in a range suggestive of favorable absorption from the respiratory tract.

Similarly, based on physico-chemical properties of Fe(Na)HBED, the substance is not likely to penetrate the skin to a large extent as the very low logPow value of <–1.96 and water solubility of 34,550 mg/L suggest that a substance is not likely to be sufficiently lipophilic to cross the stratum corneum. A water solubility above 10,000 mg/L together with the log P value below 0 further indicate that the substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum. Dermal uptake for these substances will be low. The molecular weight of 463.26 indicates already a low potential to penetrate the skin. This is supported by the findings of the low systemic toxicity of Fe(Na)HBED after exposure via the skin (acute dermal toxicity study, no mortality after dermal application of 2000 mg/kg bw in rats (Gruszka, 2008a). Moreover, an acute dermal irritation / corrosion study in the rabbit (according to OECD 404) for Fe(Na)HBED did not demonstrate any irritation after 14 days (Gruszka, 2008b). This information indicates that Fe(Na)HBED is unlikely to penetrate the skin. Furthermore, application of the structural analogue Fe(Na)EDDHA to the skin of rats in a dermal 28-day repeated dose toxicity study did cause only slight systemic effects on body and adrenal weight at the dose of 1000 mg/kg bw/day, supporting the limited bioavailability via this route. According to TGD, Part I (2003), 10% of dermal absorption is considered for Fe(Na)HBED, due to the high water solubility of 34,550 mg/L and logPow of -1.96. Although MW is slightly under 500 but taken into account the very high water solubility, 10% of dermal absorption is more appropriate for this substance.

Distribution and accumulative potential

Due to minor absorption, only a limited amount of Fe(Na)HBED is expected to be available for distribution. However, the minor amount absorbed into the body, will most likely distribute only in the intravascular compartment (due to its high molecular weight and the low LogPow) and will not reach the inner cell compartment, as the cell membranes require a substance to be soluble also in lipids to be taken up. As it is known that “substances with LogPow values of 3 or less would be unlikely to accumulate with the repeated intermittent exposure patterns normally encountered in the workplace”, no enhanced risk for accumulation will be associated with the substance, due to its low LogPow of -1.96.
Liang and colleagues showed that systemic administration of chelating agent HBED (subcutaneously) in rats resulted in its penetration through the blood brain barrier and its accumulation in hippocampal mitochondria, remaining 25% of the peak values until 24 hours after the administration (Liang, 2008). Total iron levels in the hippocampus were decreased. However, no conclusion can be made whether or not the target substance Fe(Na)HBED will penetrate blood brain barrier. These results endorse the assumption that Fe(Na)HBED, the corresponding substance to the chelating agent HBED, is expected to be distributed mainly in the body fluids.

Metabolism and excretion

Based on the structure of the molecule and its nature, metabolism in the human body will mainly consist on phase-II metabolising steps. Glucuronidation is one of such pathways leading to a better water solubility for excretion and might also occur in case of Fe(Na)HBED. This is in compliance with the results obtained in the Ames test conducted with the target substance Fe(Na)HBED as well as in the Chromosome Aberration Assay and in the Mouse Lymphoma Assay conducted with the analogue Fe(Na)EDDHA showing no effects with and without metabolising system. Metabolic activation leading to more toxic metabolites is thus not very likely.

Further, due to the high stability constant of the iron chelate complex (K = 10-39) it is clear that it exerts a low reactivity in the organism. Therefore, it is assumed that most of this iron fraction is excreted unchanged in the chelated form. Thus the already very water soluble native substance will be eliminated mainly in the faeces and to a lower extent in the urine. This thesis is supported by findings that HBED, investigated in Sprague Dawley rats overloaded with iron via intraperitoneal (i.p.) injections and per oral, induced iron excretion mainly via the stool (Grady and Herschko, 1990). In patients with β-thalassemia, HBED iduced iron excretion predominantly in the faces (Grady et al., 1994). In Cebus apella monkeys, HBED if administered subcutaneously caused additional iron excretion mainly in the stool (92%) and little elimination via the urine (8%) (Bergeron et al., 1998). In contrast, oral administration of HBED resulted in 56% iron excretion in the stool and about 44% in the urine (Bergeron et al., 1998). As the substance has a molecular weight above 300 g/mol the excretion of a considerable amount via the bile is also possible, especially if phase-II conjugation takes place e.g. with formation of glucoronid derivates. In this case the possibility of entero-hepatic recycling, and the risk of re-entering the system, but this does not enhance the risk for the organism.


Based on high water solubility, low octanol-water partition coefficient and low vapour pressure, Fe(Na)HBED is expected to be unlikely readily absorbed after oral exposure. This agrees with the high LD50 > 2000 mg/kg bw, determined in rats after oral exposure to Fe(Na)HBED. Concerning the absorption after exposure via inhalation, as the chemical has really low vapour pressure, it is clear, that the substance has a low availability for inhalation. Fe(Na)HBED is not expected to be absorbed significantly following dermal exposure into the stratum corneum, due to its molecular weight, its LogPow and its high water solubility. Accordingly, its systemic toxicity via the skin has been proven to be low (no mortality after dermal application of 2000 mg/kg bw in rats). The substance is not expected to bear accumulative potential. Fe(Na)HBED is not expected to be extensively metabolised but to be eliminated mainly via the bile (in cases as glucuronic acid conjugates) or, due to its high water-solubility to a smaller extent oxidised or unchanged via the urine. From the results of the toxicokinetics assessment it can be concluded, that uptake and resulting effects in the human body through all routes of exposure are negligible.

Literature data available on the chelating agent HBED (precursor of FeHBED)

In order to assess toxicokinetics behaviour of Fe(Na)HBED, pharmacokinetic studies conducted with its precursor (chelating agent HBED) were taken into account, since HBED, once absorbed, is capable to bind iron forming the target substance Fe(Na)HBED.

Liang and colleagues investigated the distribution of HBED in rats (Liang, 2008). Chelatable iron is an important catalyst for the initiation and propagation of free radical reactions and implicated in the pathogenesis of diverse neuronal disorders. Studies have shown that mitochondria are the principal source of reactive oxygen species production after status epilepticus (SE). It was investigated whether SE modulates mitochondrial iron levels and whether consequent mitochondrial dysfunction and neuronal injury could be ameliorated with a cell-permeable iron chelator. Kainate (KA) induced SE resulted in a time-dependent increase in chelatable iron in mitochondrial but not cytosolic fractions of the rat hippocampus. Systemically administered N,N-bis (2-hydroxybenzyl) ethylenediamine-N,N-diacetic acid (HBED), a synthetic, blood brain barrier permeable iron chelator, ameliorated SE-induced changes in chelatable iron, mitochondrial oxidative stress (8-hydroxy-2 deoxyguanosine and glutathione depletion), mitochondrial DNA integrity and hippocampal cell loss. HBED significantly attenuates SE induced hippocampal neuronal damage. Measurement of brain HBED levels (brain bioavailability of HBED after systemic administration, measured in forebrain tissue and hippocampal mitochondria) after systemic administration of 75 µmol/kg, s.c. confirmed its penetration in hippocampal mitochondria. HBED levels were detected 1 h after administration, peaked at 3 h and remained stable for at least 6 h. Moreover, both tissues and mitochondrial HBED levels remained 25 % of the peak values until 24 h after injection. These results suggest that HBED penetrates the blood brain barrier and is accessible to hippocampal mitochondria. Total iron levels in the hippocampus were decreased 30% after 4 or 5 daily injections with 75 µmol/kg HBED. Increasing the injection frequency to 7 resulted in a 38% reduction of iron content compared with control animals but retarded weight gain. These results suggest a role for mitochondrial iron in the pathogenesis of SE-induced brain damage and subcellular iron chelation as a novel therapeutic approach (neuroprotective effects of HBED by inhibition of SE induced mitochondrial oxidative stress) for its management. However, HBED’s inability to influence behavioural seizure parameters produced by KA suggests that its mechanism of neuroprotection is not related to interference with acute seizure initiation and a direct antioxidant action of HBED cannot be ruled out.

In a review the available information on the chelator HBED has been summarised (Grady and Hershko, 1990). The potential of HBED was first demonstrated using the hypertransfused rat model of iron overload. This model utilized female Sprague-Dawley rats overloaded with iron via intraperitoneal (i.p.) injections of heat-damaged rat erythrocytes. The chelator under investigation is administered daily at least 4 h after injection of the red cells. Urine and stool are collected daily for 5 days and their iron content determined by atomic absorption. When given parentally, HBED induced twice the net urinary iron excretion of an equivalent dose of desferrioxamine (DFO) and nearly three times the amount of stool iron. Total iron excretion was more than two and a half times that due to DFO. Upon oral administration. HBED retained approximately 25% of its activity, being 70% as effective as DFO given parenterally. HBED had no any effect upon the excretion of calcium, magnesium, copper, and zinc in the animals. Moreover, pharmacological studies of DFO, HBED and dimethyl ester (dmHBED) in rats (administration of 59Fe-ferritin-labelled hepatic parenchymal cells) were conducted via itramuscular injection. Urine and stool were collected daily for 6 days, after which the animals were sacrificed and residual radioactivity in their liver and spleen was measured, together with that in the accumulated urine and stool. None of the compounds caused significant change in the 59Fe content of urine or spleen. However, hepatic radioactivity declined in response to all drugs. HBED and dmHBED caused 63% and 80% of the respective amounts of total radioactivity to appear in the stool, compared to only 4 % in control animals. In a related study, 59Fe-labeled heat-damaged rat erythrocytes were injected, intravenously to label the reticuloendothelial system. Six days after labeling, 65% of the radioactivity in control animals remained in the liver and spleen and 6% was excreted spontaneously, roughly 90% of it in the stool. In response to intramuscular injection of DFO (200 mg/kg), there was a fourfold increase in excretion of radioactivity, the percentage in the urine increasing from 0.1% to 12.8%. Administration of equivalent doses of HBED and dmHBED led to a sevenfold increase in excretion, with more than 80% of the radioactivity appearing in the stool. There was an inverse relationship between the amount of radioactivity excreted and that which remained in the liver and spleen. That the ratio of splenic to hepatic radioactivity remained essentially constant following administration of HBED and DFO suggests that redistribution of iron from one tissue to another was not significant. The increased loss of hepatic radioactivity in response to dmHBED probably reflects differential tissue uptake of the diester rather than redistribution of iron. Residual radioactivity did not differ significantly from that in the case of HBED. The redistribution of iron was addressed with 59Fe-complexes injected sc into normal rats. Determination of cumulative excretion revealed a 94% excretion of the radioactivity bound to HBED compared to 84% to dmHBED and 75% for DFO. Thus, HBED can be expected to compete effectively with transferrin for iron, and causes preferential excretion of this iron rather than redistribution to other tissues. At low doses (25-50 mg/kg), HBED and dmHBED were 10-15 times more effective than DFO. Moreover, urinary excretion of radioactivity was never more than 4% of that administered, dmHBED having the greatest effect at all doses.

Chronic toxicity studies of HBED in mice, rats, and dogs showed a dose-related reduced growth in swiss-Webster mice (i.p. or oral administration for 10 weeks up to 200 mg/kg and 0.4% of the diet). The urine and stool of these animals were slightly reddish, due to the iron complex of HBED. Otherwise, the animals appeared healthy. At sacrifice, gross pathological examination revealed no evidence of toxicity.

When HBED (50, 100 and 200 mg/kg) was administered i.p. to female rats, all of the animals grew at a normal rate. In males, however, the growth was approximately 15% less than that of the controls at all doses (due in part to the fact that controls were not sham injected). At sacrifice none of the animals exhibited gross pathological abnormalities. The weight and appearance of liver, spleen, kidneys, adrenals, heart, lungs, testes / ovaries, and brain were normal. Histopathological examination revealed no drug-related lesions. The white cell count was slightly decreased in females, with the opposite effect being seen in males. Serum chemistries were essentially normal in both groups of rats. Thus, HBED given i.p. at doses up to 200 mg/kg/bw does not appear to result in significant toxicity. Oral administration of HBED doses up to 0.1% in diet had no significant effect upon the weight. At doses of 0.2% and 0.4%, however, decreased growth rates were observed. No gross or histopathological lesions were observed. The greatest changes were observed in the red cell indices (red cell count, haemoglobin, haematocrit, and mean corpuscular volume) of male rats were all significantly decreased in a dose-related manner. Reductions of 20% or more were observed with a dose of 0.4% HBED. Four weeks later, these indices were still depressed in a dose-related manner, but the reductions were less dramatic, indicating a partial resolution of the situation. Female rats exhibited similar changes. These changes, as well as the decreased growth rates, likely reflect a functional iron deficiency due to HBED-mediated inhibition of dietary iron absorption. That a haemolytic process was not responsible is indicated by the low-to-normal levels of splenic, hepatic, and marrow iron observed. Serum chemistries also exhibited a few abnormalities (not dose or time related; blood urea nitrogen (BUN), total bilirubin levels, serum glutamic-pyruvic transaminase (SGPT), serum glutamic-oxaloacetic transaminase (SGOT)). Finally, urinalyses were essentially normal, there being a slight shift to higher pH and lower specific gravity with increasing dose of drug.

Moreover, the toxicity of HBED was evaluated in beagle dogs at a dose of 100 mg/kg for six weeks. The animals all grew normally and experienced no known side effects. Their appetite was good, with no vomiting or diarrhoea observed. Serum chemistries and cellular blood profiles did not reveal any significant changes. An ophthalmologic examination after six weeks revealed no drug-related abnormalities. Likewise, there were no neurological deficits noted. At sacrifice, no gross or histopathological lesions were seen. The weight and appearance of the major organs were normal. In summary it can be stated, that HBED did not show a significant toxicity after parenteral or oral administration.

To examine the potential clinical usefulness of the hexadentate phenolic aminocarboxylate iron chelator N,N'-bis(2-hydroxybenzyl)ethylene- diamine-N,N'-diacetic acid (HBED) for the chronic treatment of transfusional iron overload (Bergeron, 1998), the iron excretion induced by subcutaneous (s.c.) injection of HBED and desferrioxamine (DFO), the reference chelator, in rodents and primates was compared. In the non-iron-overloaded, bile-duct-cannulated rat, a single s.c. injection of HBED, 150 µmol/kg, resulted in a net iron excretion that was more than threefold greater than that after the same dose of DFO. In the iron-loaded Cebus apella monkey, a single s.c. injection of HBED, 150 µmol/kg, produced a net iron excretion that was more than twice that observed after the same dose of s.c. DFO. Moreover, the LD50 (peroral or intraperitoneal) in rats is in excess of 800 mg/kg. In patients with transfusional iron overload, s.c. injections of HBED may provide a much needed alternative to the use of prolonged parenteral infusions of DFO.

The HBED-induced iron excretion was determined for the monohydrochloride dihydrate that was first dissolved in a 0.1-mmol/L sodium phosphate buffer at pH 7.6 and administered to the primates either orally (PO) at a dose of 324 μmol/kg (149.3 mg/kg), subcutaneously (s.c.) at a dose of 81 μmol/kg (37.3 mg/kg), s.c. at 324 μmol/kg, and s.c. at 162 μmol/kg (74.7 mg/kg) for 2 consecutive days for a total dose of 324 μmol/kg (Bergeron et al., 1999). In addition, the monosodium salt of HBED in saline was administered to the monkeys' s.c. at a single dose of 150 μmol/kg (64.9 mg/kg) or at a dose of 75 μmol/kg every other day for three doses, for a total dose of 225 μmol/kg. For comparative purposes, desferrioxamine (DFO) (reference chelate) was also administered PO and s.c. in aqueous solution at a dose of 300 μmol/kg (200 mg/kg). In the iron-loaded Cebus apella monkey, whereas the PO administration of DFO or HBED even at a dose of 300 to 324 μmol/kg was ineffective, the s.c. injection of HBED in buffer or its monosodium salt, 75 to 324 μmol/kg, produced a net iron excretion that was nearly three times that observed after similar doses of s.c. DFO. The majority of iron was excreted in the faeces. In patients with transfusional iron overload, s.c. injections of HBED may provide a much needed alternative to the use of prolonged parenteral infusions of DFO.