Mercury kinetics in a case of severe mercuric chloride poisoning treated with dimercapto-1-propane sulphonate (DMPS)

Acute intranasal intoxication with mercuric chloride taken accidently instead of cocaine - A case report

CONTEXT

Mercuric chloride (mercury (II) chloride) belongs to inorganic mercury compounds characterized by good water solubility and associated high toxicity. The paper describes an unusual case of intranasal intoxication with corrosive sublimate confused with cocaine by a young male.

CASE REPORT

Intranasal administration of corrosive sublimate caused severe local symptoms of chemical burn within the nasal cavity. From the 2nd day the patient developed symptoms of renal dysfunction with transient polyuria and serum retention of nitrogen metabolites. The patient was undergoing chelation therapy with DMPS, N-acetylcysteine and d-penicyllamine. Four procedures of haemodialysis were performed with simultaneous DMPS and N-acetylcysteine treatment. The urine mercury level on the first day of hospitalization was 1989 μg/L, and after 26 days of treatment returned to the physiological level. During treatment renal function was normalized, the patient was discharged in general good condition.

DISCUSSION

Mercuric chloride is readily absorbed from the nasal cavity. Its administration may cause intoxication manifested by both chemical burn at the exposure site and systemic symptoms, particularly renal impairment. Even in case of renal dysfunction the use of DMPS seems safe, if haemodialysis is performed at the same time. Simultaneous haemodialysis and chelation therapy may accelerate elimination of mercury from the organism.

MEIC Evaluation of Acute Systemic Toxicity

The Multicenter Evaluation of In Vitro Cytotoxicity (MEIC) programme was set up to evaluate the relevance for acute human systemic toxicity of in vitro cytotoxicity tests. At the end of the programme in the summer of 1996, 29 laboratories had tested all 50 reference chemicals in 61 cytotoxicity assays. As a necessary prerequisite to the forthcoming evaluation papers of this series, this paper presents the animal and human toxicity data of the programme. This database contains tabulated handbook data for the 50 chemicals, on: a) oral rat and mouse LD50 values; b) acute oral lethal doses in humans; c) clinically measured acute lethal serum concentrations in humans; d) acute lethal blood concentrations in humans measured postmortem; e) peaks from curves of an approximate 50% lethal blood/serum concentration over time after ingestion (LC50 curves), derived from a compilation of human acute poisoning case reports; f) human kinetics of single doses, including absorption, peak time, distribution/elimination curve, plasma half-life, distribution volume, distribution to organs (notably brain), and blood protein binding; and g) qualitative human acute toxicity data, including lethal symptoms, main causes of death, average time to death, target organs, presence of histopathological injury in target organs, presence of toxic metabolites, and known or hypothetical mechanisms for the lethal toxicity. The rationales for selection of the human toxicity data are also noted. The methods used to compile the in vivo toxicity data are described, including a presentation of a new method of constructing LC50 curves. Finally, the merits and shortcomings of the various human toxicity data for evaluation purposes are discussed.

Lead, Mercury and Cadmium in Fish and Shellfish from the Indian Ocean and Red Sea (African Countries): Public Health Challenges

The main aim of this review was to assess the incidence of Pb, Hg and Cd in seafood from African countries on the Indian and the Red Sea coasts and the level of their monitoring and control, where the direct consumption of seafood without quality control are frequently due to the poverty in many African countries. Some seafood from African Indian and the Red Sea coasts such as mollusks and fishes have presented Cd, Pb and Hg concentrations higher than permitted limit by FAOUN/EU regulations, indicating a possible threat to public health. Thus, the operationalization of the heavy metals (HM) monitoring and control is strongly recommended since these countries have laboratories with minimal conditions for HM analysis.

Mercuric chloride poisoning: symptoms, analysis, therapies, and autoptic findings. A review of the literature

Among mercury-related intoxications, the re-emerging of mercuric chloride poisoning has been recently described in literature. Only sparse data, reporting the clinical symptoms, the anatomo-pathological findings, the analytical procedures or the treatment have been published and no exhaustive analysis of all these factors exists in literature. The classic symptoms associated with toxicity of mercuric chloride is a combination of renal, gastrointestinal (GI) and central nervous system (CNS) damages, eventually leading to death. Fatalities related to exposure to mercuric chloride have been reported since the nineteenth century. To date, there have been 45 published cases in the medical literature in which the intoxication or the death is attributed to mercuric chloride. In this review, we will describe the modern medical treatments, with particular attenztion to the developments of the lasts two decades, in order to provide an exhaustive description of the clinical symptoms, the post-mortem findings, and the analytical procedures to act out when mercuric chloride intoxication occurs. The analysis of the data obtained permitted us to accurately describe all the organs and apparatus involved in mercuric chloride intoxication. The target organs were the kidneys, the GI tract and the CNS. A description of the analytical procedures for the determination of mercuric chloride in biological materials, to carry out in vivo and in post-mortem samples has also been described.

Chelation therapy in intoxications with mercury, lead and copper

In the present review we provide an update of the appropriate use of chelating agents in the treatment of intoxications with compounds of mercury, lead and copper. The relatively new chelators meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercapto-propanesulphonate (DMPS) can effectively mobilize deposits of mercury as well as of lead into the urine. These drugs can be administered orally and have relatively low toxicity compared to the classical antidote dimercaptopropanol (BAL). d-Penicillamine has been widely used in copper overload, although 2,3-dimercaptosuccinic acid or tetrathiomolybdate may be more suitable alternatives today. In copper-toxicity, a free radical scavenger might be recommended as adjuvant to the chelator therapy.

Full recovery from a potentially lethal dose of mercuric chloride

INTRODUCTION

Mercuric chloride poisoning is rare yet potentially life-threatening. We report a case of poisoning with a potentially significant amount of mercuric chloride which responded to aggressive management.

CASE REPORT

A 19-year-old female presented to the Emergency Department with nausea, abdominal discomfort, vomiting of blood-stained fluid, and diarrhea following suicidal ingestion of 2-4 g of mercuric chloride powder. An abdominal radiograph showed radio-opaque material within the gastric antrum and the patient's initial blood mercury concentration was 17.9 μmol/L (or 3.58 mg/L) at 3 h post-ingestion. Given the potential toxicity of inorganic mercury, the patient was admitted to the intensive care unit and chelation with dimercaprol was undertaken. Further clinical effects included mild hemodynamic instability, acidosis, hypokalemia, leukocytosis, and fever. The patient's symptoms began to improve 48 h after admission and resolved fully within a week.

DISCUSSION

Mercuric chloride has an estimated human fatal dose of between 1 and 4 g. Despite a reported ingestion of a potentially lethal dose and a high blood concentration, this patient experienced mild to moderate poisoning only and she responded to early and appropriate intervention. Mercuric chloride can produce a range of toxic effects including corrosive injury, severe gastrointestinal disturbances, acute renal failure, circulatory collapse, and eventual death. Treatment includes close observation and aggressive supportive care along with chelation, preferably with 2,3-dimercapto-1-propane sulfonate or 2,3-meso-dimercaptosuccinic acid.

Toxicokinetics of mercury elimination by succimer in twin toddlers

We describe the toxicokinetics of mercury in two twin toddlers poisoned by an East Indian remedy for teething. Succimer (dimercaprosuccinic acid, DMSA) decreased the plasma elimination half-life of mercury by 3-fold in the patient with high exposure; a more modest effect was observed in the other twin. Succimer is a chelation agent used in the treatment of heavy metal intoxication. A water-soluble agent, it increases the urinary excretion of lead and mercury. The drug is rapidly but variably absorbed through the gastrointestinal tract, with peak levels occurring at 1-2 hours. After its absorption, peak mercury excretion through the urine occurs within 2-4 hours. In the poisoned twin sisters, succimer administration led to a mercury plasma elimination half-life of 6 weeks. Although succimer has been used in mercury poisoning in adults and children, the toxicokinetics of mercury have not previously been characterized in either age group. We believe this is the first such description. More studies on the toxicokinetics and dynamics of mercury chelation with succimer in young children are needed to ensure the optimal use of the drug in this population.

Ebselen protects glutamate uptake inhibition caused by methyl mercury but does not by Hg2+

Alterations of the neurotransmitter release systems in CNS have been reported in a variety of neuropathological processes associated with heavy metal toxicity. Neurotoxic effects of mercurials were investigated in vitro in cerebral cortex slices from young rats. The present study indicates that: (i) the environmental contaminants methylmercury (MeHg) and mercuric chloride (Hg2+) (50 microM) inhibited the glutamate net uptake from the cerebral cortex of 17-day-old rats; (ii) ebselen (10 microM) reverted the MeHg-induced inhibition of glutamate net uptake but did not protect the inhibition caused by Hg2+. At same time, we investigated another diorganochalcogenide, diphenyl diselenide (PhSe)2 and it was observed that this compound did not revert the action of MeHg or Hg2+; (iii) in addition, we observed that exposure of slices to 50 microM MeHg and Hg2+ for 30 min followed by Trypan blue exclusion assay resulted in 58.5 and 67.5% of staining cells, respectively, indicating a decrease in cell viability. Ebselen protected slices from the deleterious effects of MeHg, but not of Hg2+ on cell viability. Conversely, ebselen did not modify the reduction of MTT caused by MeHg and Hg2+; (iv) the protective effect of ebselen on MeHg-induced inhibition of glutamate net uptake seems to be related to its ability in maintaining cell viability.

2,3-Dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase mercury- and cadmium-induced inhibition of delta-aminolevulinate dehydratase

Compounds derived from Dimercaprol, such as meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS), are becoming common agents for treating humans exposed to heavy metals. Heavy metals such as Pb(2+), Hg(2+) and Cd(2+) can inhibit delta-aminolevulinate dehydratase (delta-ALA-D) activity. Delta-ALA-D catalyzes the condensation of two delta-aminolevulinic acid (delta-ALA) molecules with the formation of porphobilinogen, a heme precursor. The effects of DMSA and DMPS alone or in combination with Cd(2+), Hg(2+), or Pb(2+) on hepatic delta-ALA-D were examined. DMPS and DMSA caused a dose-dependent inhibition of hepatic delta-ALA-D. In the presence of Hg(2+) or Cd(2+) the inhibitory potency of DMPS increased. Similarly, the inhibitory effects of Hg(2+) and Cd(2+) were markedly increased in the presence of DMSA. In contrast, the inhibitory effect of DMPS was not changed by inclusion of Pb(2+). As observed with DMSA, Zn(2+) did not modified the inhibitory effect of DMPS. Data of the present report support the idea that the complexes formed (metals-DMSA or DMPS) were more inhibitory than the metal (Hg(2+) and Cd(2+)) or the chelating agent alone to the hepatic delta-ALA-D activity, in vitro. The mechanism of hepatic delta-ALA-D inhibition by Hg(2+)-DMPS/DMSA and Cd(2+)-DMPS/DMSA complexes involve the essential thiol groups of the enzyme.

Case report: severe mercuric sulphate poisoning treated with 2,3-dimercaptopropane-1-sulphonate and haemodiafiltration

INTRODUCTION

Inorganic mercury poisoning is uncommon, but when it occurs it can result in severe, life-threatening features and acute renal failure. Previous reports on the use of extracorporeal procedures such as haemodialysis and haemoperfusion have shown no significant removal of mercury. We report here the successful use of the chelating agent 2,3-dimercaptopropane-1-sulphonate (DMPS), together with continuous veno-venous haemodiafiltration (CVVHDF), in a patient with severe inorganic mercury poisoning.

CASE REPORT

A 40-year-old man presented with haematemesis after ingestion of 1 g mercuric sulphate and rapidly deteriorated in the emergency department, requiring intubation and ventilation. His initial blood mercury was 15 580 microg/l. At 4.5 hours after ingestion he was started on DMPS. He rapidly developed acute renal failure and so he was started on CVVHDF for renal support and in an attempt to improve mercury clearance; CVVHDF was continued for 14 days.

METHODS

Regular ultradialysate and pre- and post-filtrate blood samples were taken and in addition all ultradialysate generated was collected to determine its mercury content.

RESULTS

The total amount of mercury in the ultrafiltrate was 127 mg (12.7% of the ingested dose). The sieving coefficient ranged from 0.13 at 30-hours to 0.02 at 210-hours after ingestion. He developed no neurological features and was discharged from hospital on day 50. Five months after discharge from hospital he remained asymptomatic, with normal creatinine clearance.

DISCUSSION

We describe a patient with severe inorganic mercury poisoning in whom full recovery occurred with the early use of the chelating agent DMPS and CVVHDF. There was removal of a significant amount of mercury by CVVHDF.

CONCLUSION

We feel that CVVHDF should be considered in patients with inorganic mercury poisoning, particularly those who develop acute renal failure, together with meticulous supportive care and adequate doses of chelation therapy with DMPS.

Mercuric oxide poisoning treated with whole-bowel irrigation and chelation therapy

Most reported cases of inorganic mercury poisoning are from mercuric chloride. We report a case of mercuric oxide (HgO) powder ingestion. A 31-year-old man presented to an emergency department after ingestion of approximately 40 g of HgO. Soon after ingestion, he developed nausea, vomiting, and abdominal cramping. Abdominal radiograph revealed densely radiopaque material in the stomach. Gastrointestinal decontamination was accomplished with activated charcoal and whole-bowel irrigation with polyethylene glycol solution (Golytely) for 24 hours until repeat abdominal radiographs no longer demonstrated the substance in the gastrointestinal tract. He was also chelated with British anti-Lewisite for 5 days, followed by succimer for 10 days. He had markedly elevated urine and blood mercury levels after ingestion, but except for a mildly depressed serum bicarbonate (19 mEq/L), his chemistry results remained normal including blood urea nitrogen and creatinine. He had an uncomplicated hospital course and remained asymptomatic at 6 months postingestion. Despite elevated urine and blood mercury levels after ingestion of HgO, our patient did not develop the end-organ toxicity typical of inorganic mercury poisoning.

Investigations into the mechanism of 2,3-dimercaptopropanol neurotoxicity

2,3 dimercaptopropanol (BAL), is a dithiol chelating agent, used for the treatment of heavy metal intoxication; however, this compound has low therapeutic efficacy and in some situations may cause neurotoxic effects. In experimental models, administration of high doses of BAL produces seizures that culminate in animal death. However, investigations on the modulation of neurotransmitter system(s) involved in BAL-induced seizures are still lacking in the literature. In the present study, the neurotoxicity of BAL, as measured by the manifestation of seizures was examined and the modulation of glutamatergic and GABAergic receptors and ion channels potentially involved in BAL-induced seizures was investigated. The results demonstrated that BAL (18.6 mg/kg) induced seizures and all mice died within one day. GABAergic allosteric modulators (3 or 12 mg/kg diazepam and 50 mg/kg phenobarbital) blocked the appearance of seizure and reduced almost completely the death caused by BAL. Carbamazepine (5 mg/kg) significantly reduced the incidence of BAL-induced seizures, while sodium valproate and MK-801 were not effective in reducing the incidence of seizures. Valproate (300 mg/kg) and MK-801(0.5 mg/kg) prolonged the latencies for onset of seizures; however, all animals died within one day after BAL administration. High doses of ZnCl2 (135 mg/kg) blocked the appearance of seizures episodes, but no animal survived more than one day. The content of total non-protein -SH in brain of mice treated with 18.6 and 124 mg/kg BAL increased from 0.9+/-0.3 nmol/g (control animals) to 1.7+/-0.3 and 3.5+/-0.8 nmol/g, respectively. In vitro, 0.1-1 mM concentrations of BAL inhibited [3H]glutamate and [3H]MK-801 binding, but increased the binding of [3H]muscimol to brain synaptic plasma membrane. The results reported here demonstrate that GABAergic allosteric modulators (diazepam and phenobarbital) and carbamazepine, a compound that acts by prolonging the recovery of voltage-activated ion channels from inactivation, are able to abolish BAL-induced seizures, while the NMDA antagonist (MK-801) prolonged the latencies for onset of seizures suggesting that modulators of this subtype of glutamate receptor have a modest role on BAL-induced seizures. The results of the present study suggest that allosteric modulators of GABAergic system and carbamazepine, a voltage-gated Na+-channel antagonist, should be considered for the treatment of animals or patients intoxicated with BAL.

Treatment of mercury intoxication

The element mercury exists as inorganic, elemental, or organic species. Routes of exposure and toxicity in humans vary according to the species of mercury involved. Treatment of mercury poisoning generally requires the use of sulfhydryl bond-containing chelation agents, including the parenterally administered dimercaprol and its oral congeners. These oral chelators, meso-2,3-dimercaptosuccinic acid and sodium 2,3-dimercapto-1-propanesulfonate, have numerous advantages over dimercaprol, including less toxicity. Although dimercaprol is contraindicated in organic mercury exposures, meso-2,3-dimercaptosuccinic acid and sodium 2,3-dimercapto-1-propanesulfonate may be used to chelate all species of mercury. Recent evidence suggests that their efficacy in organic mercury poisoning is uncertain.

Myocardial elements content and cardiac function after repeated i.v. administration of DMPS in rabbits

1. A dithiol chelating agent--2,3-dimercapto-1-propanesulphonate (DMPS)--may be administered in acute or chronic intoxication with certain heavy metals (e.g. cadmium, cobalt, lead) that may cause cardiotoxicity. 2. DMPS can act as a depleter of physiologically important elements (e.g. potassium, magnesium, calcium) in various tissues including cardiac one. The possibility of subsequent alteration in cardiac function cannot be excluded. 3. Changes in the myocardial concentration of the above mentioned elements at the end of the experiment and cardiac function were studied during repeated i.v. administration of DMPS as single doses of 50 mg/kg/ week for 10 weeks in rabbits. Biochemical, haematological and histological examinations were also performed. 4. Most of the measured parameters were not affected by the repeated administration of DMPS. A significant decrease in magnesium and a near significant decrease in calcium in cardiac muscle was not accompanied by functional or morphological changes. It is still suggested, however, that care should be taken in using DMPS for treating patients with cardiotoxicity as a result of poisoning with heavy metals.

Utilization of renal slices to evaluate the efficacy of chelating agents for removing mercury from the kidney

Mercury is an environmental contaminant that preferentially accumulates in the kidney. It has been previously shown using proton-induced X-ray emission analysis that mercury (HgCl2) accumulated in precision-cut rabbit renal cortical slices. In this study, the efficacy of seven chelating agents for the removal of Hg from renal slices has been examined. Rabbits were injected with HgCl2 (10 mg/kg) and 3 h later kidneys were sliced, or renal slices were exposed in vitro to a mildly toxic concentration of HgCl2 (5 x 10(-5)M, 4 h). The slices were then treated in vitro with 10 mM concentrations of EDTA, lipoic acid (LA), penicillamine (PA), glutathione (GSH), 1,4-dithiothreitol (DTT), DMSA, or DMPS. DMPS proved to be the most effective in mobilizing Hg from in vivo or in vitro HgCl2-exposed renal tissue ( > 85% of control after 3 h incubation). Relative efficacies for the seven agents were DMPS > DMSA, PA > DTT, GSH > LA, EDTA. The use of renal slices appears to be a useful in vitro tool for assessing the efficacy of chelating agents on mobilizing accumulated Hg from renal tissue.