Is Chelation Therapy Efficient for the Treatment of Intravenous Metallic Mercury Intoxication?

Abstract

The efficacy of treatment for intravenous elemental mercury intoxication has not been fully studied with regard to clinical outcome, and treatment recommendations vary. We treated a 41-year-old man with a history of drug abuse and depression who attempted suicide using 1 mL (13.53 g) metallic Hg i.v. He was admitted to the hospital 2 months later for dyspnoea and thoracic pain and was diagnosed with pneumonia. Hg deposits were seen in the lungs and extra-pulmonary organs. His blood level (372 μg/L) exceeded the population level of 5 μg/L by more than 70 times. Dimercaptopropane sulphonate sodium (DMPS; 600 mg/day orally) was administered for 14 days. One year later, the patient presented with dyspnoea on exertion, fatigue, depression and impaired sleep. His chest X-ray showed multiple opacities (size up to 2.8 cm), and psychological testing revealed a selective cognitive deficit in the area of visual attentiveness, flexibility, source memory and impairment of the motor speed of the dominant upper extremity. Mercury blood level was 158 μg/L and mercury urine output was 1380 μg/24 hr. DMPS (800 mg/day orally) was administered for 40 days; the patient eliminated up to 18 mg Hg/day. His Hg blood level and Hg urine output belong to the highest among reported cases. In spite of the therapy, the patient's blood Hg, complaints and psychological tests showed no improvement. This case report confirms that DMPS does not effectively remove intravenous deposits of metallic Hg.

Rethinking treatment of mercury poisoning: the roles of selenium, acetylcysteine, and thiol chelators in the treatment of mercury poisoning: a narrative review

“…In all four cases the second, third and fourth unithiol treatments resulted in urine mercury concentrations less than 10% of the first unithiol course [51,[74][75][76]. Additionally, the majority (>75%) of urine mercury excretion occurred in the first 48 h of the first treatment, supporting the animal data that the primary effect of the thiol chelators is reduction of renal stores of mercury [51,74,75,77]. In chronic mercury poisoning or post distribution phase, unithiol and succimer appear to have only limited effect on target organ mercury beyond the kidney [78].…”

“…In six reports [13,51,61,[73][74][75] describing unithiol or succimer therapy in patients with either elemental mercury, mercurous chloride or thiomersal [ethymercury] exposure (18 patients in total with daily urinary mercury concentrations), urine mercury concentrations rose dramatically during the first day but returned to near pre-chelation concentrations over the following consecutive days, despite continued therapy [13,51,61,[73][74][75]. Pfab et al…”

“…Likely because of the noted decrease in urine mercury output with continuous dosing, a number of clinicians have employed repeated "pulse" dosing with chelation free periods [51,[74][75][76]. Four reports describe the use of a repeated "pulse" dosing of unithiol:…”

“…1. chronic mercury vapor exposure treated with 30 mg/kg/day (3000 mg/day) for five days repeated three times over 9 weeks [51] 2. chronic mercury vapor treated with 600 mg/day for 14 days with a 38 days break and then 800 mg/day for 20 days [74], 3. chronic occupational mercurous chloride exposure treated with 400 mg/day for 8 days followed by 5 days free of unithiol, then unithiol 400 mg/ day orally for 7 days, followed by 5 days free of unithiol, then 6 days of unithiol 400 mg/day orally [75], 4. chronic mercury exposure in a 10 month old treated with unithiol 20mg/kg/day IV for 4 days followed by 4 cycles of 20 mg/kg/day unithiol IV for 4 "cycles" of 2 days each [76].…”

“…Additionally, in acute high-concentration mercury vapor cases unithiol or succimer appear to have limited effect on pulmonary injury [60,88]. Similar to cases of mercury vapor poisoning, chelation appears to be inadequate to manage the large multi-gram doses associated with elemental mercury injection [57,74,90].…”