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| Module 3: Toxicology - Section 12: Heavy Metals |
| OHM12.X: Mercury - Part 5 |
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The decision to chelate depends on the clinical presentation, (severity of illness), recency of exposure and the species of mercury to which exposure occurred. Dimercaprol, or BAL, is the treatment of choice in acute elemental or inorganic mercury salt poisoning,by providing sulfhydryl groups to bind to the heavy metal. The regimen is 5 mg/kg by deep i.m. injection initially, followed by 2.5 mg/kg one or two times daily or 10 days. In chronic poisoning BAL is of little value and is not reccomended. D-penicillamine is the treatment of choice in chronic poisoning, and is given in doses of 30 mg/day, 250 to 1000 mg q.i.d. depending on the size of the patient and the duration and intensity of exposure.
EDTA is of little value in either acute or chronic poisoning and is not used. There is a great deal of controversy regarding indications for and efficacy of chelation for organic mercurial poisoning. Use of dimercaprol is contraindicated in acute poisoning with organic mercury compounds because this may enhance passage of mercury across the blood-brain barrier.
Newer oral agents including dimercaptopropionic acid, DMPS, and dimercaptosuccinic acid, DMSA, have a lower side effect profiles and are being increasingly tried in various heavy metals poisonings. DMSA is administered in doses of 10mg/kg 3 times daily for 5 days, then twice daily for another 112 days.
Monitoring of clinical status and blood and urine mercury excretion is used to guide repeat dosing.
In acute poisonings, diuresis should be effected during chelation to protect the kidney from high concentrations of mercury. In extreme cases of poisoning (usually with suicidal or homicidal intent) hemodialysis may be necessary.EXERCISES AND INTERACTIVE EXAMPLES | |
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Exercise 1 Exercise 2 |
Example 1 Example 2 Example 3 |
Postgraduate Diploma in Occupational Health (DOH) - Modules 3: Occupational Medicine & Toxicology (Basic) by Profs Mohamed Jeebhay and Rodney Ehrlich, Health Sciences UCT is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License. Major contributors: Mohamed Jeebhay, Rodney Ehrlich, Jonny Myers, Leslie London, Sophie Kisting, Rajen Naidoo, Saloshni Naidoo. Source available from here. For any updates to the material, or more permissions beyond the scope of this license, please email healthoer@uct.ac.za or visit www.healthedu.uct.ac.za.
Last updated Jan 2007.
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