August 03, 2010

Q&A: Treatment of Mercury Poisoning

Mercury exists in elemental, inorganic, and organic forms, all of which may be toxic. The toxic manifestation depends on the form of exposure. Thus the form of mercury exposure determines the clinical manifestations, the treatment and prevention of mercury toxicity. Potential toxicity from ingestion of fish during pregnancy is an issue (see below) and fears regarding the use of thimerosal in vaccines have largely been debunked as baseless.

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Mercury and Your Health article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
Elemental mercury toxicity
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Elemental mercury toxicity

Elemental mercury is a silver-colored liquid ("quicksilver") that is volatile at room temperature and causes pulmonary and neurologic toxicity, as well as nephrotoxicity in severe or prolonged exposures. Elemental mercury is vapor at room temperature, and the major route of absorption is through the lungs. Elemental mercury is poorly absorbed via the gastrointestinal tract or skin. Although a small fraction of the mercury vapor taken into the lung is eliminated via exhalation, most absorbed mercury is eliminated in the feces.

The central nervous system is the major site of deposition for mercury derived from inhalation exposure of vapor.

Fish may be contaminated by environmental pollutants, such as methylmercury. Methylmercury exposure, primarily through ingestion of contaminated fish, can cause severe fetal central nervous system damage, as well as milder intellectual, motor, and psychosocial impairment, if eaten by a pregnant woman. For this reason, the FDA and the Environmental Protection Agency have made recommendations for pregnant women (or women who might become pregnant or who are nursing) on the safe types and manner of consuming fish.

MCQ exam: clinical scenario

A 24 year old following her PhD in chemistry is working in a laboratory when a mercury-containing solvent was accidentally spilled over her desk top. She inhaled the vapour. She started coughing and soon after was severely nauseated .She was urgently admitted to the emergency department complaining of a tight feeling in her chest, and having difficulty with breathing.

Which is the best drug treatment for mercury poisoning?

a) Penicillamine
b) Hydrocortisone
c) Subcutaneous adrenalin
d) Glyceryl trinitrate
e) Cephalosporin

MCQ questions & answers on

MCQ exam: answer

The correct answer is A.
Penicillamine is a thiol-based chelating agents for mercury.

MCQ exam: explanation

The agents available to treat mercury poisoning are thiol-based chelating agents including dimercaprol, penicillamine, unithiol, and succimer. Penicillamine is also indicated for the treatment of copper, arsenic, lead and zinc poisoning, Wilson's disease and cystinuria.

Mercury may still be an occupational hazard for people working in medical care facilities. If mercury vapor is inhaled, as much as 80 percent of the inhaled mercury may be absorbed into the bloodstream. The biological half-life of mercury is 60 days. Thus, the body burden will remain for at least a few months.

Very high exposures to mercury vapor in the air can cause acute poisoning as in this case. An outcome may be pneumonia, which can be fatal.

1). UpToDate: Mercury toxicity. Available online:
2). US Food and Drug Administration: Advice about Eating Fish: For Women Who Are or Might Become Pregnant, Breastfeeding Mothers, and Young Children. Available online:

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