Arsenic is a classic poison; implicated in the deaths of Tchaikovsky and Napoleon. It has also been used as a therapeutic substance since ancient times. It has been used in traditional Chinese medicines and most recently as a chemotherapeutic agent for the treatment of acute promyelocytic leukaemia. Chronic arsenic poisoning is a major pubic health crisis and an environmental disaster in Bangladesh and West Bengal, due to the contamination of ground water that affects millions of people. These chronic problems are beyond the scope of this course.
Arsenic exists in many forms: arsine gas, elemental arsenic, inorganic oxides and organic arsenic. Acute arsenic poisoning is rare. The elemental form of arsenic is non-toxic but the oxides are extremely toxic (trivalent As2O-3 more so than the pentavalent As2O-5). There is limited data on the toxic dose but the lethal dose of inorganic arsenic is about 1-3 mg/kg. Acute toxicity manifests initially within an hour of ingestion as severe nausea, vomiting, diarrhea and abdominal pain. In severe poisoning this is followed by multi-organ failure with cardiac toxicity (QT prolongation, arrhythmias and cardiac failure/collapse), renal failure and hepatic failure. If survival beyond the initial phase occurs, bone marrow suppression, peripheral neuropathy and skin lesions may develop. Treatment includes effective decontamination and early initiation of chelation therapy. The best supportive care is unlikely to prevent death in patients with severe multi-organ failure, or early cardiac effects characterised by QT prolongation, arrhythmias and cardiovascular collapse. Organic arsenic poisoning can cause severe effects but is less toxic than inorganic arsenic.
A 40-year-old man presents 30 minutes after ingesting a mouthful of arsenic trioxide that his father uses for termite control. He has vomited twice already and has abdominal pain. You are at a regional hospital about 3 hours from a major city.
A 66-year-old man presents 3 weeks after a suicide attempt, which he concealed from his family. He states he ingested about a teaspoon of arsenic dust used to kill termites. He gives a history of a gastrointestinal illness for several days and then he recovered. He now presents with a peripheral neuropathy.