Acute nickel carbonyl poisoning

Nickel

Nickel is an essential element for at least several animal species. These animal studies associate nickel deprivation with depressed growth, reduced reproductive rates, and alterations of serum lipids and glucose. Although there is substantial evidence of an essential status for nickel in animals, a deficiency state in humans has not been clearly defined. Nickel is a silver-white metal with siderophilic properties that facilitate the formation of nickel-iron alloys. In contrast to the soluble nickel salts (chloride, nitrate, sulfate), metallic nickel, nickel sulfides, and nickel oxides are poorly water-soluble. Nickel carbonyl is a volatile liquid at room temperature that decomposes rapidly into carbon monoxide and nickel. Drinking water and food are the main sources of exposure for the general population with the average American diet containing about 300 micrograms Ni/d. Nickel is highly mobile in soil, particularly in acid soils. There is little evidence that nickel compounds accumulate in the food chain. Nickel is not a cumulative toxin in animals or in humans. Almost all cases of acute nickel toxicity result from exposure to nickel carbonyl. The initial effects involve irritation of the respiratory tract and nonspecific symptoms. Patients with severe poisoning develop intense pulmonary and gastrointestinal toxicity. Diffuse interstitial pneumonitis and cerebral edema are the main cause of death. Sodium diethyldithiocarbamate is an investigational drug used to chelate nickel following exposure to nickel carbonyl. Nickel is a common sensitizing agent with a high prevalence of allergic contact dermatitis. Nickel and nickel compounds are well-recognized carcinogens. However, the identity of the nickel compound or compounds, which cause the increased risk of cancer, remains unclear. Currently, there are little epidemiological data to indicate that exposure to metallic nickel increases the risk of cancer, or that exposure to the carcinogenic forms of nickel causes cancer outside the lung and the nasal cavity.

Therapeutic review: do diethyldithiocarbamate and disulfiram have a role in acute nickel carbonyl poisoning?

INTRODUCTION

Sodium diethyldithiocarbamate and disulfiram have been proposed as effective nickel chelators. This paper examines the value of these compounds in the treatment of acute nickel carbonyl poisoning by reviewing published experimental and clinical data.

REVIEW

In 2 studies, parenteral administration of diethyldithiocarbamate 50-100 mg/kg to rats immediately following nickel carbonyl exposure ensured the survival of all animals: Mortality fell from 73% to 8% when diethyldithiocarbamate was administered at 10 minutes in a third study. In the same study, there was no protection when diethyldithiocarbamate was administered at 6 hours, and the mortality was greater, though not significantly different, when diethyldithiocarbamate was administered at 24 hours. In another study in mice, total protection was afforded by diethyldithiocarbamate given at 8 hours but this protection was limited when diethyldithiocarbamate was administered at 24 hours, with diethyldithiocarbamate 100 mg/kg apparently being less protective than diethyldithiocarbamate 50 mg/kg. In 3 studies, oral diethyldithiocarbamate administration was less effective than parenteral administration. There are no adequately controlled clinical studies of the use of diethyldithiocarbamate in acute nickel carbonyl poisoning despite claims that this therapy has been effective in the treatment of several hundred such patients. Disulfiram, a metabolite of diethyldithiocarbamate, offered complete protection against nickel carbonyl-induced toxicity when administered in a dose of 1000 mg/kg to rats immediately following nickel carbonyl exposure. In contrast, disulfiram 500 mg/kg offered no protection and disulfiram 1500 mg/kg appeared to enhance mortality, possibly by increasing brain nickel accumulation.

CONCLUSION

Animal studies demonstrate that diethyldithiocarbamate is an effective antidote in acute nickel carbonyl poisoning when it is administered parenterally soon after exposure. However, as no adequately controlled clinical studies have been performed, further clinical data are required before diethyldithiocarbamate can be recommended routinely in acute nickel carbonyl poisoning. If diethyldithiocarbamate is to be employed, it should be administered parenterally soon after exposure as delay in administration may increase nickel carbonyl toxicity. There are currently insufficient data to recommend disulfiram as an alternative to diethyldithiocarbamate even when diethyldithiocarbamate is not available.