Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: The users of illicit drugs is endangered by both unpredictable concentrations of the drugs and by unexpected adulterants that may be present. Cocaine has been adulterated or admixed with numerous substances, among them local anesthetics, amphetamine, phencyclidine, and strychnine. We report three cases of thallium poisoning following nasal insufflation of a substance that was believed to have been cocaine.

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