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INTRODUCTION

Poisoning refers to the development of dose-related harmful effects following exposure to chemicals, drugs, or other xenobiotics. Overdosage is exposure to excessive amounts of a substance normally intended for consumption (a pharmaceutical) or an illicit drug. Chemical exposures result in an estimated 5 million requests in the United States for medical advice or treatment each year, and about 5% of victims require hospitalization. Overall mortality is low (<1% of exposures); suicide attempts account for most serious or fatal poisonings (1–2% mortality). Up to 30% of psychiatric admissions are prompted by attempted suicide via overdosage.

Carbon monoxide is the leading cause of death from poisoning. Acetaminophen toxicity is the most common pharmaceutical agent causing fatalities. Other drug-related fatalities are commonly due to analgesics, antidepressants, sedative-hypnotics, neuroleptics, stimulants and street drugs, cardiovascular drugs, anticonvulsants, antihistamines, and asthma therapies. Nonpharmaceutical agents implicated in fatal poisoning include alcohols and glycols, gases and fumes, cleaning substances, pesticides, and automotive products. The diagnosis of poisoning or drug overdose must be considered in any pt who presents with coma, seizure, or acute renal, hepatic, or bone marrow failure.

DIAGNOSIS

The correct diagnosis can usually be reached by history, physical exam, and routine and toxicologic laboratory evaluation. All available sources should be used to determine the exact nature of the ingestion or exposure. The history should include the time, route, duration, and circumstances (location, surrounding events, and intent) of exposure; name of chemical(s) involved, time of onset, nature, and severity of symptoms; relevant past medical and psychiatric history. The Physicians Desk Reference, regional poison control centers, and local/hospital pharmacies may be useful for identification of ingredients and potential effects of toxins.

The diagnosis of poisoning in cases of unknown etiology primarily relies on pattern recognition. The first step is a physical exam with initial focus on the pulse, blood pressure, respiratory rate, temperature, and neurologic status and then characterization of the overall physiologic state as stimulated, depressed, discordant, or normal (Table 32-1).

TABLE 32-1DIFFERENTIAL DIAGNOSIS OF POISONING BASED ON PHYSIOLOGIC STATE

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