Poisoning is contact with a substance that results in toxicity. Symptoms vary, but certain common syndromes may suggest particular classes of poisons. Diagnosis is primarily clinical, but for some poisonings, blood and urine tests can help. Treatment is supportive for most poisonings; specific antidotes are necessary for a few. Prevention includes labeling drug containers clearly and keeping poisons out of the reach of children.

Most poisonings are dose-related. Toxicity may result from exposure to excess amounts of normally nontoxic substances. Some poisonings occur from exposure to substances that are poisonous at all doses. Poisoning is distinguished from hypersensitivity and idiosyncratic reactions, which are unpredictable and not dose-related, and from intolerance, which is a toxic reaction to a usually nontoxic dose of a substance.

Poisoning is commonly due to ingestion but can result from injection, inhalation, or exposure of body surfaces (eg, skin, eye, mucous membrane). Many commonly ingested nonfood substances are generally nontoxic (see Table 1: Poisoning: Substances Usually Not Dangerous When Ingested*); however, almost any substance can be toxic if ingested in excessive amounts.

Table 1
Substances Usually Not Dangerous When Ingested* Adhesives Barium sulfate Bathtub toys (floating) Blackboard chalk (Ca carbonate) Candles (insect-repellent type may be toxic) Carbowax (polyethylene glycol) Carboxymethylcellulose (dehydrating material packed with drugs, film, and other products) Castor oil Cetyl alcohol Contraceptives Crayons (children's; marked A.P., C.P., or C.S. 130–46) Dichloral (herbicide) Dry cell battery (alkaline) Glycerol Glyceryl monostearate Graphite Gums (eg, acacia, agar, ghatti) Ink (amount in one ballpoint pen) Iodide salts Kaolin Lanolin Linoleic acid Linseed oil (not boiled) Lipstick Magnesium silicate (antacid) Matches Methylcellulose Mineral oil (if not aspirated) Modeling clay and other modeling compounds Paraffin, chlorinated Pencil lead (graphite) Pepper, black (except inhaled in mass) Petrolatum jelly Polyethylene glycols Polyethylene glycol stearate Polysorbate Putty Shaving cream Silica (silicon dioxide) Spermaceti Stearic acid Sweeteners Talc (except when inhaled) Tallow Thermometer fluid (including liquid mercury) Titanium oxide Triacetin (glyceryl triacetate) Vitamins, children's multiple with or without iron Vitamins, multiple without iron *This table is intended only as a guide; substances may be combined with phenol, petroleum distillate vehicles, or other toxic chemicals. A poison control center should be consulted for up-to-date information. Almost any substance can be toxic if ingested in sufficient amounts.

Accidental poisoning is common among young children, who are curious and ingest items indiscriminately despite noxious tastes and odors; usually, only a single substance is involved. Poisoning is also common among older children, adolescents, and adults attempting suicide; multiple drugs, including alcohol, acetaminophen, and other OTC drugs, may be involved. Accidental poisoning may occur in the elderly because of confusion, poor eyesight, mental impairment, or multiple prescriptions of the same drug by different physicians.

Occasionally, people are poisoned by someone who intends to kill or disable them (eg, to rape or rob them). Drugs used to disable (eg, scopolamine, benzodiazepines, γ-hydroxybutyrate) tend to have sedative or amnestic properties or both. Rarely, parents, who may have some medical knowledge, poison their children because of unclear psychiatric reasons or a desire to cause illness and thus gain medical attention (a disorder called Munchausen syndrome by proxy—see Somatoform and Factitious Disorders: Munchausen Syndrome by Proxy).

Most poisons are metabolized, pass through the GI tract, or are excreted. Occasionally, tablets (eg, aspirin, iron, enteric-coated drugs) form large concretions (bezoars) in the GI tract, where they tend to remain, continuing to be absorbed and causing toxicity.

Symptoms and Signs

Symptoms and signs vary depending on the substance (see Table 8: Poisoning: Symptoms and Treatment of Specific Poisons ). Also, different patients poisoned with the same substance may present with very different symptoms. However, 6 clusters of symptoms (toxic syndromes, or toxidromes) occur commonly and may suggest particular classes of substances (see Table 2: Poisoning: Common Toxic Syndromes (Toxidromes)). Patients who ingest multiple substances are less likely to have symptoms characteristic of a single substance.

Table 2
Common Toxic Syndromes (Toxidromes) Syndrome Symptoms Common Causes Anticholinergic Tachycardia, hyperthermia, mydriasis, warm and dry skin, urinary retention, ileus, delirium (“mad as a hatter, blind as a bat, red as a beet, hot as a hare, and dry as a bone”*) Antihistamines Atropine Belladonna alkaloids Jimson weed Mushrooms (some) Psychoactive drugs (many) Scopolamine Tricyclic antidepressants Cholinergic, muscarinic SLUDGE syndrome (salivation, lacrimation, urination, defecation, GI cramps, and emesis), miosis, bronchorrhea, wheezing, bradycardia Carbamates Mushrooms (some) Organophosphates Physostigmine Pilocarpine Pyridostigmine Cholinergic, nicotinic Tachycardia, hypertension, fasciculations, abdominal pain, paresis Black widow spider bites Carbamates Insecticides (some) Nicotine Opioid Hypoventilation, hypotension, miosis, sedation, possibly hypothermia Opioids (eg, diphenoxylate, fentanyl, heroin, methadone, morphine, pentazocine, propoxyphene) Sympathomimetic Tachycardia, hypertension, mydriasis, agitation, seizures, diaphoresis, hyperthermia, psychosis (after chronic use) Amphetamines Caffeine Cocaine Ephedrine MDMA (Ecstasy) Phenylpropanolamine Theophylline Withdrawal Tachycardia, hypertension, mydriasis, diaphoresis, agitation, restlessness, seizures, hyperreflexia, piloerection, yawning, abdominal cramps, lacrimation, hallucinations Withdrawal of any of the following: Alcohol Barbiturates Benzodiazepines Opioids Sedatives (some) *From Carroll L: Alice in Wonderland. MDMA = methylenedioxymethamphetamine.

Symptoms typically begin soon after contact but, with certain poisons, are delayed. The delay may occur because a metabolite is toxic rather than the parent substance (eg, methanol, ethylene glycol, hepatotoxins). Ingestion of hepatotoxins (eg, acetaminophen, iron, Amanita phalloides mushrooms) may cause acute hepatic failure that occurs one to a few days later. With metals or hydrocarbon solvents, symptoms typically occur only after chronic exposure to the toxin.

Ingested toxins generally cause systemic symptoms. Caustics and corrosive liquids damage mainly the mucous membranes of the GI tract, causing stomatitis, enteritis, or perforation. Some toxins (eg, alcohol, hydrocarbons) cause characteristic breath odors. Skin contact with toxins can cause various acute cutaneous symptoms (eg, rashes, pain, blistering); chronic exposure may cause dermatitis. Inhaled toxins are likely to cause symptoms of upper airway injury if they are water soluble and symptoms of lower airway (lung parenchyma) injury and noncardiogenic pulmonary edema if they are less water soluble. Eye contact with toxins (solid, liquid, or vapor) may damage the cornea and lens, causing eye pain, redness, and loss of vision.

Some substances (eg, cocaine, phencyclidine, amphetamine) can cause severe agitation, which can result in hyperthermia, acidosis, and rhabdomyolysis.

Diagnosis

The first step of diagnosis is to assess the overall status of the patient. Severe poisoning may require rapid intervention to treat cardiopulmonary collapse.

Poisoning may be known at presentation. It should be suspected if patients have unexplained symptoms, especially altered consciousness. If purposeful self-poisoning occurs in adults, multiple substances should be suspected.

History is often the most valuable tool. Because many patients (eg, preverbal children, suicidal or psychotic adults, patients with altered consciousness) cannot provide reliable information, friends, relatives, and rescue personnel should be questioned. Even seemingly reliable patients may incorrectly report the amount or time of ingestion. When possible, the patient's living quarters should be inspected for clues (eg, partially empty pill containers, evidence of recreational drug use). Pharmacy and medical records may provide useful information. In potential workplace poisonings, coworkers and supervisors should be questioned. All industrial chemicals must have a material safety data sheet (MSDS) readily available at the workplace; the MSDS provides detailed information about toxicity and any specific treatment.

In the US, Europe, and parts of Asia and South America, information about household and industrial chemicals can be obtained from poison control centers. Consultation with the centers is encouraged because ingredients, first-aid measures, and antidotes printed on product containers are occasionally inaccurate or outdated. Also, the container may have been replaced, or the package tampered with. Poison control centers may be able to help identify unknown pills based on their appearance. The centers have ready access to toxicologists. The telephone number of the nearest center is often listed with other emergency numbers in the front of the local telephone book; the number is also available from the telephone operator or, in the US, by dialing 1-800-222-1222.

Physical examination sometimes detects signs suggesting particular types of substances (eg, toxidromes, breath odor, needle tracks suggesting IV drug use, stigmas of chronic alcohol use).

Even if a patient is known to be poisoned, altered consciousness may have other causes (eg, CNS infection, head trauma, hypoglycemia, stroke, hepatic encephalopathy, Wernicke's encephalopathy), which should also be considered. Attempted suicide must always be considered in older children, adolescents, and adults who have ingested a drug. After such patients are stabilized, psychiatric intervention should be considered.

Testing

In most cases, laboratory testing provides limited help. Standard, readily available tests to identify common drugs of abuse (often called, “toxic screens”) are qualitative, not quantitative. These tests may provide false results, and they check for only a limited number of substances. Also, the presence of a drug of abuse does not necessarily indicate that the drug caused the patient's symptoms or signs.

For most substances, blood levels cannot be easily determined or do not help guide treatment. For a few substances (eg, acetaminophen, aspirin, carbon monoxide, digoxin, ethylene glycol, iron, lithium, methanol, phenobarbital, phenytoin, theophylline), blood levels may help guide treatment. Many authorities recommend measuring acetaminophen levels in all patients with mixed ingestions because acetaminophen ingestion is common, is often asymptomatic during the early stages, and can cause serious delayed toxicity that can be prevented by an antidote. For some substances, other blood tests (eg, PT/INR for warfarin overdose, methemoglobin levels for certain substances) may help guide treatment. For patients who have altered consciousness or abnormal vital signs or who have ingested certain substances, tests should include serum electrolytes, BUN, serum creatinine, serum osmolality, plasma glucose, and ABGs. Other tests may be indicated for specific substances.

For certain poisonings (eg, due to iron, lead, arsenic, other metals, or to packets of cocaine or other illicit drugs ingested by so-called body packers), plain abdominal x-rays may show the presence and location of ingested substances. X-rays are also indicated for patients with serious symptoms possibly due to poisoning with an unknown substance.

For poisonings with drugs that have cardiovascular effects or with an unknown substance, ECG and cardiac monitoring are indicated.

If blood levels of a substance or symptoms of toxicity increase after initially decreasing or persist for an unusually long time, a bezoar, a sustained-release preparation, or reexposure (eg, repeated covert exposure to a recreationally used drug) should be suspected.

Treatment

Seriously poisoned patients may require ventilation or treatment of cardiovascular collapse. Those with impaired consciousness may require continuous monitoring or restraints. The discussion of treatment for specific poisonings, below and in Table 3: Poisoning: Common Specific Antidotes, Table 4: Poisoning: Guidelines for Chelation Therapy, and Table 8: Poisoning: Symptoms and Treatment of Specific Poisons , is general and does not include specific complexities and details. Consultation with a poison control center is recommended for any poisonings except the mildest and most routine.

Table 3
Common Specific Antidotes Toxin Antidote Acetaminophen N-Acetylcysteine Anticholinergics Physostigmine* Benzodiazepines Flumazenil* β-Blockers Glucagon Ca channel blockers Ca IV insulin in high doses with IV glucose Carbamates Atropine Protopam Digitalis glycosides (digoxin, digitoxin, oleander, foxglove) Digoxin-specific Fab fragments Ethylene glycol Ethanol Fomepizole Heavy metals Chelating drugs (see Table 4: Poisoning: Guidelines for Chelation Therapy) Iron Deferoxamine Isoniazid Pyridoxine (vitamin B6) Methanol Ethanol Fomepizole Methemoglobin-forming agents (eg, aniline dyes, some local anesthetics, nitrates, nitrites, phenacetin, sulfonamides) Methylene blue Opioids Naloxone Organophosphates Atropine Pralidoxime Tricyclic antidepressants NaHCO3 *Use is controversial. Fab = fractionated antibodies.

Table 4
Guidelines for Chelation Therapy Chelating Drug* Metal Dosage† Dimercaprol, 10% in oil Antimony Arsenic Bismuth Chromates‡ Chromic acid‡ Chromium trioxide‡ Copper salts Gold Mercury Nickel Tungsten Zinc salts 3–4 mg/kg via deep IM injection q 4 h on day 1, 2 mg/kg IM q 4 h on day 2, 3 mg/kg IM q 6 h on day 3, then 3 mg/kg IM q 12 h for 7–10 days until recovery Edetate Ca disodium (Ca disodium edathamil), diluted to ≤ 3% Cadmium Lead Zinc Zinc salts 25–35 mg/kg IV slowly (over 1 h) q 12 h for 5–7 days, followed by 7 days without the drug; then repeated Penicillamine Arsenic Copper salts Gold Lead Mercury‡ Nickel Zinc salts 20–30 mg/kg/day in 3–4 divided doses (usual starting dose is 250 mg qid) to a maximum adult dose of 2 g/day Succimer Arsenic, occupational exposure in adults Bismuth Lead if children have blood lead levels > 45 μg/dL (> 2.15 μmol/L) Lead, occupational exposure in adults Mercury, occupational exposure in adults 10 mg/kg po q 8 h for 5 days, then 10 mg/kg po q 12 h for 14 days *Iron and thallium salts are not chelated effectively by these drugs; each has its own chelating drug (see iron and thallium salts in Table 3: Poisoning: Common Specific Antidotes and Table 8: Poisoning: Symptoms and Treatment of Specific Poisons ). †Dosages depend on type and severity of poisoning. ‡Chelating drug of choice.

Initial stabilization

Treatment of any systemic poisoning begins with airway, breathing, and circulatory stabilization (see Respiratory and Cardiac Arrest: Cardiopulmonary Resuscitation (CPR)).

If patients have apnea or compromised airways (eg, foreign material in the oropharynx, decreased gag reflex), an endotracheal tube should be inserted. If patients have respiratory depression or hypoxia, supplemental O₂ or mechanical ventilation should be provided as needed.

In patients with apnea, IV naloxone (2 mg in adults; 0.1 mg/kg in children) should be tried while airway support is maintained. In opioid addicts, naloxone may precipitate withdrawal, but withdrawal is preferable to apnea. If respiratory depression persists despite use of naloxone, endotracheal intubation and continuous mechanical ventilation are required. If naloxone relieves respiratory depression, patients are monitored; if respiratory depression recurs, patients can be treated with another bolus of IV naloxone or mechanical ventilation. Using continuous naloxone infusion to maintain respiratory drive is controversial.

If patients have altered consciousness, plasma glucose should be measured immediately at bedside, or IV dextrose (50 mL of a 50% solution for adults; 2 to 4 mL/kg of a 25% solution for children) should be given empirically. For adults with suspected thiamin deficiency (eg, alcoholics, malnourished patients), thiamin 100 mg IV is given with or before glucose.

Hypotension is treated with IV fluids. If fluids are ineffective, invasive hemodynamic monitoring may be necessary to guide fluid and vasopressor therapy. The 1st-choice vasopressor for most poison-induced hypotension is norepinephrine 0.5 to 1 mg/min IV infusion, but treatment should not be delayed if another vasopressor is more immediately available.

Topical decontamination

Any body surface (including the eyes) exposed to a toxin is flushed with large amounts of water or saline. Contaminated clothing, including shoes and socks, and jewelry should be removed.

Activated charcoal

Charcoal is usually given, particularly when multiple or unknown substances have been ingested. Use of charcoal adds little risk unless patients are at risk of vomiting and aspiration, but its use may not substantially reduce overall morbidity or mortality. When used, charcoal is given as soon as possible. Activated charcoal adsorbs most toxins because of its molecular configuration and large surface area. Multiple doses of activated charcoal may be effective for substances that undergo enterohepatic recirculation (eg, phenobarbital, theophylline) and for sustained-release preparations. Charcoal may be given at 4- to 6-h intervals for serious poisoning with such substances unless bowel sounds are hypoactive. Charcoal is ineffective for caustics, alcohols, and simple ions (eg, cyanide, iron, other metals, lithium). The recommended dose is 5 to 10 times that of the suspected toxin ingested. However, because the amount of toxin ingested is usually unknown, the usual dose is 1 to 2 g/kg, which is about 10 to 25 g for children < 5 yr and 50 to 100 g for older children and adults. Charcoal is given as a slurry in water or soft drinks. It may be unpalatable and results in vomiting in 30% of patients; administration via a gastric tube should be considered. Activated charcoal should probably be used without sorbitol or other cathartics, which have no clear benefit and can cause dehydration and electrolyte abnormalities.

Gastric emptying

Gastric emptying, which used to be well-accepted and seems intuitively beneficial, is not routinely done. It does not clearly reduce overall morbidity or mortality and has risks. Gastric emptying is considered if it can be done within 1 h of a life-threatening ingestion. However, many poisonings manifest too late, and whether a poisoning is life threatening is not always clear. Thus, gastric emptying is seldom indicated and, if a caustic substance has been ingested, is contraindicated (see Poisoning: Caustic Ingestion).

If gastric emptying is used, gastric lavage is the preferred method. Syrup of ipecac has unpredictable effects, often causes prolonged vomiting, and may not remove substantial amounts of poison from the stomach. Gastric lavage may cause complications such as epistaxis, aspiration, or, rarely, oropharyngeal or esophageal injury.

For gastric lavage, tap water is instilled and withdrawn from the stomach with a tube. The largest tube possible (usually > 36 French for adults or 24 French for children) is used so that tablet fragments can be retrieved. If patients have altered consciousness or a weak gag reflex, endotracheal intubation should be done before lavage to prevent aspiration. Patients are placed in the left lateral decubitus position to prevent aspiration, and the tube is inserted orally. Because lavage sometimes forces substances farther into the GI tract, a 25-g dose of charcoal is instilled through the tube first. Then aliquots (about 3 mL/kg) of tap water are instilled, and the gastric contents are withdrawn by gravity or syringe. Lavage continues until the withdrawn fluids appear free of the substance; usually, 500 to 3000 mL of fluid must be instilled. After lavage, a 2nd 25-g dose of charcoal is instilled.

Whole-bowel irrigation

This procedure flushes the GI tract and theoretically decreases GI transit time for pills and tablets. Irrigation has not been proved to reduce morbidity or mortality. Irrigation is indicated for some serious poisonings due to sustained-release preparations or substances that are not adsorbed by charcoal (eg, heavy metals), for drug packets (eg, latex-coated packets of heroin or cocaine ingested by body packers), or for a suspected bezoar. A commercially prepared solution of polyethylene glycol (which is nonabsorbable) and electrolytes is given at a rate of 1 to 2 L/h for adults or at 25 to 40 mL/kg/h for children until the rectal effluent is clear; this process may require many hours or even days. The solution is usually given via a gastric tube, although some motivated patients can drink these large volumes.

Alkaline diuresis

Alkaline diuresis enhances elimination of weak acids (eg, salicylates, phenobarbital). A solution made by combining 1 L of 5% D/W with 3 50-mEq ampules of NaHCO₃ and 20 to 40 mEq of K can be given at a rate of 250 mL/h in adults and 2 to 3 mL/kg/h in children. Urine pH is kept at > 8.0. Hypernatremia, alkalemia, and fluid overload may occur but are usually not serious. However, alkaline diuresis is contraindicated in patients with renal insufficiency.

Dialysis

Common toxins that may require dialysis or hemoperfusion include ethylene glycol, lithium, methanol, salicylates, and theophylline. These therapies are less useful if the poison is a large or charged (polar) molecule, has a large volume of distribution (ie, if it is stored in fatty tissue), or is extensively bound to tissue protein (as with digoxin, phencyclidine, phenothiazines, or tricyclic antidepressants). The need for dialysis is usually determined by both laboratory values and clinical status. Methods of dialysis include hemodialysis, peritoneal dialysis, and lipid dialysis (which removes lipid-soluble substances from the blood), as well as hemoperfusion (which more rapidly and efficiently clears specific poisons—see Renal Replacement Therapy).

Specific antidotes

For the most commonly used antidotes, see Table 3: Poisoning: Common Specific Antidotes. Chelating drugs are used for poisoning with heavy metals and occasionally with other drugs (see Table 4: Poisoning: Guidelines for Chelation Therapy).

Ongoing supportive measures

Most symptoms (eg, agitation, sedation, coma, cerebral edema, hypertension, arrhythmias, renal failure, hypoglycemia) are treated with the usual supportive measures (see elsewhere in The Manual). Drug-induced hypotension and arrhythmias may not respond to the usual drug treatments. For refractory hypotension, dopamine, epinephrine, other vasopressors, an intra-aortic balloon pump, or even extracorporeal circulatory support may be considered. For refractory arrhythmias, cardiac pacing may be necessary. Often, torsades de pointes can be treated with Mg sulfate 2 to 4 g IV, overdrive pacing, or a titrated isoproterenol infusion. Seizures are first treated with benzodiazepines; phenobarbital or phenytoin can also be used. Severe agitation must be controlled; benzodiazepines in large doses, other potent sedatives (eg, propofol), or, in extreme cases, induction of paralysis and mechanical ventilation may be required. Hyperthermia is treated with physical cooling measures rather than with antipyretics. Organ failure may ultimately require kidney or liver transplantation.

Hospital admission

General indications for hospital admission include altered consciousness, persistently abnormal vital signs, and predicted delayed toxicity. For example, admission is considered if patients have ingested sustained-release preparations, particularly of drugs with potentially serious effects, such as cardiovascular drugs. If there are no other reasons for admission and if symptoms are gone after patients have been observed for 4 to 6 h, most patients can be discharged; however, if ingestion was intentional, patients require a psychiatric evaluation.

Prevention

In the US, widespread use of child-resistant containers with safety caps has greatly reduced the number of poisoning deaths in children < 5 yr. Limiting the amount of OTC analgesics in a single container reduces the severity of poisonings, particularly with acetaminophen, aspirin, or ibuprofen. Preventive measures also include clearly labeling household products and prescription drugs, storing drugs and toxic substances in cabinets that are locked and inaccessible to children, promptly flushing expired drugs down the toilet, and using carbon monoxide detectors. Public education measures to encourage storage of substances in their original containers (eg, not placing insecticide in drink bottles) are important. Use of imprint identifications on solid drugs helps prevent confusion and errors by patients, pharmacists, and health care practitioners.

Last full review/revision November 2005