Toxins, Stings and Anaphylaxis in the Field

In depth

The one-page summary above is what the PDF prints. These sections go further.

The poisoned patient: approach and destination

• NASEMSO universal poisoning care: make the scene safe (a CO detector on the first-in bag), use PPE, check vital signs including temperature, attach the monitor and consider a 12-lead, check glucose, and follow SpO₂ and ETCO₂ because breathing can fail over time. Watch rate, rhythm, QRS and QT on the monitor.
• History that changes care: the exact product, immediate or sustained release, time, route, amount, alcohol or other drugs. Bring all medications from the scene if it is safe, and consider the threat the agent poses to the crew and the hospital.
• Treatment: a patent airway, oxygen to 94-98% and ventilation for hypoventilation, IV access, 20 mL/kg for hypoperfusion, and the specific antidote from the agent guideline (doses on toxicology-antidotes).
• Oral agents: NASEMSO advises against any oral agent, charcoal included, when mental status may fall quickly, and for petroleum products. Ipecac is no longer recommended. Flumazenil is not indicated in suspected benzodiazepine overdose because it can cause intractable seizures.
• Engage the regional poison center early (1-800-222-1222): it guides therapy and tracks outcomes.
• Capacity: NASEMSO states that a person who has attempted suicide, voiced suicidal intent or raises that suspicion cannot be regarded as having decision-making capacity and may not decline transport. This decides the rat-bait and intentional-overdose calls.
• Destination matters for some poisons: a hemodialysis center for severe metformin poisoning (EXTRIP), a hospital that stocks antivenom for black widow, bark scorpion and pit viper bites (NASEMSO), and pediatric capability for a sick child.

Opioids, buprenorphine and sedatives

• Naloxone (NASEMSO): support airway and breathing first, then titrate naloxone to adequate breathing, not to full waking. Adult 0.4-2 mg IV or IM, up to 4 mg IN; child 0.1 mg/kg (max 2 mg IV/IM, 4 mg IN). The reversal may end within an hour while many opioids last 4 hours or longer, so monitor for re-sedation. High-potency opioids may need larger or repeated doses. Naloxone does not help in cardiac arrest.
• Fentanyl patches: NASEMSO says remove any opioid patch found on an overdose patient. The fentanyl transdermal label carries a boxed warning that heating pads, electric blankets, heat lamps, hot baths and saunas raise absorption and have caused fatal overdose; a fever of 40 °C could raise serum levels by about a third. After removal, skin depots keep releasing drug: levels fall about 50% in 20-27 hours, and the label asks for monitoring for at least 72-96 hours after an overdose.
• Incidental exposure of responders: NASEMSO notes that opioids have minimal vapor pressure and are not an exposure risk unless aerosolized or ingested. The ACMT/AACT statement (PMC; the verifier could not reopen it, so this is the writer's reading) says responders have not been confirmed poisoned by incidental contact, that small skin exposures are very unlikely to cause toxicity, and that naloxone is for objective hypoventilation or a depressed level of consciousness, not dizziness or anxiety. Wash skin with soap and water. A tingling, anxious, tachypneic officer with a low ETCO₂ and reactive pupils is hyperventilating.
• Field buprenorphine: the 2026 NAEMSP statement recommends that EMS scope allow buprenorphine and that systems build low-barrier protocols linked to treatment. In the first 131 San Francisco cases, 62.6% were in withdrawal after naloxone, the median COWS score was 15, and 94.9% of those with scores improved, with no prehospital adverse effects recorded; the one exclusion crews missed without physician help was recent methadone use. Classic pharmacology teaching (not from an opened source): buprenorphine is a high-affinity partial agonist, so it can precipitate withdrawal in a patient maintained on a full agonist, and methadone toxicity can return as naloxone wears off. NASEMSO also notes methadone can prolong the QT.
• GHB: Merck describes brief euphoria then coma in overdose, apnea when it is combined with alcohol or other sedatives, and complete recovery in most patients within 6-8 hours; flumazenil has no role, and a single naloxone dose only excludes an opioid. In a Swiss emergency department series of 78 cases, coma was the commonest reason for admission, the median time to regain consciousness was 90 minutes, and recovery was sudden in 32%. Support ventilation with bag-mask and capnography, position for vomiting, and be ready for a combative awakening.
• Gabapentin: the label says it is excreted unchanged by the kidneys, its half-life rises from 5-7 hours to about 52 hours when creatinine clearance is below 30 mL/min, and doses must be cut in renal impairment. Overdose brings double vision, tremor, slurred speech, drowsiness and lethargy, with fatal respiratory depression reported, especially with opioids or other depressants. It can be removed by hemodialysis, so tell the ED about the kidney disease.

Cardiotoxic, delayed and interacting drugs

• Loperamide: an opioid that acts on the gut and stays out of the brain at label doses; people self-treating withdrawal take far larger amounts to reach central effects (Akel 2018 abstract). Overdose is linked to QT prolongation, ventricular tachycardia and sudden death; classic teaching, not confirmed in the abstract and keywords opened, adds sodium-channel (wide QRS) and hERG block. NASEMSO: magnesium 1-2 g IV over 10 minutes for torsades; ondansetron is contraindicated with a prolonged QT.
• Bupropion: StatPearls lists seizures, tachycardia and agitation as common in overdose, with status epilepticus, arrhythmias and cardiogenic shock in severe cases; extended-release forms can cause seizures up to 24 hours after ingestion, so patients need prolonged observation. Benzodiazepines treat the seizures.
• Isoniazid: the label says overdose signs appear in 30 minutes to 3 hours, with intractable seizures, coma and severe metabolic acidosis. Pyridoxine is given IV gram for gram with the isoniazid dose, or 5 g in an adult when the amount is unknown (the label says over 30-60 minutes in an asymptomatic patient and as an initial bolus in a symptomatic one), repeated if seizures continue. EMS rarely carries that much pyridoxine, so early notification and the pill bottle let the hospital have it ready.
• Metformin: in large overdose, classic teaching (not from the abstract opened) is a lactic acidosis with deep, rapid breathing, a low ETCO₂ and a normal glucose. EXTRIP recommends extracorporeal treatment for severe poisoning: lactate above 20 mmol/L, pH 7.0 or below, shock, failure of standard measures, or a decreased level of consciousness, with intermittent hemodialysis first. Direct transport to a dialysis-capable center, with medical direction, when the patient can tolerate the trip.
• Valproate: the Depakote label (section 5.9) warns that hyperammonemia can occur despite normal liver tests and should be considered in any patient with unexplained lethargy, vomiting or a change in mental status; ammonia is measured and the drug stopped if it is high.
• Superwarfarins (brodifacoum and others): about 100 times as potent as warfarin with a much longer half-life (brodifacoum 16-36 days). Bleeding (gums, nose, urine, gut) can start days after ingestion. In the Kodali case, vitamin K1 was raised to 100 mg daily and tapered over about 5 months; plasma or factor replacement treats active bleeding. One dose of vitamin K does not end it.
• Timolol eye drops: the label says the timolol is absorbed systemically, is contraindicated in asthma or a history of it, has caused deaths from bronchospasm, and that beta-blocked patients may not respond to usual epinephrine doses in anaphylaxis. NASEMSO bronchospasm care: albuterol 5 mg nebulized, with ipratropium 0.5 mg (up to 3 doses), which works without the beta receptor.
• Disulfiram-alcohol reaction: disulfiram irreversibly blocks aldehyde dehydrogenase, so acetaldehyde builds up: flushing, throbbing headache, vomiting, chest pain and, in severe cases, shock, ST depression or infarction. Enzyme activity takes 6 or more days to recover. Treat with fluids and a vasopressor; because disulfiram also inhibits dopamine beta-hydroxylase, Segher calls dopamine futile, and NASEMSO already prefers norepinephrine (0.05-0.5 mcg/kg/min), keeping dopamine for when norepinephrine or epinephrine is unavailable. Fomepizole is a hospital option for resistant cases.
• Methylene chloride (paint stripper): absorbed through lungs and skin, stored in fat and metabolized to carbon monoxide, so carboxyhemoglobin can keep rising for hours after exposure ends and stay raised for 1-2 days. ATSDR: there is no antidote, and normobaric 100% oxygen is useful for the released CO; do not discharge on a carboxyhemoglobin level alone because it can rebound when oxygen stops; dysrhythmias may appear hours after a serious exposure.

Children, caustics and street drugs in detail

• Laundry detergent pods: in Beuhler 2013, three of four children needed intubation; reviewers warn of rapid neurologic decline, airway compromise and caustic injury, possibly from the surfactant. Drooling and hoarseness are airway warnings. NASEMSO caustic care is airway assessment, and its universal care advises against oral agents when mental status may fall.
• Salicylates: Merck notes that under 5 mL of oil of wintergreen is equivalent to about 7,000 mg of aspirin and can kill a young child; acute toxicity typically starts at 150 mg/kg, and absorption is usually nearly complete by 6 hours, so an early normal exam means little. NASEMSO: let a salicylate patient breathe on their own, even fast, until they tire or desaturate, because manual ventilation worsens the acidosis.
• Nicotine: NIOSH describes an early stimulant phase (15 minutes to 1 hour: vomiting, salivation, bronchorrhea, tachycardia, hypertension, tremor) and a late depressive phase (30 minutes to 4 hours: bradycardia, hypotension, seizures, paralysis). Death comes from breathing-muscle paralysis, bronchorrhea and cardiovascular collapse. Care: benzodiazepines for seizures, atropine as the mainstay for cholinergic effects, fluids, then a vasopressor.
• Cannabis: Merck advises considering THC ingestion in any child with altered mental status and no other explanation; in children under 5, doses above 5 mg/kg of THC have caused respiratory depression. Adult acute effects are tachycardia, conjunctival injection and impaired cognition. Edibles often look like candy, so bring the package.
• Caustics (Merck): alkalis cause liquefaction necrosis that keeps spreading and mainly injure the esophagus; acids mostly injure the stomach. Normal lips and mouth do not exclude serious injury. Do not induce emesis, lavage, neutralize or give charcoal. Dilution with water or milk helps only in the first few minutes after a liquid and is avoided with nausea, drooling, stridor or signs of perforation.
• Body stuffers swallow a poorly wrapped bag to hide it (packers swallow well-sealed packets to smuggle). Merck notes stuffers and packers may need decontamination or surgery; Moreira 2011 found no life-threatening effects in 106 cocaine stuffers observed for 6 hours, which supports ED observation, not a field release to jail.
• Mushrooms (Merck): symptoms within about 2 hours usually mean a less dangerous mushroom; symptoms that start after 5 hours are the warning. Amanita phalloides causes 95% of mushroom deaths: severe gastroenteritis at 6-12 hours, sometimes hypoglycemia, a few days of apparent improvement, then liver failure. Treat glucose and fluids and bring leftovers or photos.
• Cannabinoid hyperemesis (Razban 2022): hot showers or baths ease symptoms in 92.3%; IV fluids and electrolytes come first. Ondansetron and metoclopramide help little and opioids can worsen vomiting; haloperidol (0.05-0.1 mg/kg) or droperidol, after an ECG for the QT, and topical capsaicin are the most promising. NASEMSO lists droperidol 1.25 mg IV/IM for adult nausea and contraindicates it with a long QT. Only lasting abstinence cures the syndrome.

Marine toxins in detail

• Ciguatera (CDC Yellow Book 2026): large reef carnivores such as barracuda, grouper, amberjack and moray eel. Symptoms usually start 3-6 hours after the meal (up to 30): diarrhea, vomiting and cramps, then paresthesias, aching or loose-feeling teeth and temperature reversal (cold feels hot), which is characteristic but not always present. Bradycardia, heart block and hypotension can occur; symptomatic bradycardia may need atropine (NASEMSO 1 mg q3-5 min, max 3 mg, then pacing). No antidote; mannitol has only uncontrolled evidence.
• Scombroid (CDC): bacteria in poorly chilled tuna, mackerel, mahi mahi and similar fish turn histidine into histamine. Within 10-60 minutes: flushing of the face and upper body, severe headache, itching, cramps, diarrhea and palpitations, mimicking allergy. Several sick diners is the strongest clue. H1 antihistamines usually work; symptoms resolve within 12 hours, sometimes 48. Treat airway swelling, bronchospasm or shock as anaphylaxis.
• Tetrodotoxin (CDC, DAN): found in pufferfish and the blue-ringed octopus, whose bite is usually painless. Numb lips and tongue, trouble speaking and swallowing, then progressive paralysis reaching the breathing muscles (CDC: ascending), sometimes within minutes. There is no antivenom; care is ventilation (bag-mask, then an advanced airway) and transport, and survivors of the first 24 hours usually recover fully. DAN advises a pressure-immobilization wrap as first aid, but ventilation comes first. Classic teaching, cited by the linked bank item to StatPearls (the verifier could not open it): the paralyzed patient may be fully aware, so talk to them and follow protocol on sedation for an advanced airway.
• Jellyfish (NASEMSO): scrape off remaining tentacles or nematocysts, then immerse in hot water at 45 °C (113 °F); Merck gives 40-43 °C. Vinegar deactivates nematocysts of many species but can fire those of sea nettles and Physalia, so know your local species; Merck also says no vinegar for Portuguese man-of-war.
• Venomous spines (NASEMSO, Merck, Niżnik 2024): immerse a stingray, lionfish or scorpionfish wound in hot water to relieve pain; Merck calls warm water unverified for stingrays and gives no temperature; the Niżnik review found no stingray-specific figure, one review advising 45 °C or less for up to 2 hours or until pain eases, a lionfish series using 35-40 °C for 60 minutes, and thermal burns are reported. Merck adds salt-water irrigation, removing only superficial spines, tetanus prophylaxis, and ED exploration for retained sheath fragments. No tourniquet, tight bandage, incision, suction or ice for any envenomation (NASEMSO).

Bites and stings on land in detail

• Black widow (Merck): painful cramps spread from the bite to large trunk muscles, with a rigid abdomen that can mimic a surgical abdomen, sweating, hypertension, tachycardia and vomiting. Opioids and benzodiazepines are first-line; muscle relaxants and calcium salts work poorly. Antivenom is used for severe envenomation, ideally with a toxicologist. NASEMSO: muscle pain is the hallmark; choose a hospital with antivenom when feasible.
• Tick paralysis (Merck): Dermacentor and Amblyomma ticks in North America secrete a toxin only after several days of feeding, causing incoordination and ascending flaccid paralysis that can reach bulbar and breathing muscles. One tick is enough, often on the back of the skull or near the spine, so search the whole body including the hair. Paralysis usually starts to resolve within hours of removal, though it can progress for 24-48 hours; support breathing as needed.
• Massive bee or wasp attack: the dose of venom, not allergy, causes hemolysis, rhabdomyolysis, kidney and liver injury and coagulopathy. Merck: about 22 stings/kg can be tolerated, an adult can survive more than 1,000 stings, and 500 can kill a child. Castagnoli 2021: in children, more than 1 sting/kg warrants laboratory evaluation and follow-up at 24 hours, and kidney injury can appear days later. Dark urine suggests rhabdomyolysis. NASEMSO: 20 mL/kg up to 2 L, cardiac monitor, transport.
• Large local reactions (Merck): redness and swelling peak at about 48 hours, can last a week and can involve a whole limb; they are often mistaken for cellulitis, which is suggested by redness that starts a day or two later, fever, chills or marked pain. Treat with a wrapped ice pack, oral antihistamine or NSAID; epinephrine is for systemic involvement only.
• Embedded stingers: a honeybee leaves its barbed stinger and venom sac behind. NASEMSO: remove it safely without squeezing the apparatus; Merck: scrape it out quickly with a dull edge. Do not delay removal to find the perfect tool, and never delay epinephrine for it.
• Bats (ACIP 2008): bat bites can be tiny and unnoticed. A deeply sleeping person who wakes to a bat in the room, or a bat found with an unattended child or an intoxicated or impaired adult, needs evaluation for rabies prophylaxis even without a visible wound. Capture the bat safely (not bare-handed) for testing; about 94% of submitted bats are not rabid, and a negative test ends prophylaxis. Involve the health department and urge same-day evaluation. Prophylaxis for an unvaccinated person is wound washing, rabies immune globulin 20 IU/kg on day 0 and vaccine on days 0, 3, 7 and 14 (ACIP 2010 replaced the 2008 five-dose schedule).

Anaphylaxis: criteria, treatment and disposition

• NASEMSO criteria (from NIAID): skin or mucosal signs with respiratory compromise, low blood pressure or end-organ dysfunction; or hypotension after a known allergen for that patient (adult systolic under 90); or two or more of skin, respiratory, persistent gastrointestinal or circulatory signs soon after a likely allergen. Skin signs may be absent in up to 40%, and most fatal food reactions in children had none. Signs in one system only are a non-anaphylactic allergic reaction.
• WAO 2020 condenses this to two criteria; the second is hypotension, bronchospasm or laryngeal involvement after a known or highly probable allergen, even without skin signs. WAO lists removing the trigger (for example stopping a drug being given) beside calling for help and IM epinephrine, and places most patients supine (sitting if breathing is hard, recovery position if unconscious).
• Epinephrine dose: NASEMSO 0.3 mg IM at 25 kg or more and 0.15 mg under 25 kg, anterolateral thigh, repeated every 5-15 minutes; the EpiPen label gives 0.3 mg from 30 kg; WAO and the Canadian guide dose 0.01 mg/kg up to 0.5 mg. Wheeze: albuterol 2.5-5 mg or nebulized epinephrine 1 mg/mL, 5 mL; stridor: nebulized epinephrine. Hypoperfusion: 20 mL/kg isotonic fluid over 15 minutes, repeated.
• Refractory shock: NASEMSO considers an epinephrine drip when collapse persists despite repeated IM doses and at least 60 mL/kg of fluid; its text gives 0.5 mcg/kg/min, while Merck starts at 0.1 mcg/kg/min and titrates by 0.05 every 2-3 minutes. Follow your protocol. For a beta-blocked patient with a poor response, Merck gives glucagon 1-5 mg IV over 5 minutes, then an infusion.
• Adjuncts: diphenhydramine 1 mg/kg (max 50 mg) for hives or itching, with an optional H2 blocker (NASEMSO). WAO calls antihistamines second-line or third-line and steroids controversial; NASEMSO finds no proven benefit of steroids. None of them replaces epinephrine.
• Expired auto-injector: Simons 2000 found that outdated EpiPens deliver less epinephrine the longer they are past expiry, yet advised using one if it is the only device and the solution shows no discoloration or precipitate. The label says to replace a device whose solution is pink, brown, cloudy or has particles.
• Accidental digital injection: the EpiPen label says never inject digits, hands or feet, warns of loss of blood flow and sends the person to the nearest emergency room. In Aljahany 2020, warm water and nitroglycerin gel failed and phentolamine infiltration restored the fingertip. Keep the hand warm; cold and elevation reduce flow. Replace the child's spent device.
• Biphasic reactions and disposition: WAO says about half of biphasic reactions occur in the first 6-12 hours; Merck says they typically recur within 4-6 hours without new exposure. The Canadian guide sends everyone given emergency epinephrine to hospital for observation. A patient who refuses is told this plainly and it is documented.

Angioedema, fainting and other mimics

• Vasovagal faint vs anaphylaxis (Canadian Immunization Guide, Table 1): a faint comes during or within minutes of the injection, with pallor, cold clammy skin, a slow pulse, normal breathing and improvement lying flat or head-down; anaphylaxis starts within minutes to hours, brings hives, swelling, itching or redness, a fast pulse, cough, wheeze or stridor, and does not improve lying flat. In doubt, treat. NASEMSO lists vasovagal events in the anaphylaxis differential.
• ACE-inhibitor angioedema (Merck): bradykinin-mediated, so no hives; under 1% of users but about 30% of ED angioedema; can start soon after the drug or years later; lips, tongue and upper airway most often. Epinephrine, steroids and antihistamines have not been shown to work, swelling may take more than 30 minutes to settle, and intubation is more likely: protect the airway, avoid sedation, transport early and prepare for a difficult airway. The drug is stopped; swelling usually resolves 24-48 hours later.
• Hereditary angioedema (Merck): C1 inhibitor deficiency or dysfunction, bradykinin-mediated, no hives; intestinal edema causes colicky pain and vomiting. Allergy drugs have not been shown to work; C1 inhibitor concentrate, icatibant, ecallantide or plasma are hospital treatments.
• Latex: the Spina Bifida Association calls latex allergy a high-risk condition in spina bifida, with latex in catheters, gloves, bandages and balloons, and asks for latex avoidance and medical-alert identification. When a patient reacts after contact with your gloves or equipment, give epinephrine, then change to nitrile gloves and remove every latex item touching the patient.
• Scombroid looks like a food allergy but is histamine in the fish: several diners ill from the same meal, antihistamines, and no lifelong fish-allergy label.

Exam pearls

• The keyed answer is usually the step that removes the source: take off the patch, stop the infusion, change the gloves, get the stinger out, scrape off the tentacles.
• A patient who "feels fine" can still be in the latent phase: extended-release bupropion, isoniazid, wintergreen, Amanita, swallowed drug bags, methylene chloride.
• Naloxone treats hypoventilation from opioids, not anxiety, GHB, gabapentin or loperamide cardiotoxicity.
• Hives alone get diphenhydramine; hives plus any second system, or hypotension after a known allergen, get IM epinephrine now.
• Allergy drugs have not been shown to work in bradykinin angioedema (ACE inhibitor, hereditary): the airway is the treatment.
• Hot water for marine venoms (spines and most jellyfish); never ice, tourniquets or incision for any envenomation.
• Choose the destination that has the fix: dialysis for metformin, antivenom for black widow, pyridoxine for isoniazid.