Antidotes & Reversal Agents — The Critical Vector

The Big Picture

An antidote reverses a mechanism, not a patient. Giving it doesn't end the job — most require ongoing monitoring for recurrence, rebound, or a second wave of toxicity as the antidote clears faster than the original drug.

Three questions before reaching for any antidote:

1. Is this reversal actually indicated, or is supportive care enough?

2. Does reversing this drug create a new problem — resedation, seizure, rebound toxicity, loss of a needed therapeutic effect?

3. How long does the antidote work compared to the drug it's reversing?

That third question is the one most often skipped, and it's the one that causes the bounce-back call at 3am.

Anaphylaxis & Refractory Shock

Epinephrine: anaphylaxis. The reversal agent this guide had somehow gone this long without.

0.3–0.5 mg IM (1 mg/mL concentration), anterolateral thigh, repeated every 5–15 minutes as needed. Start an IV infusion for refractory anaphylaxis or hemodynamic instability rather than stacking repeated IM doses indefinitely.

IM, not subcutaneous — subcutaneous absorption is slower and less reliable, and the old teaching to prefer it is outdated. Don't let antihistamines or steroids delay epinephrine; they treat the itching and the late-phase response, not the airway or the blood pressure.

Pediatric: 0.01 mg/kg IM (1 mg/mL concentration), same max single dose range as adults (typically capped around 0.3–0.5 mg). Auto-injector tiers per the AAP 2017 clinical report: 0.15 mg for about 10–25 kg, 0.3 mg from about 25 kg (earlier than the 30 kg label cutoff). A 0.1 mg auto-injector (Auvi-Q) is approved for 7.5–15 kg, and 1 mg intranasal epinephrine (neffy) for children 15–30 kg. Below 7.5 kg there is no device dose; draw up 0.01 mg/kg by hand.

Sedation & Opioid Reversal

Naloxone: reverses opioid respiratory depression.

0.04–0.4 mg IV, titrate to breathing, not full waking. Short half-life — watch for re-narcotization as the opioid outlasts the antidote; a naloxone infusion may be needed for long-acting opioids.

In an opioid-dependent patient, full reversal is itself the adverse event — precipitated withdrawal (vomiting, agitation, hypertension, occasionally violent combativeness) can be worse for the patient and the room than the hypoventilation you were treating. Titrate to adequate respiratory rate, not to a fully awake, fully oriented patient.

Pediatric: 0.1 mg/kg per dose for infants and children up to 5 years or 20 kg (higher than the adult-derived 0.01 mg/kg, adopted because it more reliably reverses opioid effect in small children); use adult-range dosing (up to 2 mg) above that age/weight. Doses as high as 0.4 mg/kg have been given to newborns without apparent harm, so the higher pediatric dose is not considered to carry excess risk.

Flumazenil: reverses benzodiazepine sedation.

0.2 mg IV, repeat to a max of about 1 mg.

Pediatric: 0.01 mg/kg IV (max 0.2 mg per dose) over 15 seconds; if inadequate after 45 seconds, repeat 0.01 mg/kg (max 0.2 mg) at 1-minute intervals to a maximum cumulative dose of 1 mg. Pediatric evidence is even sparser than the adult literature — this is built almost entirely from case reports, and the same tricyclic/proconvulsant contraindications apply with, if anything, less margin for error.

Avoid in chronic benzodiazepine use, seizure history, or mixed/unknown overdose. Flumazenil antagonizes the anticonvulsant effect of the benzodiazepine itself, unmasking seizures from co-ingested proconvulsants (classically tricyclics). A meta-analysis of RCTs and a 43-patient case series of flumazenil-induced seizures found tricyclic co-ingestion in 42% of cases, with fatalities among them. Chronic benzodiazepine use alone was not independently associated with seizures in at least one large poison-center series — but risk stratification before giving it is still the standard of care, since ingestant history is often unreliable at presentation.

Neither of these should be reached for reflexively in an undifferentiated overdose — naloxone is low-risk and reasonable to trial; flumazenil is not.

Muscle Relaxant Reversal

Sugammadex: reverses rocuronium/vecuronium (aminosteroid blockers) only — does NOT reverse atracurium or cisatracurium.

2 mg/kg moderate block · 4 mg/kg deep block · 16 mg/kg for immediate reversal after rocuronium-facilitated intubation.

Pediatric: same mg/kg dosing as adults (2–4 mg/kg); approved and studied down to age 2, with trials extending coverage to birth–<2 years showing comparable drug exposure to older children and adults at the same weight-based doses. A case report describes a temporary paradoxical decrease in twitch response after an initial small dose in a pediatric patient — resolved with an additional weight-based dose, a reminder to keep monitoring after redosing rather than assuming full reversal is linear.

Neostigmine + glycopyrrolate: reverses non-depolarizing blockers via acetylcholinesterase inhibition.

Neostigmine 50 mcg/kg (max 5 mg) + glycopyrrolate 10 mcg/kg. Only works once spontaneous recovery has reached T2 — useless in deep block.

Pediatric: same mg/kg dosing as adults; the same T2-recovery requirement and deep-block limitation apply, and are arguably easier to violate in small children where quantitative TOF monitoring is less consistently used.

Evidence	Finding
17-RCT meta-analysis (1,553 patients)	Sugammadex reduced all signs of residual postoperative paralysis, RR 0.46 (0.29–0.71), plus fewer minor respiratory events.
Deep-block reversal comparison	Sugammadex predictably restored TOF ratio ≥0.9 within 5 minutes in 98% of patients vs 11% with neostigmine.
Rocuronium moderate-block RCT	Rescue reversal needed in 4.8% of sugammadex patients vs 60.6% of neostigmine patients (p<0.001).

Neostigmine given for deep or unmonitored block is the classic setup for incomplete reversal — check TOF before choosing which agent, not after extubation.

Poison-Induced Cardiogenic Shock

Beta-blocker, calcium channel blocker, and sodium-channel blocker (TCA and related) overdoses converge on the same clinical picture — bradycardia, hypotension, a dying myocardium — and share an escalating antidote ladder rather than one single fix.

Sodium bicarbonate: QRS widening from sodium-channel blockade — classically TCAs, also citalopram, cocaine, flecainide, diphenhydramine, and hydroxychloroquine.

1 mEq/kg IV bolus (range 0.5–3 mEq/kg), then infusion titrated to a target pH of 7.50–7.55. Treat the QRS, not the acidosis — give it for QRS widening even without acidemia, and stop chasing it once the QRS narrows.

Evidence is uncertain for bupropion, propranolol, and taxine-containing plant poisonings — bupropion's QRS widening comes from gap-junction inhibition, not sodium-channel blockade, so bicarbonate often doesn't help. Give it anyway if the ingestant is unclear, since history is often unreliable and other sodium-channel blockers may be on board.

Pediatric: 1 mEq/kg IV, same pH target (7.50–7.55). In neonates and children under 2, use the dilute 4.2% solution (0.5 mEq/mL) rather than the 8.4% hypertonic solution to reduce the osmotic/sodium load — the target dose is the same, just delivered less concentrated.

Calcium (gluconate or chloride): CCB toxicity, hyperkalemia, magnesium toxicity.

Chloride carries roughly 3x the elemental calcium of an equal volume of gluconate, but is more caustic peripherally — give centrally when possible.

Pediatric: calcium gluconate 60–100 mg/kg/dose IV or IO, may repeat in 10 minutes if needed. Prefer gluconate over chloride in children given the greater peripheral tissue injury risk with chloride in smaller veins.

For hyperkalemia specifically, calcium stabilizes the cardiac membrane but doesn't shift potassium — nebulized or IV albuterol is a useful adjunct that does, alongside insulin/dextrose, working through a different receptor pathway entirely.

Glucagon: beta-blocker overdose (± CCB co-ingestion).

50 mcg/kg IV (typically 3–5 mg) over 1–2 minutes, repeated up to about 10 mg total; then an infusion at the dose that produced a response, per hour (commonly 2–5 mg/h). Expect vomiting; protect the airway. Bypasses the blocked beta-receptor entirely by driving cAMP through a separate G-protein pathway — works even with the receptor fully occupied. Often under-dosed and under-lasting; don't expect it to carry a severe overdose alone.

Pediatric: 0.05–0.15 mg/kg IV over 1–2 minutes (not exceeding 1 mg/min), may repeat once if inadequate response at 10 minutes. Reconstituted glucagon is a 1 mg/mL solution regardless of age — don't confuse dose (mg/kg) with concentration when drawing it up for a small child.

Same mechanism, different patient: glucagon is also the specific rescue for anaphylaxis that isn't responding to epinephrine (section 2) in a patient on chronic beta-blocker therapy, since the beta-blockade can blunt epinephrine's effect the same way it does here.

High-dose insulin/euglycemia (HIE) therapy: refractory beta-blocker or CCB shock, when atropine, calcium, glucagon, and vasopressors aren't enough.

Regular insulin bolus ~1 unit/kg, then infusion 0.5–1 unit/kg/h, titrated up as needed (some refractory cases have used far higher rates). Requires a concentrated dextrose infusion (≥20%) run alongside to maintain euglycemia, and frequent glucose/potassium checks.

Pediatric: same weight-based bolus/infusion approach used in adults, supported mainly by case reports rather than large pediatric series. Central access and a reliable concentrated-dextrose infusion matter even more in small children, who have less glycogen reserve and tip into hypoglycemia faster and harder.

Evidence	Finding
HIE guideline implementation study	More aggressive initial insulin dosing (~1 unit/kg/h) after a formal guideline reduced hypoglycemia (29% vs 80%) compared to the pre-guideline lower-dose approach.
HIE mechanism	Positive inotropy with vasodilation, enhanced myocardial carbohydrate uptake, and improved lactate clearance — mechanisms distinct from and additive to glucagon and calcium.

HIE is increasingly first-line for poison-induced cardiogenic shock at most toxicology-experienced centers, not a last resort — the old sequence of "glucagon, then calcium, then maybe insulin" undersells how early HIE should start once the patient is sick. Watch for delayed hypoglycemia after the infusion is weaned; it can persist for hours.

Toxidrome Rescue Agents

Serotonin syndrome and neuroleptic malignant syndrome look alike at a glance — altered mental status, autonomic instability, hyperthermia — and are told apart by tempo and tone. Serotonin syndrome develops over hours with hyperreflexia, clonus, and tremor (neuromuscular hyperactivity); NMS develops over days with rigidity and sluggish reflexes (neuromuscular hypoactivity). Each has its own rescue agent.

Cyproheptadine: serotonin syndrome not controlled by stopping the drug, benzos, and supportive care alone.

12 mg oral/NG load, then 2 mg every 2 hours until response, up to roughly 32 mg/day. Tablet-only — crush for NG/OG administration.

Pediatric: 0.25 mg/kg/day divided into doses, age-tiered in practice (roughly up to 8 mg/day for ages 2–6, up to 16 mg/day for ages 7–14). Pediatric cyproheptadine overdose itself produces anticholinergic toxicity (dry, flushed, tachycardic, delirious) — worth remembering this drug can cause the very toxidrome-adjacent picture you might be treating it for, at excessive doses.

Evidence is inconclusive; multiple reviews call it widely used but not definitively proven. Give it in moderate-to-severe cases as an adjunct, not a substitute for discontinuing the serotonergic agent(s) and benzodiazepine sedation.

Bromocriptine: neuroleptic malignant syndrome, typically alongside dantrolene in moderate-to-severe cases.

2.5 mg via NG tube or orally every 6–8 hours, uptitrated per response. Oral/enteral only — no IV formulation.

Pediatric: genuinely limited data — NMS itself is rare in children, and bromocriptine dosing here is extrapolated from adult case reports rather than established in pediatric-specific series. Treat this as a last-resort adjunct with even more caution than in adults, and lean on a toxicologist or pediatric critical care consult.

Evidence	Finding
Case-controlled analysis, NMS mortality	Untreated/supportive-only NMS carried a 21% death rate; dantrolene alone reduced it to 8.6%, bromocriptine alone to 7.8%.
271-case review	Combination therapy (dantrolene + bromocriptine) trended toward lower mortality and faster complete remission than either agent alone.

Evidence for both agents is limited to case series and retrospective analyses — no RCT exists for either toxidrome, for the obvious reason that withholding treatment in a severe case would be difficult to justify. Bromocriptine promotes a prothrombotic state (consider VTE prophylaxis) and suppresses lactation; both are oral/enteral-route drugs, a meaningful limitation in an obtunded or intubated patient.

Benztropine or diphenhydramine: acute dystonic reaction from antipsychotics or antiemetics (metoclopramide, prochlorperazine, haloperidol) — a distinct, much more common entity than NMS, and one that resolves in minutes rather than days.

Benztropine 1–2 mg IV/IM, or diphenhydramine 25–50 mg IV/IM.

Pediatric: diphenhydramine 1 mg/kg IV/IM (max 50 mg) is the usual first choice in young children. Benztropine is generally avoided under age 3 and used cautiously in older children given anticholinergic sensitivity at this age — diphenhydramine's wider familiarity and dosing evidence make it the more practical default in pediatrics.

Both work by restoring the dopamine-acetylcholine balance disrupted by dopamine-receptor blockade — this is the fast, satisfying antidote in a shift full of slower ones. Don't confuse a dystonic reaction (bizarre posturing, torticollis, oculogyric crisis, patient fully alert and often frightened) with NMS (days-long onset, fever, rigidity, altered consciousness) — they share a drug class but nothing else about their management.

Anesthesia-Specific Emergencies

Dantrolene: malignant hyperthermia. Stop triggers, 100% O2, active cooling.

2.5 mg/kg IV push, repeated every 5–10 minutes to a suggested ceiling of 10 mg/kg (some patients need 20 mg/kg). Maintenance 1 mg/kg every 4–6 hours for at least 24 hours.

Pediatric: identical mg/kg dosing across all ages — MHAUS makes no age-based distinction for dantrolene dosing, since MH itself is weight-driven pharmacology, not age-driven. Pediatric MH is if anything more common relative to adult cases, so this is not a rare-event calculation to fumble under pressure.

Recrudescence occurs in about 20% of cases, median onset 8.7 hours after the initial event, in 80% by 16 hours — don't stop watching once the first crisis breaks. Call for extra hands early: reconstitution is slow, and know where it's stocked before you need it. Dantrolene is also used off-label in neuroleptic malignant syndrome — see section 6.

Lipid emulsion 20% (Intralipid): local anesthetic systemic toxicity (LAST).

Under 70 kg: 1.5 mL/kg bolus over 2–3 min, then 0.25 mL/kg/min infusion. Over 70 kg: 100 mL bolus over 2–3 min, then 250 mL over 15–20 min. Repeat bolus or double the infusion if unstable. Upper limit ~12 mL/kg.

Pediatric: same weight-based bolus/infusion as adults (1.5 mL/kg, then 0.25 mL/kg/min) — pediatric-specific outcome data is limited, but the dosing itself doesn't change, since it's already calculated per kilogram rather than as a fixed adult quantity.

Per the 2020 ASRA checklist: benzodiazepines are first-line for LAST seizures, not propofol (myocardial depressant on top of an already-toxic heart). For arrest, reduce epinephrine to under 1 mcg/kg boluses and avoid vasopressin, calcium channel blockers, beta-blockers, or other local anesthetics. Off-label, the same lipid-sink mechanism has rescued severe overdoses of other lipophilic drugs (bupropion, some calcium channel blockers) when standard therapy has failed — extrapolated evidence, not a primary indication, but worth knowing when nothing else is working.

Anticoagulant Reversal

See the Bleeding & Reversal Agents guide, Part I. That guide covers protamine (heparin/LMWH), vitamin K + 4F-PCC (warfarin), idarucizumab (dabigatran), and the current state of factor Xa inhibitor reversal following the December 2025 Andexxa withdrawal — plus TEG/ROTEM interpretation and the bedside reversal algorithm. Not duplicated here to keep both documents accurate as guidance changes.

Antiplatelet-associated bleeding, including the PATCH trial data on why platelet transfusion is the wrong reflex in spontaneous ICH, also lives in that guide's Part II.

Pediatric: not covered in detail in either guide — pediatric anticoagulant reversal (vitamin K, 4F-PCC dosing in children) is genuinely a separate lookup; don't extrapolate the adult fixed-dose regimens in the other guide onto a child without checking pediatric-specific references or pharmacy/toxicology.

Toxicology I: Antidote by Substance

Atropine + pralidoxime: organophosphate/carbamate poisoning.

Atropine in doubling doses until secretions dry — atropinize to clear lungs, not to dilated pupils. Pralidoxime per weight-based protocol, reactivates acetylcholinesterase before it ages.

Pediatric: atropine 0.02–0.05 mg/kg IV, doubled every 5–10 minutes until atropinization, same clinical endpoint as adults. Note this differs from the standard pediatric bradycardia dose, which carries a 0.1 mg minimum to avoid paradoxical bradycardia — that floor doesn't apply here, since cumulative organophosphate dosing is calculated purely by weight and can run to grams over days in severe poisoning. Pralidoxime dosed by weight-based protocol, same principle as adults.

Physostigmine: anticholinergic toxidrome (TCAs, antihistamines, jimsonweed and other anticholinergic plants) — a cholinesterase inhibitor, functionally the mirror image of the atropine/pralidoxime pair above.

0.5–1 mg IV/IM over 5–10 minutes, may repeat.

Pediatric: 0.02 mg/kg slow IV (max 0.5 mg per dose), may repeat every 5–10 minutes to a cautious cumulative maximum. Same cardiac caution as adults applies with less margin — avoid if TCA cardiotoxicity is present or suspected.

Use with caution and avoid if TCA cardiotoxicity (wide QRS) is present or suspected — physostigmine can precipitate seizures or asystole in that setting. Reserve for clear anticholinergic delirium without cardiac conduction abnormality.

N-acetylcysteine (NAC): acetaminophen overdose.

IV or oral per weight-based protocol, guided by the Rumack-Matthew nomogram using a serum level drawn ≥4 hours post-ingestion. Nearly 100% hepatoprotective if started within 8 hours; still beneficial after 24 hours or in established liver failure. Start empirically if ingestion time is unknown or exceeds 8 hours while awaiting labs — don't wait for the nomogram to tell you to hurry.

Pediatric: same weight-based protocol as adults — 140 mg/kg oral loading dose then 70 mg/kg every 4 hours for 17 more doses, or the equivalent 3-bag IV protocol (150 mg/kg, then 50 mg/kg, then 100 mg/kg over the standard time windows). A modified two-stage IV regimen has been studied specifically in children to reduce hyponatremia risk from the fluid volume of the standard adult-derived infusion.

Digoxin-specific Fab (DigiFab): life-threatening digoxin toxicity.

Dosed by ingested amount or steady-state level. FDA-cited thresholds: acute ingestion ≥10 mg (adult), or level ≥10 ng/mL soon after ingestion; chronic toxicity with hemodynamic instability, refractory bradyarrhythmia, or potassium >5.0–5.5 mEq/L.

Pediatric: lower acute-ingestion threshold than adults — roughly ≥4 mg (or ≥0.1 mg/kg) triggers consideration, versus ≥10 mg in adults. Same chronic-toxicity clinical triggers (dysrhythmia, hyperkalemia) apply regardless of age; dose by whichever calculation (ingested amount or level) yields the larger number.

Treat the rhythm and the potassium, not the number on the digoxin level alone — post-Fab levels are unreliable for days, since the assay can't distinguish bound from free drug.

Toxicology II: Chelation & Metabolic Rescue

Deferoxamine: iron toxicity.

Chelates free and loosely bound iron; 100 mg binds roughly 10 mg of iron. Consider at serum iron ≥350 mcg/dL with symptoms, or ≥500 mcg/dL regardless of symptoms.

Pediatric: same weight-based infusion approach as adults — commonly started around 15 mg/kg/hr, adjusted to severity. Iron overdose is disproportionately a pediatric exposure (single-adult-dose iron tablets are a classic toddler ingestion), so this is one antidote where the pediatric case is the norm, not the exception.

Watch for hypotension with the infusion — free iron itself is a potent vasodilator, so a patient already volume-down from GI losses can drop further. Vin-rosé urine supports the diagnosis but its absence doesn't rule out significant iron burden.

Lead chelation ladder — succimer, dimercaprol, calcium disodium EDTA.

Succimer (DMSA), oral: BLL >45 mcg/dL (child) or >80 mcg/dL (adult) without encephalopathy. 10 mg/kg every 8 hours for 5 days, then every 12 hours for 14 more days.

Severe poisoning or encephalopathy (BLL ≥70 mcg/dL): dimercaprol (BAL) IM 3–4 mg/kg every 4 hours, started first — followed 4 hours later by calcium disodium EDTA IV 25 mg/kg/day. The delay matters: giving EDTA before dimercaprol can mobilize lead into the brain rather than out of the body.

Pediatric: this entire ladder is already written pediatric-first — lead poisoning is overwhelmingly a young-child exposure (paint chips, contaminated soil, imported goods), and the mg/kg dosing above applies at all ages including infants. The BLL thresholds themselves are lower for children than adults, reflecting children's greater neurodevelopmental vulnerability at any given blood level.

Dimercaprol is no longer manufactured — its sole US manufacturer closed in early 2023. For severe/encephalopathic lead poisoning, current practice is succimer or calcium disodium EDTA monotherapy while awaiting supply, with immediate poison center or medical toxicology consultation. Both agents have also faced intermittent shortages — confirm current availability before counting on either.

Pyridoxine (vitamin B6): isoniazid-induced seizures refractory to benzodiazepines.

Gram-for-gram with the estimated INH ingestion if known; empiric dosing up to 5 g IV if the amount is unknown.

Pediatric: same gram-for-gram principle when the ingested amount is known; empiric dosing when unknown is typically 70 mg/kg IV, up to the same 5 g adult ceiling.

INH blocks the conversion of pyridoxine to its active cofactor form, starving GABA synthesis — benzodiazepines need GABA receptors to work, so they underperform until pyridoxine restores the substrate. This is the seizure that doesn't respond to your first two doses of benzos for a reason.

Leucovorin (folinic acid): methotrexate toxicity, rescuing normal cells from folate antagonism.

15 mg (or 10 mg/m²) IV/PO every 6 hours, starting as soon as toxicity is recognized; increase the dose if the methotrexate level remains elevated. Escalate to glucarpidase (carboxypeptidase G2) for severe toxicity with renal dysfunction and delayed clearance.

Pediatric: already dosed here in mg/m² body surface area rather than a fixed adult quantity, which is inherently the pediatric-appropriate unit — no separate conversion needed, just calculate BSA and apply the same mg/m² figure.

The longer methotrexate sits in the cell, the more it polyglutamates and the harder it becomes to rescue — dose and timing both matter more than either alone.

L-carnitine: valproate-induced hyperammonemia or hepatotoxicity.

Loading dose followed by a continuing infusion or divided dosing; exact optimal dose and route remain unsettled in the literature, though IV administration is generally preferred over oral given limited (14–18%) oral bioavailability.

Pediatric: similar mg/kg loading approach reported in pediatric valproate-hyperammonemia case series, including children under 16 with valproate-induced encephalopathy — dosing is even less standardized in children than adults, so treat published pediatric figures as a starting point for discussion with pharmacy/toxicology, not a fixed protocol.

Valproate depletes carnitine, which is required for the mitochondrial fatty acid metabolism that keeps ammonia detoxification running — replacing it treats the mechanism, not just the ammonia level.

Octreotide: sulfonylurea overdose, to prevent rebound hypoglycemia.

50–100 mcg SC or IV every 6–12 hours. Suppresses insulin secretion directly, added alongside dextrose rather than replacing it.

Pediatric: roughly 1 mcg/kg SC or IV, typically dosed every 6 hours (total daily range around 1–10 mcg/kg/day) — pediatric sulfonylurea exposure is usually accidental single-tablet ingestion by a toddler, so watch for delayed-onset hypoglycemia over many hours even after an initially reassuring glucose.

Dextrose alone can drive a hyperglycemia-hypoglycemia cycle, since the glucose bolus itself triggers more insulin release from a sulfonylurea-primed pancreas. Octreotide breaks that cycle and cuts the need for repeated dextrose boluses.

Not for exogenous insulin overdose — octreotide only suppresses endogenous insulin secretion from the pancreas, and does nothing to insulin that's already been injected. For an insulin overdose (accidental or intentional), sustained dextrose infusion, sometimes for many hours with depot/long-acting formulations, is the actual mainstay, not octreotide.

Toxicology III: The Rest

Methylene blue: two distinct indications, two different roles.

Methemoglobinemia: 1–2 mg/kg IV over 5 minutes.

Refractory vasoplegic shock (post-cardiopulmonary bypass, septic, or drug-induced, once septic/anaphylactic/adrenal causes are addressed): inhibits the nitric oxide–cGMP pathway to reverse pathologic vasodilation — a distinct rationale from its methemoglobinemia use, generally reserved for shock refractory to standard vasopressors.

Pediatric: same 1–2 mg/kg dosing for methemoglobinemia, may repeat in 1 hour if methemoglobin remains >30%. A pediatric-specific safety signal worth knowing: Heinz body hemolytic anemia has been reported in young infants who received methylene blue at doses as low as 4 mg/kg even without G6PD deficiency — infants appear more vulnerable to this than older children or adults at the same weight-based dose.

Avoid in G6PD deficiency — methylene blue relies on G6PD-dependent NADPH to reduce methemoglobin back to hemoglobin, so it fails and can worsen hemolysis in deficient patients. Also risks precipitating serotonin syndrome in patients on SSRIs or other serotonergic agents, since methylene blue is a potent MAO-A inhibitor.

Oxygen (100% normobaric) ± hyperbaric oxygen (HBOT): carbon monoxide poisoning.

100% oxygen via non-rebreather immediately — this alone cuts the CO half-life from roughly 4–6 hours on room air to about 1 hour. Continue until COHb falls to ~3% and for at least 6 hours regardless. In pregnancy, extend oxygen duration substantially (fetal hemoglobin clears CO more slowly) and treat with HBOT if available regardless of maternal COHb level.

Pediatric: same normobaric-oxygen approach and COHb-based reasoning as adults. Pediatric-sized or multiplace chambers accommodating a parent are far less widely available than adult monoplace chambers, so the practical decision to pursue HBOT in a child often comes down to what's within transport distance — factor that into the risk/benefit discussion rather than treating HBOT as equally accessible across ages.

Evidence	Finding
Weaver et al., NEJM 2002	RCT with sham-dive blinding: cognitive sequelae at 6 weeks in 25% of the HBOT group vs 46% with normobaric oxygen — the trial most often cited in favor of HBOT.
Scheinkestel et al., 1999	Earlier RCT found no benefit to HBOT over high-flow normobaric oxygen, and a subsequent critical appraisal (Juurlink, 2023) argued the overall evidence for routine HBOT remains weaker than commonly believed.

This is a genuinely contested therapy, not a settled one — reasonable toxicologists disagree on how aggressively to pursue HBOT. Most guidelines still favor considering it for loss of consciousness, COHb >25%, pregnancy, or significant neurologic/cardiac findings, ideally within hours of exposure, but don't delay definitive care hunting for a chamber if the patient is otherwise stabilizing on high-flow oxygen alone.

Hydroxocobalamin: cyanide poisoning.

5 g IV. Think of it in enclosed-space smoke inhalation with an unexplained lactic acidosis, not just industrial exposure.

Pediatric: 70 mg/kg IV over 15 minutes, not to exceed the adult 5 g dose. Suitable across the full pediatric range from infants to adolescents; a second dose may be given the same way as in adults if severity and response warrant it.

Sodium thiosulfate was the older third leg of the classic cyanide antidote kit (with amyl/sodium nitrite) and is largely superseded by hydroxocobalamin, which doesn't induce methemoglobinemia — a liability in smoke-inhalation patients who may already have carbon monoxide on board. Thiosulfate can still be given alongside hydroxocobalamin for synergistic effect if available, but is no longer the primary agent. The nitrites are the part of the old kit to actively avoid in smoke-inhalation patients: deliberately inducing methemoglobinemia on top of an already CO-loaded, oxygen-starved patient is the opposite of what you want, which is precisely why hydroxocobalamin replaced the nitrite-based approach for this specific population.

Fomepizole: methanol or ethylene glycol poisoning.

Loading dose then maintenance IV, blocking alcohol dehydrogenase before the toxic metabolites (formic acid, glycolic/oxalic acid) can form.

Pediatric: same protocol at all ages — 15 mg/kg loading dose, then 10 mg/kg every 12 hours for 4 doses, then 15 mg/kg every 12 hours until levels clear (adjust timing/dose around dialysis if used). Toxic alcohol ingestion in young children is typically a small accidental sip rather than a large deliberate ingestion, but the same treatment threshold and dosing math apply regardless of the story behind the exposure.

Evidence	Finding
Adverse drug event cohort	Adverse events occurred in 57% of patients treated with ethanol vs 12% with fomepizole for toxic alcohol poisoning.
Medication error comparison	Harmful medication errors: 19% with ethanol vs 7% with fomepizole.

Ethanol still works and remains an acceptable fallback where fomepizole isn't stocked or is cost-prohibitive, but fomepizole's predictable kinetics are why it has replaced ethanol as first-line almost everywhere it's available.

Envenomation & Biological Toxins

CroFab (Crotalidae Polyvalent Immune Fab): North American pit viper envenomation (rattlesnake, copperhead, cottonmouth).

Initial dosing by severity and species: commonly 4 vials for copperhead, 6–12 for rattlesnake, up to a 12-vial initial maximum — repeat to control per protocol, not a one-and-done dose.

Pediatric: same vial-based dosing as adults, not weight-based — antivenom is dosed to neutralize a given venom load, not scaled to patient size. This means a small child receives the identical vial count as an adult with a comparable bite, which can feel counterintuitive the first time you calculate it.

Evidence	Finding
Integrative review, severe envenomation	77% of reported severe venom effects improved or resolved after FabAV therapy; initial control achieved in 50% of cases overall, significantly more often in cohort studies than in case reports (100% vs 29%).

Recurrent or delayed-onset coagulopathy (defibrination syndrome) is common, mostly in patients who didn't receive recommended maintenance dosing — this isn't a single-dose antidote. Reassess coagulation status for days after apparent initial control, especially before any invasive procedure or discharge.

Latrodectus antivenom: black widow spider envenomation, for severe systemic symptoms (severe muscle rigidity, respiratory compromise, refractory hypertension) not controlled by calcium, benzodiazepines, and opioids.

Typically 1 vial, equine-derived.

Pediatric: same 1-vial dosing regardless of size, same vial-not-weight logic as CroFab above. Children and small adults tend to have more severe systemic symptoms per unit of venom than large adults, which can lower the practical threshold to treat rather than observe.

Latrodectism is painful but rarely fatal, and equine-derived antivenom carries real anaphylaxis and serum sickness risk — most cases are managed with calcium, benzodiazepines, and opioids alone, reserving antivenom for severe or refractory presentations rather than reaching for it reflexively.

Anascorp (Centruroides Immune F(ab')2): scorpion envenomation with clinically significant signs — loss of muscle control, roving/abnormal eye movements, slurred speech, respiratory distress, excessive salivation. Regionally relevant anywhere the Arizona bark scorpion (Centruroides sculpturatus) is endemic.

Initial dose: 3 vials IV over 10 minutes; additional vials 1 at a time at 30–60 minute intervals if symptoms persist.

Pediatric: same 3-vial initial dosing regardless of weight — children make up the majority of scorpion-antivenom recipients in practice (roughly two-thirds under age 10 in reported Arizona ED series) and generally resolve symptoms slightly faster than adults after the same dose.

Evidence	Finding
Arizona ED experience, 5 years	Mean time from antivenom infusion to symptom resolution was 1.42 hours across nearly 1,400 patients; children resolved slightly faster than adults.
Dosing controversy	The FDA label recommends 3 vials initial dosing, but the antivenom's country of origin (Mexico, as Alacramyn) uses a more conservative 1-vial, watchful-waiting approach with comparable reported outcomes at a fraction of the cost (~$3,000–4,000 per vial in the US).

Equine-derived with a low serum sickness rate (~0.5%) and no reported true anaphylaxis in the approval studies — safer than its reputation suggests. Reserve for grade III–IV envenomation (cranial nerve and somatic neuromuscular dysfunction), not mild local reactions, and don't be surprised if a toxicologist or poison center pushes back toward a lower starting dose than the package insert.

Botulinum antitoxin (heptavalent): suspected foodborne, wound, or adult intestinal botulism. BabyBIG (botulism immune globulin) is the pediatric/infant-specific equivalent.

Obtained through the CDC or state health department, not routine hospital stock — start the request the moment botulism is clinically suspected.

Pediatric: infant botulism (the classic honey-exposure or environmental spore ingestion presentation under age 1) uses BabyBIG specifically rather than the heptavalent antitoxin used in older children and adults — a single IV infusion dosed at 50 mg/kg (human-derived rather than equine, starting at 0.5 mL/kg/hr and advancing to 1.0 mL/kg/hr if tolerated), obtained through the California Department of Public Health's Infant Botulism Treatment and Prevention Program regardless of what state the case is in. Don't request the standard heptavalent product for a suspected infant case; the ordering pathway and the product itself are both different, and BabyBIG only halts progression — it doesn't reverse paralysis already present, same principle as the adult antitoxin above.

Antitoxin neutralizes only circulating, unbound toxin — it halts progression but does not reverse paralysis already established at the neuromuscular junction. That's the argument for treating on clinical suspicion rather than waiting for lab confirmation, which can take days.

Quick Reference Card & Primary Sources

Agent	Reverses	Adult dose
Sugammadex	Rocuronium/vecuronium	2–4 mg/kg (16 mg/kg immediate)
Neostigmine + glycopyrrolate	Non-depolarizing NMB, T2+	50 mcg/kg (max 5mg) + 10 mcg/kg
Naloxone	Opioid respiratory depression	0.04–0.4 mg IV, titrate (caution: precipitated withdrawal)
Flumazenil	Benzodiazepine sedation	0.2 mg IV, max ~1 mg
Epinephrine	Anaphylaxis	0.3–0.5 mg IM, q5–15min, infusion if refractory
Dantrolene	Malignant hyperthermia, NMS (adjunct)	2.5 mg/kg, up to 10 mg/kg
Lipid emulsion 20%	LAST	1.5 mL/kg bolus + 0.25 mL/kg/min
Sodium bicarbonate	Na-channel blocker QRS widening	1 mEq/kg bolus, titrate to pH 7.5–7.55
Calcium gluconate/chloride	CCB, hyperK, Mg toxicity	IV, chloride 3x gluconate strength
Glucagon	Beta-blocker overdose	50 mcg/kg (3–5 mg) IV, then infusion
High-dose insulin/euglycemia	Refractory BB/CCB shock	1 U/kg bolus, 0.5–1 U/kg/h infusion + dextrose
Cyproheptadine	Serotonin syndrome	12 mg load, then 2 mg q2h
Bromocriptine	Neuroleptic malignant syndrome	2.5 mg enteral q6–8h
Benztropine / diphenhydramine	Acute dystonic reaction	1–2 mg IV/IM / 25–50 mg IV/IM
Atropine + pralidoxime	Organophosphate/carbamate	Doubling doses to dry secretions
Physostigmine	Anticholinergic toxidrome	0.5–1 mg IV/IM
NAC	Acetaminophen overdose	Weight-based, per nomogram
DigiFab	Digoxin toxicity	By ingested dose or level
Deferoxamine	Iron toxicity	Infusion, by serum iron level
Succimer / dimercaprol + CaEDTA	Lead poisoning	By BLL and encephalopathy status
Pyridoxine	INH-induced refractory seizures	Gram-for-gram, up to 5 g empiric
Leucovorin	Methotrexate toxicity	15 mg IV/PO q6h, per level
L-carnitine	Valproate hyperammonemia/hepatotoxicity	IV load + infusion, dose unsettled
Octreotide	Sulfonylurea overdose (not exogenous insulin)	50–100 mcg SC/IV q6–12h, with dextrose
Methylene blue	Methemoglobinemia / vasoplegic shock	1–2 mg/kg IV
100% oxygen ± HBOT	Carbon monoxide poisoning	Non-rebreather; HBOT contested, consider if severe
Hydroxocobalamin	Cyanide poisoning	5 g IV
Fomepizole	Methanol/ethylene glycol	Load then maintenance IV
CroFab	Pit viper envenomation	4–12 vials initial, by species/severity
Latrodectus antivenom	Black widow envenomation, severe	1 vial
Anascorp	Scorpion envenomation (Centruroides)	3 vials initial, then 1 vial q30–60min
Botulinum antitoxin / BabyBIG	Botulism	Via CDC/health department

Primary sources checked for this guide:

Abad-Gurumeta A, et al. Systematic review of sugammadex vs neostigmine for reversal of neuromuscular blockade. Anaesthesia. 2015.
Low-dose sugammadex vs neostigmine for reversal of moderate rocuronium block, RCT. 2025.
Penninga L, et al. Adverse events associated with flumazenil in benzodiazepine intoxication: systematic review with meta-analyses of RCTs. Basic Clin Pharmacol Toxicol. 2016.
Fatal seizures after flumazenil in mixed overdose. Case report reviewed via PubMed.
MHAUS. Dantrolene dosing, reconstitution, and recrudescence guidance.
Burkman JM, Posner KL, Domino KB. Clinical variables associated with recrudescence after MH reactions. Anesthesiology. 2007;106:901-906.
Neal JM, Neal EJ, Weinberg GL. ASRA checklist for treatment of local anesthetic systemic toxicity, 2020 update. Reg Anesth Pain Med. 2020.
A literature review of sodium bicarbonate for QRS widening. J Med Toxicol, reviewed via PubMed.
Pai V, et al. Optimising alkalinisation and its effect on QRS narrowing in TCA poisoning. Br J Clin Pharmacol. 2022.
Woodward C, Pourmand A, Mazer-Amirshahi M. High dose insulin therapy: an evidence-based approach to beta-blocker/CCB toxicity. 2014.
Schult RF, et al. Evaluation of HDIE therapy following guideline implementation. Am J Health Syst Pharm. 2022;79(7):547-555.
Serotonin Syndrome. StatPearls, cyproheptadine dosing and Hunter criteria. 2024.
Cyproheptadine in serotonin syndrome: a retrospective study. 2024.
Sakkas P, Davis JM, Janicak PG, Wang ZY. Drug treatment of the neuroleptic malignant syndrome. Psychopharmacol Bull. 1991;27(3):381-384.
An approach to the pharmacotherapy of neuroleptic malignant syndrome. 2019.
ACEP policy on N-acetylcysteine for acetaminophen overdose, reviewed via AFP.
Rumack-Matthew nomogram, original and revised treatment line. Pediatrics. 1975; subsequent revisions.
DigiFab prescribing information. FDA, accessed 2026.
Ekins BR, et al. Digoxin-specific antibody dosing strategy review. 2024.
Deferoxamine (Desferal) prescribing information and dosing thresholds. Medscape/StatPearls.
Succimer monograph and dosing. Drugs.com/LiverTox, 2020-2025.
With dimercaprol no longer manufactured, how should we treat severe lead poisoning? Tennessee Poison Center, 2023.
Bhargava M, et al. Comparison of two doses of leucovorin in severe low-dose methotrexate toxicity, RCT. 2023.
Leucovorin. StatPearls, dosing and rescue timing. 2026.
Gziut, et al. L-carnitine for valproic acid-induced toxicity. Br J Clin Pharmacol. 2025.
Boyle PJ, et al.; Octreotide's role in sulfonylurea-induced hypoglycemia, evidence review. J Med Toxicol. 2010.
Methylene blue for refractory vasoplegic shock, case reports and mechanism review. 2017, 2023.
Brent J, et al. Fomepizole for the treatment of methanol poisoning. N Engl J Med. 2001;344(6):424-429.
Adverse drug events with ethanol vs fomepizole for toxic alcohol poisoning, cohort study. 2009.
Medication errors with ethanol vs fomepizole, poison center comparison, reviewed via University of Utah Poison Control.
Crotaline Fab antivenom in severe North American pit viper envenomation: an integrative review. Clin Toxicol, reviewed via PMC.
Missouri Poison Center and University of Utah Poison Control antidote charts, cross-referenced for Latrodectus, botulinum antitoxin, physostigmine, and lead chelation dosing.
Weaver LK, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. N Engl J Med. 2002;347(14):1057-1067.
Scheinkestel CD, et al. Hyperbaric or normobaric oxygen for acute carbon monoxide poisoning: a randomised controlled clinical trial. Med J Aust. 1999;170(5):203-210.
Juurlink DN. Hyperbaric oxygen should not be used routinely for carbon monoxide poisoning. Br J Clin Pharmacol. 2023.
Hyperbaric treatment of carbon monoxide toxicity. StatPearls, 2023.
Anascorp (Centruroides scorpion antivenom) prescribing information. FDA, accessed 2026.
Curry SC, et al. Antivenom for severe scorpion envenomation in Arizona. N Engl J Med, correspondence, 2021.
Bark scorpion sting: indications for Anascorp and dosing controversies. Reviewed via ALiEM, 2018.
Anaphylaxis: acute management. World Allergy Organization / ACAAI joint guidance on IM epinephrine dosing and route, reviewed 2026.
Epinephrine for first-aid management of anaphylaxis. American Academy of Pediatrics clinical report, Pediatrics. 2017;139(3):e20164006.
AAP Committee on Drugs. Naloxone dosage and route of administration for infants and children. Pediatrics. 1990;86(3):484-485.
Atropine, flumazenil, glucagon, hydroxocobalamin, methylene blue, naloxone pediatric monographs. Atlantic Canada Poison Centre, reviewed 2026.
Calcium gluconate pediatric dosing. StatPearls / Drugs.com, reviewed 2025-2026.
Sodium bicarbonate pediatric dosing in TCA overdose and toxin-induced dysrhythmia. Atlantic Canada Poison Centre; RxDx pediatric toxicology guide, 2026.
Pediatric acetaminophen NAC dosing, including modified two-stage IV protocol. Reviewed via droracle.ai clinical reference, 2025.
Deferoxamine, atropine/pralidoxime pediatric dosing. NJ Poison Information and Education System Antidote Use Guideline, 2023.
Cyproheptadine pediatric dosing and overdose toxicity. Pediatric case report, 2018; pediatric dosing reference, 2025.
Hydroxocobalamin (Cyanokit) prescribing information, pediatric dosing. FDA label; Atlantic Canada Poison Centre; Maryland Poison Center ToxTidbits.
Sugammadex pediatric pharmacokinetic trials (birth to <2 years, and older cohorts). ClinicalTrials.gov NCT03351608, NCT03909165.
BabyBIG (botulism immune globulin) prescribing information and dosing. FDA; University of Utah Poison Control, 2026; California Department of Public Health Infant Botulism Treatment and Prevention Program.
Glucagon pediatric dosing for beta-blocker overdose. Atlantic Canada Poison Centre, reviewed 2026.