Why this poison is interesting

This is the page the antidote index has been waiting for. Phytomenadione, prothrombin complex concentrate, idarucizumab and andexanet alfa all have monographs on the sibling site and, until now, no poison in this library that they treat. The gap mattered: four antidotes that a UK emergency department reaches for regularly had no mechanism page pointing at them.

What makes the group worth a single entry is that it is the exact opposite of sodium-channel blockade. There, a dozen unrelated molecules converge on one lesion, and the treatment is aimed at the lesion, so it is the same for all of them. Here, four drugs converge on one clinical sign — bleeding — and the treatments are completely non-interchangeable. Vitamin K reverses warfarin and does nothing whatever to a factor Xa inhibitor; the rivaroxaban label says so in as many words.⁴ Idarucizumab binds dabigatran and no other drug in the class. Dialysis removes dabigatran and not the others. One syndrome, and antidotes that do not interchange — vitamin K for the two vitamin K antagonists, and something different for each of the direct inhibitors.

The second reason is timing, and it is the reason a warfarin overdose is dangerous to assess. Warfarin does not attack the clotting factors. It attacks the enzyme that makes them usable, and the factors already in circulation are unaffected. A patient may be poisoned, correctly assessed, and entirely normal on every test available — because the poisoning has not started yet.

A poison is a drug whose kinetics have escaped its pharmacology.

The toxic principle

Four mechanisms, and the differences between them predict everything else on this page.

Warfarin — a vitamin K antagonist: A synthetic anticoagulant of the coumarin series. It acts by inhibiting the formation of active clotting factors II, VII, IX and X, and has no direct effect on an established thrombus.¹ Read that carefully: it inhibits their formation. Factors already made and already carboxylated are untouched, and go on working until they are cleared. Established
The superwarfarin rodenticides: The same target reached by a molecule engineered to persist. Brodifacoum, difenacoum and bromadiolone are long-acting anticoagulant rodenticides, and the difference from warfarin is duration rather than mechanism — a reported plasma half-life of 56 days in one poisoned patient, with the drug detectable until day 209.⁶ Established
Rivaroxaban and apixaban — direct factor Xa inhibitors: They bind factor Xa itself. No enzyme is inhibited upstream, nothing has to be resynthesised, and the effect is present as soon as the drug is absorbed and gone as soon as it is cleared. Vitamin K is irrelevant to them by construction, which the rivaroxaban label states outright.⁴ Established
Dabigatran — a direct thrombin inhibitor: One step further down, binding thrombin rather than the enzyme that generates it. Its distinguishing property is not its target but its low protein binding, which is why it alone in this group can be dialysed.³ Established

Toxicokinetics

The table below deliberately mixes the four drugs, because the useful comparisons are across them rather than within any one.

Four anticoagulants — where they differ is where the management differs
Parameter	Therapeutic	In overdose	Why it changes
Warfarin — absorption	Readily absorbed from the gastro-intestinal tract; it can also be absorbed through the skin¹	Unchanged; the label sets an action threshold at more than 0.25 mg/kg or more than the patient's therapeutic dose within 1 hour¹	The dermal route is worth noticing on a page that includes rodenticides handled without gloves. The ingestion threshold above is the label's own trigger for considering charcoal¹ and is a when to act figure, not a toxic dose.
Warfarin — distribution and half-life	Extensively bound to plasma proteins; plasma half-life about 40 hours¹	Prolonged effect, but the drug's half-life is not the clinical clock	The most misleading number on the page. Extensive protein binding rules out dialysis, and the 40-hour half-life describes the drug rather than the coagulopathy — which persists as long as functional factors remain suppressed. Metabolism is by hepatic microsomal enzymes to inactive metabolites.¹
Superwarfarins	Same target; a reported brodifacoum plasma half-life of 56 days, first-order, undetectable at day 209 in one case⁶	Coagulopathy measured in weeks to months	The published kinetics genuinely disagree, and both reports are single cases. Olmos & López describe first order elimination with a 56-day half-life⁶; Bruno et al report a case in which brodifacoum appears to follow zero-order elimination pharmacokinetics⁷. Neither is a series, and the disagreement is recorded rather than resolved.
Apixaban	Half-life 13.4 hours administered alone²	Charcoal at 2 h reduced mean AUC by 50%, at 6 h by 27%, with no impact on Cmax; half-life fell to 5.3 h and 4.9 h respectively²	A quantified decontamination effect is rare enough in this library to be worth dwelling on. Note what it does and does not do: the peak is unchanged, so charcoal is shortening exposure rather than preventing it — consistent with interruption of enterohepatic or enteric recirculation rather than with blocking initial absorption.
Rivaroxaban	Half-life approximately 5 to 13 hours in adults, shorter in children on population modelling⁴	Exposure plateaus above 50 mg through limited absorption⁴	The only drug here whose overdose is self-limiting by physical chemistry. It does not make a bleeding patient safe — it makes the dose a poor guide to how bleeding they will be.
Dabigatran	Renally excreted predominantly; protein binding low³	Accumulates as renal function falls; adequate diuresis must be maintained³	The renal dependence and the low binding are the same fact seen twice. A drug that is not held by albumin is both filtered by the glomerulus and reachable by a dialyser.
Dialysability	—	Dabigatran: yes — as protein binding is low, dabigatran can be dialysed; there is limited clinical experience to demonstrate the utility of this approach³. Rivaroxaban: no — due to the high plasma protein binding rivaroxaban is not expected to be dialysable⁴. Apixaban: effectively no — haemodialysis decreased AUC by 14% in end-stage renal disease, so haemodialysis is unlikely to be an effective means of managing apixaban overdose². Warfarin: no, on the same protein-binding grounds¹	EXTRIP has addressed none of these drugs; its published recommendation index covers 22 poisons and contains no anticoagulant.¹⁰ Every statement in this row is therefore a manufacturer's, derived from protein binding and in dabigatran's and apixaban's case from measurement. This is an absence of assessment, not a recommendation against, and the distinction matters as much here as it does on the sodium-channel blockade page.

Metabolism and the metabolites

No anticoagulant here is bioactivated, and warfarin's metabolites are inactive.¹ The interesting chemistry is not in the drug's metabolism at all — it is in the cofactor cycle the drug interrupts, which is why the pathway below is drawn around vitamin K rather than around warfarin.

The vitamin K cycle, and the three places this group of poisons attacks the clotting cascade

Vitamin K (reduced)The cofactor for gamma-carboxylation of factors II, VII, IX and X
Functional factors II, VII, IX, XAlready-carboxylated factors are unaffected by anything on this page and go on working until cleared
Warfarin and the superwarfarinsBlock the regeneration of reduced vitamin K. Newly made factors are inert; the existing pool is untouched¹
Rivaroxaban, apixabanBind factor Xa directly. Nothing upstream is affected and nothing needs resynthesis²⁴
DabigatranBinds thrombin itself, one step below factor Xa³
Failure of thrombin generation — one clinical sign, four causesThe convergence is at the bedside, not in the biochemistry — which is exactly why the antidotes do not interchange

Why the antidote is the cofactor for one drug and a decoy for another

The shape of an antidote follows from where in the diagram the poison sits. Warfarin removes a cofactor from circulation, so the antidote is the cofactor — phytomenadione, given in enough excess to drive a partially blocked cycle. That takes hours, because the factors must then be synthesised and carboxylated. A direct inhibitor is a molecule bound to a protein, so the antidote must be a molecule that binds it better: idarucizumab for dabigatran, or a catalytically inactive decoy factor Xa in andexanet alfa. Prothrombin complex concentrate is the third possibility and the crudest — supply the missing product and bypass the argument entirely, which is why factor replacement appears in the overdose section of every label here — as PCC on three, and as coagulation factor concentrates on the dabigatran label¹²³⁴ — and works, imperfectly, against poisons with unrelated mechanisms. Inferred

Elimination and accumulation

Two accumulation problems on this page have nothing to do with each other. The direct inhibitors accumulate the way ordinary renally cleared drugs do — dabigatran especially, which is excreted predominantly by the renal route.³ The superwarfarins accumulate on a scale that has no parallel anywhere else in this library.

A single ingestion that outlasts the admission by months

Brodifacoum and its relatives are warfarin's target with a lipophilic tail, and a single ingestion can anticoagulate for months: Olmos & López measured a 56-day half-life with the drug still detectable at day 209 in one poisoned patient.⁶ Chua & Friedenberg's series of 11 records two cases in which patients were examined and treated for months before establishing a diagnosis and fully reversing the anticoagulation — though these were factitious ingestions, so those months reflect repeated dosing and diagnostic delay as much as one drug's persistence — and it concludes that superwarfarin belongs in the differential for any vitamin K-dependent coagulopathy that does not resolve with large doses of parenteral vitamin K1 therapy.⁸ Bruno's case required oral vitamin K1 at approximately 7 mg/kg per 24 hours in divided doses⁷ — well over an order of magnitude beyond a warfarin reversal dose. The treatment is not a reversal; it is a continuous replacement of a cycle that is still blocked. Established

The UK relevance is not theoretical, and it links this page to one that already exists. In March and April 2018 more than 150 patients presented to Illinois hospitals with coagulopathy and bleeding after synthetic cannabinoid use. In the 34 patients reported in detail, confirmatory anticoagulant testing was performed in 15 and superwarfarin poisoning was confirmed in all 15 — brodifacoum in 15 (100%), difenacoum in 5 (33%), bromadiolone in 2 (13%) and warfarin in 1 (7%). Gross haematuria was present in 19 of 34 (56%) and abdominal pain in 16 (47%); one patient died of complications of spontaneous intracranial haemorrhage.⁵ A poisoning nobody had taken deliberately, diagnosed only because someone tested for it. See synthetic cannabinoids, the page for the drug these patients believed they were using.

Charcoal that works on the way out rather than on the way in

The apixaban figures repay a second look. In healthy subjects, charcoal given 2 hours after a 20 mg dose reduced mean AUC by 50%, and at 6 hours by 27% — but had no impact on Cmax at either time, while the half-life fell from 13.4 h to 5.3 h and 4.9 h.² Apixaban's peak comes at 3 to 4 hours², so the 6-hour dose was given well after absorption was complete — and it still cut the AUC and shortened the half-life. A charcoal dose that only blocked absorption should do little once the peak has passed. An agent that shortens the half-life is acting on drug that has already been absorbed, which is the signature of interrupted recirculation rather than of decontamination. The label draws only the practical conclusion — that charcoal may be useful in the management of apixaban overdose or accidental ingestion² — and this page's mechanistic reading of it is an inference. Inferred

Target organs — and why those

Brain

TargetNo receptor. A vascular compartment with no room to accommodate a haematoma

Why hereNone of these drugs is neurotoxic and none reaches a target in the brain. The brain is the organ that matters because it is enclosed: a volume of bleeding that would be trivial in muscle is lethal inside a fixed box, and there is no tamponade and no compressible surface. Organ selectivity here is not pharmacological but anatomical — the poison does not choose the brain, the anatomy does. The Illinois series records one death, from complications of spontaneous intracranial haemorrhage.⁵ Established

At the bedsideIntracranial haemorrhage is the presentation that converts an anticoagulant into an emergency. It is the reason reversal exists as a concept, and the reason the time an antidote takes to work is a clinical variable rather than a pharmacological detail.

Gastrointestinal tract

TargetMucosal surface with pre-existing lesions that are normally sealed by haemostasis

Why hereThe commonest site of major anticoagulant bleeding, and it is selected by the same logic in reverse: a large, thin, chronically injured surface whose small erosions are continuously and invisibly repaired by clot formation. Remove the repair and pre-existing pathology becomes a haemorrhage. The poison does not create the lesion; it removes the mechanism that was concealing it. Inferred

At the bedsideMelaena, haematemesis, a falling haemoglobin without an obvious source. Worth noting that tranexamic acid is not a general answer here — the trauma literature's timing rules do not transfer to gastrointestinal bleeding, and the rivaroxaban label records only limited experience with it.⁴

Kidney and urinary tract

TargetNot injured by the drug; the site where a minor bleed becomes visible first

Why hereThis card exists because of a measurement rather than a mechanism. Gross haematuria was the commonest presenting symptom in the Illinois superwarfarin outbreak — 19 of 34 patients (56%), with renal abnormalities on CT in 12 of those imaged for abdominal pain.⁵ The urinary tract is where a coagulopathy announces itself cheaply, because a small amount of blood changes the colour of a large volume of urine. Established

At the bedsideVisible haematuria, often the first sign and often dismissed. In the superwarfarin context it was the finding that led to testing at all.

The liver — as the factory, not the casualty

TargetHepatic synthesis of factors II, VII, IX and X, and the vitamin K cycle within it

Why hereIncluded deliberately as a non-target, on the same principle as the kidney card on the gabapentinoids page. Warfarin is not hepatotoxic; the liver appears because it is where the poison acts and where the antidote must work. Phytomenadione does not reverse anything directly — it restores a cofactor so that the liver can make functional factors again, which takes as long as synthesis takes. This is why prothrombin complex concentrate exists: it is the answer to an organ that cannot be hurried. Established

At the bedsideNothing to examine. The clinical consequence is temporal: vitamin K alone cannot correct a coagulopathy faster than the liver can synthesise, which is the whole argument for giving factors in life-threatening haemorrhage.¹

Timeline of effects

Warfarin overdose — the poisoning that has not started when the patient arrives

Time

What you seeWhat is happening

0–4 hAbsorption
What you seeEntirely well. INR normal. No bleeding, no sign of anything.
What is happeningWarfarin readily absorbed¹ and already at its target. The circulating factors are fully carboxylated and completely functional, so no test of coagulation can be abnormal yet.
4–24 hThe gap
What you seeStill well, and still testing normal or nearly so. The most dangerous appearance in this poisoning.
What is happeningSynthesis of new factors is inert, but the existing pool has not yet decayed. The interval is set by the factors' clearance, not by the drug's half-life — which is why the label demands sequential INRs rather than one.¹ Factor VII, with the shortest survival of the four, decays first, so the INR moves before any antithrombotic effect is complete.
24–48 hThe INR rises
What you seeCoagulopathy appears. Bleeding may or may not accompany it.
What is happeningThe functional factor pool has fallen far enough to be measured. The label directs measurement at presentation and sequentially every 24–48 hours after ingestion, and monitoring for at least 48 hours post overdose.¹ A patient discharged on the strength of a normal INR at four hours has been discharged before the poisoning.
DaysWarfarin resolution
What you seeINR falls as the drug is cleared and synthesis resumes.
What is happeningWarfarin half-life about 40 hours¹; recovery requires both drug clearance and new factor synthesis, which is why reversal with vitamin K alone is measured in hours rather than minutes.
Weeks to months — superwarfarins onlyThe tail that does not end
What you seeRecurrent coagulopathy whenever vitamin K is stopped.
What is happeningA brodifacoum half-life reported at 56 days, with drug detectable to day 209 in one case⁶, and high-dose oral vitamin K1 required in another⁷. Chua & Friedenberg treated two factitious ingestions for months before the diagnosis was made.⁸ The cycle is still blocked long after the ingestion is history.

A gap made of protein that is still working

Anticoagulants — clotting factors that were already made, still working — the poison stops production and nothing happens until the existing stock decays

The other 28 kinds of latent phase in this library

Amphetamines and MDMA — a hormone acting normally on a kidney behaving normally, while the patient supplies the water
Antipsychotics — a physical object in the stomach — extended-release quetiapine forming a pharmacobezoar
Arsenic — a tissue declaring on its own timetable rather than the poison's — the arsenic is excreted within days, but the nail that was growing while it circulated does not show its white transverse line for several weeks
Arsine and stibine — a red cell mass haemolysing faster than a kidney can cope with — the exposure is over, the haemolysis is silent until the urine changes colour, and the renal failure that follows is the cause of death
Baclofen — not the poisoning but its withdrawal — an implanted pump that has silently stopped delivering, with hours to days before anything appears
Beta-blockers — a repolarisation lesion waiting for an ectopic beat to fall inside it — sotalol prolongs the QT and then, for hours, nothing happens
Calcium-channel blockers — a tablet that has not yet dissolved
Carbon monoxide — an inflammatory process continuing after the poison itself has gone
Chlorine and ammonia — paraquat's cause at its shortest — the time an injured alveolar epithelium takes to leak
Cocaine — a package that has not yet failed — the calcium-channel blocker's cause moved outside the tablet, where wrapping integrity cannot be measured
Digoxin — distribution of the drug to its target — which that page argues is not a latent phase in the paracetamol sense at all
Ethylene glycol — paracetamol's cause with a different enzyme — glycolate accumulating behind glycolate oxidase while the patient looks merely drunk
GHB and GBL — not the poisoning but its withdrawal — a half-life under an hour means admission for any reason interrupts round-the-clock redosing
Hydrofluoric acid — an ion diffusing far enough to reach a nerve ending — and the thinner the solution, the further it travels before anybody feels it
Iron — a true remission — the corrosive injury settling while absorbed iron moves into the cells it will poison, so the patient improves on their way to the dangerous phase
Ketamine — nitrous oxide's cause on a longer clock — urothelial damage accumulating over months to years of repeated exposure
Lead — bone giving lead back — a store with a half-life of 10 to 30 years releasing its contents when pregnancy, lactation, menopause or osteoporosis resorbs it, so the blood concentration rises after the exposure has ended
Lithium — transport across cell membranes
Mercury — distribution on two clocks — tissue concentrations peaking within 24 hours everywhere except the brain, which is not reached until 2 to 3 days, and which then cannot let the poison out again
Methaemoglobin inducers — paracetamol's cause at its shortest — one to four hours manufacturing the toxic species
Methanol — paracetamol's cause again — formate accumulating behind a folate-dependent disposal step that primates perform poorly
Nitrous oxide — damage accumulating to a threshold
Opioids — an antidote wearing off before the poison does — renarcotisation, the only gap in this set that treatment creates rather than reveals
Organophosphate insecticides — a fat store emptying — and, separately, a second and unexplained lesion declaring itself at a neuromuscular junction the first phase had already left
Paracetamol — time spent manufacturing a toxic metabolite
Paraquat — the body responding to an injury that is already complete
Sodium-channel blockade — a gap that cannot be shortened
Thallium — hair on its own clock rather than the poison's — sensory symptoms come first and the alopecia that makes the diagnosis obvious follows them, well after the interval in which treatment is recommended

Nothing is being manufactured, nothing is dissolving, nothing is diffusing and nothing is being distributed. The poison is already at its target and fully effective; what fills the gap is the continued function of protein that was made before it arrived. It is drawn as a hole because during it every test is normal and the patient is genuinely not yet poisoned — and it closes not when the drug does something, but when the factors run out.

What the mechanism predicts at the bedside

A normal INR shortly after a warfarin ingestion means nothing at all. The label requires sequential measurement every 24–48 hours and monitoring for at least 48 hours.¹ This is the single most useful sentence on the page.
A normal INR means nothing after a DOAC either, for the opposite reason — the INR is not the right test for a direct inhibitor. Dabigatran's label points to a calibrated quantitative dTT test or repeated dTT measurements to predict when concentrations will fall, also in case additional measures e.g. dialysis have been initiated.³
Establish which drug it is before reaching for an antidote, because they do not interchange. Protamine sulphate and vitamin K are not expected to affect the anticoagulant activity of rivaroxaban.⁴ Giving vitamin K for a factor Xa inhibitor is not a cautious choice; it is an ineffective one.
Only dabigatran is dialysable, and it is dialysable because of protein binding rather than because of its target.³ Rivaroxaban is not expected to be⁴; haemodialysis reduced apixaban AUC by 14%.²
Charcoal has real, quantified value for apixaban, including a dose given after the peak — AUC still cut 27% at 6 hours, past the 3–4 h peak, with the half-life shortened² — and is worth considering for rivaroxaban⁴ and, at the label's stated threshold, for warfarin.¹
A very large rivaroxaban ingestion is not proportionally worse, because absorption ceilings above 50 mg in adults.⁴ This does not apply to children, in whom the label says there are no data.⁴
A coagulopathy that will not stay reversed is a superwarfarin until disproved. Chua & Friedenberg's conclusion is exactly this: consider it in any vitamin K-dependent coagulopathy without warfarin, liver disease or an inhibitor, that does not resolve with large doses of parenteral vitamin K1.⁸
Ask about recreational drug use in unexplained coagulopathy. In the Illinois outbreak the patients believed they had taken a synthetic cannabinoid; brodifacoum was found in 15 of 15 tested.⁵
Vitamin K takes hours because the liver has to make the factors. In life-threatening haemorrhage the label reaches for prothrombin complex concentrate (or fresh frozen plasma) first¹; vitamin K, which the label gives in its less severe tiers¹, is added in practice — the factors supply the present, the vitamin supplies the future.
Warfarin can be absorbed through the skin¹, which is worth remembering when the exposure is occupational or a rodenticide handled without gloves.

The antidote, from the poison's side

This group has more real antidotes than any other page in the library, and they illustrate three genuinely different strategies. Doses for all of them are on the sibling site and in TOXBASE; what follows is what each one is for.

Phytomenadione — replace the cofactor: Vitamin K1 floods a partially blocked cycle so that carboxylation can resume. It treats the cause and therefore works slowly, because the liver must then synthesise. It is useless against every direct inhibitor.⁴ The warfarin label also warns that large doses may completely reverse the effects of warfarin and make re-establishment of anticoagulation difficult¹ — an antidote whose success can itself be a problem.
Prothrombin complex concentrate — supply the product: PCC contains factors II, VII, IX and X and bypasses both the enzyme and the wait. Factor replacement appears in the overdose section of every label here — named as PCC on three and as coagulation factor concentrates on the dabigatran label¹²³⁴ — which is remarkable for an agent with four different mechanisms in front of it — and its evidence is correspondingly uneven. For apixaban the label reports that reversal of pharmacodynamic effect was evident at the end of infusion in healthy subjects, immediately followed by: however, there is no clinical experience with the use of 4-factor PCC products to reverse bleeding in individuals who have received apixaban.²
Idarucizumab — bind the drug: Idarucizumab is a monoclonal antibody fragment against dabigatran, named on the label as the specific reversal agent... antagonizing the pharmacodynamic effect of dabigatran, with efficacy and safety not established in paediatric patients.³ The purest bind-the-drug strategy on this page — an antibody fragment against the poison itself, the same approach as digoxin immune Fab in digoxin poisoning.
Andexanet alfa — offer a decoy: Andexanet alfa is a modified factor Xa that binds the inhibitor without doing factor Xa's job. Rivaroxaban's label names it as available for adults but not established in children⁴; apixaban's refers to a reversal agent for factor Xa inhibitors.² A third strategy entirely: neither replacing the cofactor nor supplying the product, but removing the poison by giving it something else to bind.
Haemodialysis — for dabigatran alone: Reachable only because dabigatran's protein binding is low.³ The label is candid that there is limited clinical experience to demonstrate the utility of this approach.³
Activated charcoal: Quantified for apixaban², suggested for rivaroxaban⁴, and threshold-triggered for warfarin.¹ The best-evidenced decontamination on any page in this library, and it is on the page where decontamination matters least in the moment.
What does not work: Vitamin K and protamine against rivaroxaban.⁴ The label also records neither scientific rationale for benefit nor experience with desmopressin, and no experience with aminocaproic acid or aprotinin.⁴ A list of negatives on a label is worth as much as the positives.

The reflex that the evidence does not support

A raised INR without bleeding provokes a strong urge to give vitamin K, and the warfarin label supports it above an INR of 8.0 for patients on long-term therapy.¹ A systematic review and meta-analysis of six randomised trials in 1,074 participants with INR between 4.5 and 10 and no bleeding found a non-significant increase in mortality (RR 1.42, 95% CI 0.62–2.47), bleeding (RR 2.24, 0.81–7.27) and thromboembolism (RR 1.29, 0.35–4.78) with vitamin K, and a non-significant increase in reaching goal INR (RR 1.95, 0.88–4.33); the authors conclude such patients are not likely to benefit from vitamin K administration in addition to temporary VKA cessation, at moderate certainty for the harm outcomes.⁹ The claim that a high INR without bleeding needs vitamin K is downgraded here to traditional teaching — a treatment-efficacy downgrade under the exemption stated in this site's README, structurally identical to the beta-blocker and glucagon badge. Note the scope carefully. It says nothing about the bleeding patient, nothing about an INR above 10, and nothing about acute overdose in a patient not previously anticoagulated, for whom the label's separate pathway applies.¹ Traditional teaching

Critical appraisal

The vitamin K cycle account is standard biochemistry and is not cited to a primary source here. The label supplies only that warfarin inhibits the formation of active clotting factors II, VII, IX and X.¹ The carboxylation step, the epoxide reductase and the cofactor recycling are textbook and uncontested, and are badged established on that basis — the same treatment the organophosphate page gives thion-to-oxon bioactivation, and it carries the same risk. If an auditor cannot source the cycle, the antidote logic on this page is affected rather than a sentence.
The factor VII argument is the weakest link in the timeline and is deliberately kept short. That factor VII has the shortest survival of the four and therefore moves the INR before the antithrombotic effect is complete is universally taught; no factor half-life is printed on this page, because none could be verified from a source cited here. The clinical instruction the page actually relies on — sequential INRs, at least 48 hours — is the label's own.¹
The superwarfarin kinetics rest on two single case reports that disagree with each other, and the page says so in the kinetics table rather than choosing one. Olmos & López report first-order elimination with a 56-day half-life⁶; Bruno et al report apparent zero-order elimination.⁷ Neither is a series, and no half-life for brodifacoum should be treated as a population value.
The Illinois figures are from a single-centre case series within a larger outbreak — 34 patients at one medical centre, of whom only 15 had confirmatory testing, and the authors state that the specific synthetic cannabinoid compounds are not known.⁵ The 100% brodifacoum positivity is 15 of 15 tested, not 15 of 34, and the page prints it that way.
The charcoal-shortens-half-life mechanism is this page's inference, not the label's claim. The figures are the label's and are exact.² The reading that an unchanged Cmax with a halved AUC and a shortened half-life indicates interrupted recirculation rather than blocked absorption is badged inferred for that reason.
The vitamin K badge is scoped narrowly and should be attacked at its edges. Khatib's population is INR 4.5–10 without bleeding on VKA therapy.⁹ The warfarin label's threshold for the same population is INR >8.0¹, so the two overlap between 8 and 10 rather than contradicting each other across the whole range. The badge is on the general teaching, not on the label, and an auditor who concludes it should be narrower still would be making a reasonable argument.
No figure on this page is attributed to TOXBASE, and no reversal dose of any antidote is printed, including the ones the warfarin label supplies in full.¹ The single dose figure that does appear — 7 mg/kg/24 h of oral vitamin K1 — is from a case report⁷ and is presented as what one patient required, to convey the scale of the problem, not as a regimen.
EXTRIP has assessed none of these drugs, and the page cites its index for that absence¹⁰ rather than inferring a recommendation from silence. The dialysability statements are manufacturers' and are attributed as such.
Andexanet alfa's licensed scope is narrower than a reader might assume from this page's symmetry. It is named on the rivaroxaban label as available for adults and not established in children⁴; nothing here should be read as a statement about which bleeding sites it is indicated for, which is a question the labels cited do not answer.

References

1
Marevan 0.5 mg Tablets (warfarin sodium) — Summary of Product Characteristics. electronic medicines compendium, product 2803. Sections 4.9 (Overdose), 5.1 (Pharmacodynamic properties) and 5.2 (Pharmacokinetic properties). medicines.org.uk/emc/product/2803
2
Eliquis 5 mg film-coated tablets (apixaban) — Summary of Product Characteristics. electronic medicines compendium, product 2878. Section 4.9 (Overdose). medicines.org.uk/emc/product/2878
3
Pradaxa 150 mg hard capsules (dabigatran etexilate) — Summary of Product Characteristics. electronic medicines compendium, product 4703. Section 4.9 (Overdose). medicines.org.uk/emc/product/4703
4
Xarelto 20 mg film-coated tablets (rivaroxaban) — Summary of Product Characteristics. electronic medicines compendium, product 2793. Section 4.9 (Overdose, including Management of bleeding). medicines.org.uk/emc/product/2793
5
Kelkar AH, Smith NA, Martial A, et al. An Outbreak of Synthetic Cannabinoid-Associated Coagulopathy in Illinois. New England Journal of Medicine 2018 Sep 27;379(13):1216–1223. PMID 30280655. A single-centre case series of 34 patients within a larger outbreak; confirmatory testing performed in 15.
6
Olmos V, López CM. Brodifacoum poisoning with toxicokinetic data. Clinical Toxicology (Philadelphia) 2007 Jun–Aug;45(5):487–9. PMID 17503253. A single case report — first-order elimination, 56-day half-life, undetectable at day 209.
7
Bruno GR, Howland MA, McMeeking A, et al. Long-acting anticoagulant overdose: brodifacoum kinetics and optimal vitamin K dosing. Annals of Emergency Medicine 2000 Sep;36(3):262–7. PMID 10969235. A single case report — apparent zero-order elimination, and the source of the 7 mg/kg/24 h oral vitamin K1 figure quoted as one patient's requirement.
8
Chua JD, Friedenberg WR. Superwarfarin poisoning. Archives of Internal Medicine 1998 Sep 28;158(17):1929–32. PMID 9759690. Eleven cases; two factitious ingestions treated for months before diagnosis.
9
Khatib R, Ludwikowska M, Witt DM, et al. Vitamin K for reversal of excessive vitamin K antagonist anticoagulation: a systematic review and meta-analysis. Blood Advances 2019 Mar 12;3(5):789–796. PMID 30850385. Six randomised trials, 1,074 participants, INR 4.5–10 without bleeding. The citation for the doubt behind this page's one evidence-tier downgrade.
10
EXTRIP Workgroup — published recommendations index. Extracorporeal Treatments in Poisoning Workgroup. Cited for the absence of any recommendation covering warfarin, the direct oral anticoagulants or the anticoagulant rodenticides. extrip-workgroup.org/recommendations

Anticoagulants

At a glance