Why this poison is interesting

Thallium is the most complete impersonation in a band built around impersonation. Its charge and ionic radius are close enough to potassium's that it is handled as potassium — Hoffman's review describes it entering cells "by a unique process governed by its similarity in charge and ionic radius to potassium".² Potassium transport is not a specialised system confined to one organ; it operates at the membrane of every cell in the body. A poison that travels on it therefore has no tissue it cannot reach, which is why thallium is "rapidly and nearly completely absorbed by virtually all routes"² and why the resulting illness has no anatomical focus.

The second reason is that thallium inverts the expectations built by the rest of this band. Every other metal page here reaches for a dithiol chelator. On this page they are not merely ineffective but harmful: "strong evidence speaks against the use of traditional metal chelators such as dimercaprol (British Anti-Lewisite) and penicillamine, and the latter may cause redistribution of thallium into the central nervous system".² The obvious physiological manoeuvre is also wrong — "forced potassium diuresis appears harmful"² — despite following directly from the potassium mechanism the page has just explained. A correct mechanism can generate a harmful treatment, and thallium is this library's clearest instance of it.

The third is that thallium is the first page since Band B able to cite an EXTRIP recommendation rather than an absence. Fifteen live pages in this library cite the workgroup's index to establish that a poison has not been addressed. Thallium has been, and the recommendation set is unusually complete — a general recommendation, two independent indications, a timing statement, cessation criteria and a modality preference.¹ Every single one of them is graded D, which is the lowest quality of evidence the system recognises, and that combination of strong recommendation on very weak evidence is itself the most interesting thing about the guidance.

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

The toxic principle

The entry mechanism is settled and the damage mechanism is not, and the page keeps those two things apart because the sources do. Hoffman states the first without hedging: thallium "enters cells by a unique process governed by its similarity in charge and ionic radius to potassium".² What happens next is stated with an explicit caveat attached: "Although the exact mechanism of toxicity has not been established, thallium interferes with energy production at essential steps in glycolysis, the Krebs cycle, and oxidative phosphorylation. Additional effects include inhibition of sodium-potassium-adenosine triphosphatase and binding to sulfhydryl groups."*² Traditional teaching

Why the account is plural, and why that is a finding rather than a gap in this page

Notice the shape of that sentence. It offers three mechanisms — interference with energy production at three separate points, inhibition of the sodium-potassium pump, and thiol binding — introduced by a statement that the mechanism has not been established. A list of candidate mechanisms is what a field produces when it has not settled on one. This is the same situation as arsenic, where the review supplying the mechanism says in the same abstract that the exact mechanism is not known. Both pages badge the account rather than presenting it as demonstrated, and on both pages the badge is carried by a direct statement in the source rather than by an absence of evidence — which is what this library's rule requires.

There is one further consequence of the potassium resemblance that is worth separating from the toxicity. Thallium is not confined by any of the barriers that normally limit a poison's distribution. It is absorbed nearly completely by all routes,² and it "crosses the placenta freely and produces abnormalities in animals as well as fetal demise, overt toxicity and congenital abnormalities in humans".² A poison that moves on potassium's machinery inherits potassium's access, and potassium goes everywhere.

Toxicokinetics

Two numbers dominate the table and they pull in opposite directions. Absorption is near-total, so there is no margin from incomplete uptake. Elimination has a half-life of several days, so there is a long window in which an intervention could in principle act — and that combination is the entire argument for the EXTRIP recommendation.

Thallium — near-complete absorption against an elimination half-life measured in days
Parameter	Therapeutic	In overdose	Why it changes
Absorption	—	"Rapidly and nearly completely absorbed by virtually all routes", ingestion being the commonest route producing toxicity²	No route offers protection. Decontamination has a narrow window and the absorbed fraction is effectively the exposed fraction
Cellular entry	—	"A unique process governed by its similarity in charge and ionic radius to potassium"²	Potassium transport is universal, so distribution is universal. There is no compartment thallium is excluded from
Placental transfer	—	"Crosses the placenta freely", with fetal demise, overt toxicity and congenital abnormalities reported in humans²	The same lack of a barrier, applied to the one membrane most poisons are partly held back by
Serum half-life	—	3.8 to 5.7 days by nonlinear regression in five patients receiving treatment, with "an approximate first-order elimination pattern"⁴	Slow enough that extracorporeal removal is coherent, which is unusual in this band. Note these were treated patients — this is elimination under therapy, not natural clearance
Distribution	—	Intracellular, following potassium²	The obstacle to any extracorporeal technique. A dialyser can only clear what is in the plasma, and thallium's plasma fraction is continually resupplied from cells rather than being the bulk of the burden
Recycling	—	Enterohepatic and enteroenteric circulation is the rationale for oral binders²	Why an oral agent works on a systemically distributed poison — the gut lumen is a compartment thallium keeps re-entering
Response to potassium loading	—	"Forced potassium diuresis appears harmful"²	The mechanism predicts this manoeuvre and the evidence refuses it. Raising potassium mobilises thallium out of cells, and mobilising it does not mean removing it
Dialysability	—	EXTRIP recommends ECTR in severe poisoning (1D); intermittent haemodialysis preferred, intermittent haemoperfusion or continuous renal replacement modalities valid alternatives (1D)¹	The only yes in this band. The recommendation is strong and the evidence behind it is graded D throughout

Metabolism and the metabolites

There is no metabolism and there is no metabolite. Thallium is an element that arrives as an ion and acts as that ion. This puts it with lithium and the rest of this band in the small group of poisons where nothing has to happen before harm begins — no activation, no bioactivation step to block, and correspondingly no enzyme an antidote could inhibit. Every therapeutic option on this page is therefore about removal, which is a narrower set of options than most pages in this library have.

Thallium — a pathway with no chemistry in it, only transport

Thallous salt, ingested"Rapidly and nearly completely absorbed"² — the active species as supplied
Absorption across the gut, essentially complete²
PlasmaA transit compartment rather than a reservoir — and the only compartment a dialyser can reach
Cellular uptake on potassium's transporters — "similarity in charge and ionic radius to potassium"²
Intracellular thallium, in every tissueNo sanctuary and no selectivity. The clinical picture is decided by which cells tolerate the disruption least, not by where the poison goes
Interference with energy production"At essential steps in glycolysis, the Krebs cycle, and oxidative phosphorylation"²
Inhibition of Na+/K+-ATPase and thiol bindingListed as "additional effects"² — candidates rather than a settled account
Enterohepatic and enteroenteric recycling — the loop an oral binder interrupts²
Slow elimination, serum half-life 3.8–5.7 days under treatment⁴The poison leaves over weeks; the axon does not recover on that schedule⁴

Elimination and accumulation

Thallium's elimination is the slowest thing about it that can still be measured usefully. A 2026 series of five patients with confirmed acute poisoning found "an approximate first-order elimination pattern, with an estimated serum half-life ranging from 3.8 to 5.7 days".⁴ That is slower than arsenic's three to five days only marginally — but arsenic is cleared renally from a body that distributes it into tissue reversibly, whereas thallium sits inside cells behind a transporter that put it there deliberately.

The finding that reframes everything else on this page

The same series followed all five patients for a year. "Electrophysiological studies revealed distal axonal neuropathy characterized by reduced compound muscle action potential amplitudes. At one-year follow-up, residual axonal involvement persisted in some patients."⁴ The authors' conclusion is the important sentence: "Persistent electrophysiological abnormalities despite declining thallium levels suggest incomplete neurological recovery."⁴ Falling thallium concentrations and a recovering patient are not the same thing, and on this page they demonstrably come apart. This is a five-patient series and is presented as one — but it is longitudinal, it is recent, and it measures the outcome that matters rather than the concentration that is easy to measure.

That decoupling is also the strongest argument for the urgency in the EXTRIP timing recommendation. If the injury is axonal and incompletely reversible, then removing thallium matters most before the axon is damaged, not after the concentration is high. The guidance says exactly that: "ECTR should be initiated as soon as possible, ideally within 24–48 hr of Tl exposure (1D)".¹

Where this latent phase sits among the others

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

The other 26 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
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's gap is arsenic's cause — a tissue declaring on its own clock — and the two pages are the only members of the set built on that. The distinctive feature here is the ordering, which is now measured rather than asserted: in the 2026 series "sensory symptoms generally preceded the onset of alopecia".⁴ The sign that makes the diagnosis obvious arrives after the sign that makes it possible, which is why a painful ascending sensory neuropathy of unclear cause is the moment to think of thallium — not the moment the hair falls out.

Target organs — and why those

A poison distributed by potassium's machinery reaches everything, so the organ list is not a list of places thallium goes. It is a list of tissues that tolerate a disruption of energy metabolism least well, and it is much shorter than the distribution would predict.

Peripheral nerve

TargetDistal sensory and motor axons

Why hereThe organ that defines the poisoning, and the one with least reserve. A long axon must maintain a membrane potential and an axonal transport system over a metre of distance, continuously, on locally generated ATP — so a poison that both disrupts energy production and inhibits the sodium-potassium pump² strikes it at two points at once. The injury is axonal rather than demyelinating, which is why it recovers slowly and sometimes incompletely. Inferred

At the bedside"A rapidly progressive, ascending, extremely painful sensory neuropathy."² Electrophysiologically, "distal axonal neuropathy characterized by reduced compound muscle action potential amplitudes", with residual involvement persisting in some patients at one year.⁴ The pain is the discriminating feature — it is disproportionate, it is early, and it precedes the alopecia.⁴

Hair follicle

TargetThe anagen follicle, a tissue in continuous rapid division

Why hereThe most famous sign in metal toxicology, and diagnostically it arrives late. A follicle in anagen is among the most metabolically demanding structures in the body; a poison that impairs ATP production stops it. The delay is not a delay in injury but in appearance — the follicle is struck early and the hair takes time to be shed. Inferred

At the bedsideAlopecia, listed with the neuropathy as one of the two "major manifestations of toxicity".² "Sensory symptoms generally preceded the onset of alopecia" in the 2026 series.⁴ Alopecia therefore confirms a diagnosis rather than opening a treatment window — it follows the sensory symptoms,⁴ which themselves follow the 24-to-48-hour interval in which extracorporeal treatment is recommended.¹

Gastrointestinal tract

TargetGut, but in the opposite direction to the rest of the band

Why hereIncluded precisely because it does not behave as a metal poisoning is expected to, and the source draws the contrast itself. Established

At the bedside"Unlike exposure to most metal salts, gastrointestinal symptoms of thallium toxicity are relatively minor, and constipation is more characteristic than diarrhoea."² This is a genuinely useful negative. Profuse diarrhoea points towards acute arsenic; relative gastrointestinal quiet with a severe painful neuropathy points here.

Autonomic and cranial nerves

TargetAutonomic ganglia and cranial nerves

Why hereGrouped by the source with the less specific findings, and grouped that way here rather than promoted. Nerve tissue again, and the same reasoning applies — but the evidence supporting these as characteristic features is weaker than for the distal sensory neuropathy. Inferred

At the bedside"An autonomic neuropathy, cranial nerve abnormalities, altered mental status, motor weakness, cardiac, hepatic, and renal effects are described, but are less specific."² The source's own hedge is retained — these broaden the differential rather than narrowing it.

Timeline of effects

Thallium — the diagnostic sign arrives after the treatment window

Time

What you seeWhat is happening

EarlyA quiet gut
What you seeGastrointestinal symptoms "relatively minor", with constipation more characteristic than diarrhoea.² There may be very little to find, and what there is does not suggest a metal.
What is happeningNear-complete absorption is occurring with almost no local mucosal signal.² The absence of a dramatic gastrointestinal phase removes the prompt that other metal poisonings supply.
Within 24–48 hThe window EXTRIP names
What you seeOften still non-specific. Diagnosis at this stage depends on the history or on a high index of suspicion.
What is happeningThis is the interval in which extracorporeal removal is recommended — "as soon as possible, ideally within 24–48 hr of Tl exposure (1D)".¹ The recommendation is explicitly not conditional on a concentration being available: exposure "highly suspected on the basis of history or clinical features" is itself an indication (2D).¹
DaysThe painful neuropathy
What you see"A rapidly progressive, ascending, extremely painful sensory neuropathy."² In the 2026 series, all five developed peripheral neuropathy, and sensory symptoms "generally preceded" alopecia.⁴
What is happeningAxonal injury in the tissue with the least metabolic reserve. The authors suggest "peripheral neuropathic symptoms may serve as an early clinical indicator of thallium poisoning"⁴ — this is the presentation to recognise, because the next one is too late to act on.
After the neuropathyAlopecia
What you seeHair loss — the sign that makes the diagnosis obvious to everyone, including the patient.
What is happeningThe follicle was injured days earlier; the hair takes time to be shed. Concentrations fall progressively during treatment,⁴ so by this stage the level is unlikely to be at its peak. The gap is a property of hair growth, not of the poison — the same structure as arsenic's nail lines.
Up to a yearIncomplete recovery
What you see"At one-year follow-up, residual axonal involvement persisted in some patients."⁴
What is happening"Persistent electrophysiological abnormalities despite declining thallium levels suggest incomplete neurological recovery."⁴ The poison and the disability are on different timescales, which is the strongest argument for treating early rather than treating hard.

What the mechanism predicts at the bedside

A severe, painful, ascending sensory neuropathy with a relatively quiet abdomen is the presentation to recognise.² Waiting for alopecia means waiting past the interval in which the recommended intervention is meant to start.^1,4
Constipation rather than diarrhoea distinguishes thallium from the rest of this band.² Acute arsenic causes profuse diarrhoea; lead causes colic and constipation but a motor-predominant neuropathy.
Do not wait for a thallium concentration before seeking advice. EXTRIP makes suspicion itself an indication: extracorporeal treatment is indicated "if Tl exposure is highly suspected on the basis of history or clinical features (2D)", and separately if the concentration exceeds 1.0 mg/L (4.9 µmol/L) (2D) "assuming Tl concentrations are readily available".¹ The guideline was written by people who knew the assay would not be to hand.
Do not give dimercaprol or penicillamine. "Strong evidence speaks against" both, and penicillamine "may cause redistribution of thallium into the central nervous system".² This is the reverse of every other page in this band, and a metal-poisoning reflex will produce the wrong drug here.
Do not load with potassium to force a diuresis. It "appears harmful".² The mechanism makes it sound compelling, which is exactly why it needs stating explicitly.
Activated charcoal is a defensible holding measure. Its use, "single- or multiple-dose", is "supported by in vitro binding experiments and some animal data", and charcoal haemoperfusion "may be a useful adjunct".²
Falling concentrations do not mean a recovering nerve.⁴ Follow the neurology, and expect to be arranging long-term follow-up rather than discharging on a normalised level.
Think about the household and the source. Thallium salts have been used as rodenticides and in manufacturing,² and a poisoning is far more likely to be deliberate or occupational than accidental. Suspected deliberate poisoning is a police matter as well as a clinical one.

The antidote, from the poison's side

Thallium is the only page in this band where the correct treatment is an oral binder rather than a chelator, and the only one where extracorporeal removal has a published recommendation. Both follow from kinetics rather than from chemistry: the poison recycles through the gut, and it clears slowly enough that removing it is worth attempting.

The EXTRIP recommendations for thallium, with their grades¹

General"ECTR is recommended in severe Tl poisoning (1D)"

Indication — clinical"If Tl exposure is highly suspected on the basis of history or clinical features (2D)"

Indication — concentration"Assuming Tl concentrations are readily available, if Tl concentration is >1.0 mg/L (4.9 µmol/L) (2D)"

Timing"ECTR should be initiated as soon as possible, ideally within 24–48 hr of Tl exposure (1D)"

CessationSuggested "until Tl serum concentration is 0.1 mg/L (0.5 µmol/L) for a minimal duration of 72 hr (2D)"

Modality"Intermittent hemodialysis is the preferred initial ECTR, especially after an acute Tl ingestion (1D)"; "Intermittent hemoperfusion or continuous renal replacement modalities" are "valid alternatives if intermittent hemodialysis is not available (1D)"

Reading the grades, which are the most informative part of the guidance

Every recommendation above is graded D — the lowest quality of evidence in the system EXTRIP uses. Four of the seven graded statements are nonetheless graded 1, meaning strong (the modality row carries two separately graded clauses). That combination is worth understanding rather than glossing: a strong recommendation on very low quality evidence is what a panel produces when the intervention is plausible, the alternative is a poisoning with lasting neurological sequelae, and no trial exists or is ever likely to. Compare lithium, where the recommendation to dialyse rests on level of evidence A while every recommendation about when is graded D. Thallium has no A anywhere. The certainty in this guideline is entirely about direction and not at all about evidence.

Prussian blue — a lattice, not a drug: It is an ion-exchange compound given orally that binds thallium in the gut lumen, interrupting the enterohepatic and enteroenteric recycling that would otherwise return it to the circulation. It is not absorbed and does not act on the patient. Hoffman's assessment is that "multiple animal studies give evidence for enhanced elimination and improved survival with Prussian blue", and that "Prussian blue's safety profile is superior to that of other proposed therapies and it should be considered the drug of choice in acute thallium poisoning".²
Why 'drug of choice' is a claim about safety here: The same paragraph also states: "Unfortunately, despite the fact that many humans have been treated with Prussian blue, the data presented are insufficient to comment definitively on its efficacy."² Traditional teaching The recommendation is explicitly a judgement about the balance of risk, not a finding of demonstrated benefit — animal evidence for efficacy, human evidence only for safety. This is a treatment-efficacy downgrade under this library's stated exemption, the same move as the glucagon badge on the beta-blocker page.
A second, unresolved question about the same drug: There are two forms of Prussian blue and the evidence does not line up with the product. A review of the English-language literature found that "the majority of data supporting the efficacy of Prussian blue in thallium poisoning involves the use of the soluble form", while the form approved for clinical use is the insoluble one — for which "there is a paucity of analogous data" in thallium.³ The authors' conclusion is the honest one: "Whether the physicochemical differences between soluble and insoluble Prussian blue have any effect on outcomes in human poisoning is not known."³ The best-supported antidote in this poisoning may not be the formulation that was studied, and nobody currently knows whether it matters.
Why the chelators are contraindicated rather than merely useless: "Strong evidence speaks against the use of traditional metal chelators such as dimercaprol (British Anti-Lewisite) and penicillamine, and the latter may cause redistribution of thallium into the central nervous system."² Redistribution is the specific hazard, and it is the same hazard that makes dimercaprol second-choice on the arsenic and mercury pages, where the water-soluble analogues are preferred because they "do not redistribute arsenic or mercury to the brain". Here the concern is not a relative disadvantage but a reason not to give the drug.

Critical appraisal

Two evidence-tier downgrades appear on this page. The first is on the mechanism of toxicity, and its citation for the doubt is a direct statement rather than an absence: "the exact mechanism of toxicity has not been established", in the same sentence that lists the candidate mechanisms.² The second is on the efficacy of Prussian blue, where the same review states that the human "data presented are insufficient to comment definitively on its efficacy"² while recommending it on safety grounds — a treatment-efficacy downgrade under this library's stated exemption.
A deliberate non-downgrade: the potassium-mimicry entry mechanism is badged established. Hoffman states it without hedging, in contrast to the same paragraph's explicit hedge about the mechanism of toxicity.² The source distinguishes what it is sure of from what it is not, and this page preserves that distinction rather than flattening the whole account to one tier. An auditor should test whether that separation is justified, because it is the most consequential editorial judgement on the page.
The contraindication of dimercaprol and penicillamine is presented as a finding, not as a badge, because it is a positive statement of evidence against a treatment rather than a downgrade of a mechanism. "Strong evidence speaks against" is the source's own characterisation.² It would be a category error to badge it, and it is noted here because it is the kind of claim that invites one.
The half-life of 3.8 to 5.7 days is from five treated patients and is stated as such.⁴ It is elimination under therapy, not natural clearance, and it should not be read as a property of the poison alone. The one-year electrophysiological findings come from the same five patients.
No timing figure is given for the onset of alopecia, because none of the sources used here supplies one. What is stated is the ordering — "sensory symptoms generally preceded the onset of alopecia"⁴ — which is what the sources support and what the clinical point actually requires. This is deliberate: writing a plausible interval that no source states is the failure that produced a Band D correction, and the temptation here was real, because a specific number would have read more authoritatively.
EXTRIP's cessation recommendation is quoted with its slightly awkward original wording. The published text reads "is suggested until Tl serum concentration is 0.1 mg/L (0.5 µmol/L) for a minimal duration of 72 hr (2D)".¹ It has not been silently smoothed into more fluent English, because paraphrasing a threshold is how thresholds change meaning.
Both units are given for both EXTRIP concentrations — 1.0 mg/L (4.9 µmol/L) and 0.1 mg/L (0.5 µmol/L)¹ — because unit stripping has recurred across three bands of this library and metals are the most unit-dense band so far.
No lethal dose, lethal concentration or comparative-lethality framing appears on this page. Thallium attracts exactly that kind of writing, and it is out of scope here. The page also declines to describe anything about the acquisition or use of thallium salts beyond noting that access to them is a public-health concern the review itself raises.²

How this page connects to the rest of the library

Thallium is the band's counter-example and it was placed last for that reason. It shares the band's central pattern — molecular mistaken identity — with lead and arsenic, and takes it furthest, since potassium's machinery is universal. It shares its latent phase with arsenic, both being tissues declaring on their own clock. But it inverts the band's therapeutics: the dithiol chelators that are the treatment on arsenic and mercury are contraindicated here,² and the dialysis that is futile on every other page in the band is recommended.¹ Its closest relative outside the band is lithium — the library's other genuinely dialysable ion with no metabolism and no antidote in the usual sense — and the comparison between lithium's level-of-evidence A and thallium's uniform D is the clearest illustration in the library of how differently two EXTRIP recommendations can be supported.

Evidence tier of the mechanisms on this pageEstablishedDemonstrated in humans, or in a model that reproduces the human syndromeInferredConsistent with the biochemistry and widely accepted, but the causal step has not been shown in humansTraditional teachingTaught and repeated but not demonstrated — the source questioning it is cited

References

1
EXTRIP Workgroup. Thallium — recommendations. extrip-workgroup.org/thallium. The full recommendation set with grades, including the cessation criteria that the journal abstracts omit: general recommendation, two indications, timing, cessation and modality. Parsed in full 7 September 2026. Thallium is one of 22 substances the workgroup has addressed and the only member of this band among them.
2
Hoffman RS. Thallium toxicity and the role of Prussian blue in therapy. Toxicological Reviews 2003;22(1):29–40. PMID 14579545. The backbone of this page: potassium-mimicry entry, the explicit statement that the mechanism of toxicity has not been established, the neuropathy-and-alopecia syndrome, the atypical gastrointestinal picture, the evidence against dimercaprol and penicillamine, the harm of forced potassium diuresis, and the assessment of Prussian blue as drug of choice on safety with human efficacy data insufficient.
3
Thompson DF, Callen ED. Soluble or insoluble prussian blue for radiocesium and thallium poisoning? The Annals of Pharmacotherapy 2004;38(9):1509–14. PMID 15252192. Search of MEDLINE, Toxline and EMBASE to August 2003. The thallium evidence is predominantly for the soluble form while the approved product is insoluble, and whether the difference affects human outcomes is not known.
4
Chen C, Yuan Y, Tan W, et al. Acute thallium poisoning: clinical features, toxicokinetics and one-year neurological outcomes. Clinical Toxicology 2026;64(9):832–5. PMID 42572989. Five patients with confirmed acute poisoning, followed for one year. Serum half-life 3.8–5.7 days by nonlinear regression under treatment; sensory symptoms generally preceded alopecia; distal axonal neuropathy with reduced compound muscle action potential amplitudes; residual axonal involvement persisting at one year in some.
5
National Poisons Information Service. TOXBASE — NPIS 0344 892 0111. The authoritative UK source for thallium risk assessment, Prussian blue supply and management. Login-gated, and deliberately not quoted anywhere on this page.

Last reviewed 2026-09-08 · Author: Dr Nirmalya Hore

Thallium

At a glance