Why this poison is interesting

Aconite completes a triptych. Yew blocks the cardiac sodium channel; local anaesthetics and the drugs on the sodium-channel-blockade page block it too. Aconitine does the exact opposite — it binds the channel and prevents it from inactivating, so instead of failing to open, the channel fails to close. A channel that will not close fires repetitively, and the tissues that depend on crisp, self-terminating action potentials — nerve and myocardium — misbehave in a characteristic way.

That inversion is the whole interest of the page, and it has a practical payoff. Because the poison acts on peripheral sensory nerves as readily as on the heart, the earliest sign is not cardiac at all: it is paraesthesia — a numb, tingling mouth and face, then limbs — appearing before the arrhythmia. A poison that warns you in the lips before it reaches the ventricle is unusual, and recognising the sequence is the difference between anticipating the cardiac phase and being surprised by it.

The toxic principle

Aconitine is a site 2 neurotoxin. Voltage-gated sodium channels have several distinct binding regions for toxins; site 2 is where the batrachotoxin-like agents act, and binding there shifts the channel towards the open state and prevents inactivation.¹ Normally a sodium channel opens for a fraction of a millisecond and then inactivates, ending the upstroke of the action potential. With aconitine bound, that closing step fails: the channel stays open, sodium continues to enter, and the membrane cannot reset cleanly.

The signature cardiac rhythm is ventricular tachyarrhythmia, including bidirectional ventricular tachycardia — the beat-to-beat alternating axis otherwise most associated with digoxin.¹ Its appearance here, in a patient with a tingling face and no reason to be on digoxin, is a strong pointer to aconite. The neurological effects run in parallel: paraesthesia and numbness from sensory nerve involvement, then weakness, and in severe poisoning a mixed picture of autonomic and central features.

Toxicokinetics

Aconitine is rapidly absorbed across mucosa and skin, which is why symptoms can begin within minutes of ingestion and why handling the plant matters. As with yew, there is no licensed product and no formal human pharmacokinetic dataset, so the table is honest about its gaps.

Aconitine — a fast poison with a thin kinetic record
Parameter	Therapeutic	In overdose	Why it changes
Absorption	Rapid across gastrointestinal mucosa and skin; onset of paraesthesia within minutes to about an hour¹	A larger ingestion simply reaches the arrhythmic threshold sooner	The speed is the clinically dominant feature: there is little decontamination window, and a patient can move from tingling lips to ventricular arrhythmia within the first hour or two.
Distribution	Lipophilic alkaloid; crosses membranes and the blood–brain barrier freely	Not quantified in humans	CNS penetration is why central as well as peripheral neurological features occur.
Metabolism / elimination	Hepatic metabolism and renal excretion of aconitine and metabolites are described; elimination is not precisely characterised in overdose	Not usefully quantified for real-time care	There is no level to titrate; the duration of danger is judged from the rhythm.
Dialysability	—	No established role. No pharmacokinetic basis for extracorporeal removal	As with yew, the extracorporeal intervention that has rescued refractory cases is mechanical circulatory support, sustaining the heart through the arrhythmic period, not toxin clearance. Inferred

Metabolism and the metabolites

Aconitine is active as ingested — there is no bioactivation step to wait through, so the poisoning has no latent phase in the amatoxin sense. Interestingly, the traditional processing of medicinal aconite works in the opposite direction to a bioactivation story: boiling and soaking hydrolyse aconitine to less toxic derivatives, which is precisely why inadequately processed herbal aconite causes poisoning. Metabolism, in other words, is mostly a detoxifying step here, and the danger is when it has not happened.

Aconitine — processing detoxifies; the danger is when it is skipped

Aconitine (root / foliage / unprocessed herbal aconite)Already the toxic species. Site 2 sodium-channel activator¹
Traditional processing — prolonged boiling / soaking (hydrolysis)Converts aconitine to less toxic benzoylaconines and aconines — a detoxifying step, not an activating one
Persistent sodium currentChannels that cannot inactivate → re-excitation, ectopy, ventricular arrhythmia and paraesthesia

Elimination and accumulation

Aconite poisoning is an acute single-exposure event, so there is no chronic accumulation story of the digoxin kind. What matters clinically is that the arrhythmic phase can persist for hours and can recur, so a patient who has reverted is not necessarily finished, and the monitoring period must outlast the first arrhythmia rather than end with it. Because there is no measurable falling concentration, the decision about when a patient is safe is a rhythm-and-time judgement made with NPIS, not a toxicokinetic one.

Target organs — and why those

Aconitine acts wherever voltage-gated sodium channels carry the load, which is nerve and muscle. The heart is the lethal organ; the peripheral nerves are the informative one.

Myocardium and conducting system

TargetCardiac voltage-gated sodium channels held open at site 2

Why hereA channel that cannot inactivate leaves the myocyte prone to premature depolarisations and re-excitation, generating ventricular ectopy and tachyarrhythmia rather than the bradycardic, wide-QRS picture of channel blockade. Bidirectional VT is the near-signature. Established

At the bedsideVentricular arrhythmia is the cause of death; it is frequently refractory to standard antiarrhythmic drugs and may require mechanical circulatory support.¹

Peripheral sensory nerves

TargetNeuronal sodium channels in sensory afferents

Why hereSensory neurons are exquisitely sensitive to a persistent sodium current, which is why the poisoning declares itself first as paraesthesia — a numb, tingling mouth, face and limbs — before the cardiac phase. This early, distinctive symptom is the mechanism's gift to diagnosis. Established

At the bedsidePerioral and limb paraesthesia and numbness are typically the first symptoms, often within minutes to an hour of ingestion.¹

Central nervous system and autonomic control

TargetCentral sodium channels; the alkaloid crosses the blood–brain barrier

Why hereCNS penetration produces central features — dizziness, agitation, reduced consciousness — and autonomic disturbance including hypotension and salivation, layered onto the peripheral and cardiac effects. Inferred

At the bedsideCentral and autonomic features accompany the cardiac and sensory picture but do not usually dominate it.

Timeline of effects

Aconite ingestion — the mouth warns before the heart

Time

What you seeWhat is happening

Minutes–1 hParaesthesia
What you seeNumbness and tingling of the mouth, face and limbs; nausea, vomiting; sometimes weakness.
What is happeningRapidly absorbed aconitine binds sensory neuronal sodium channels; the persistent current is felt as tingling and numbness before the heart is visibly affected.
HoursCardiac phase
What you seeVentricular ectopy, ventricular tachycardia including bidirectional VT, hypotension; potentially cardiac arrest.
What is happeningCardiac sodium channels held open produce re-excitation and ventricular arrhythmia; the rhythm is often refractory to standard drugs.
Prolonged / recurrentPersistence
What you seeArrhythmia may persist for hours or recur after apparent control.
What is happeningUntil the alkaloid clears, the substrate for arrhythmia remains; the reported survivals from refractory arrest involve mechanical support bridging this period.

What the mechanism predicts at the bedside

Paraesthesia plus a ventricular arrhythmia, without a cardiac drug history, should raise aconite. The perioral and limb tingling is the mechanism showing itself in sensory nerves before the heart, and it is the most useful single clue.¹
Bidirectional VT here is not digoxin. The same rhythm has two very different causes; in a patient with paraesthesia and a plausible plant or herbal exposure, aconitine — not a glycoside — is the likely source, and digoxin-specific Fab has no role.¹
Bicarbonate is not the reflex. Unlike yew and the sodium-channel-blockade drugs, the lesion is channel opening, not blockade, so there is no widened-QRS-from-blockade to alkalinise away; the arrhythmia is managed on its own terms with NPIS advice.
Expect refractoriness and think early about escalation. Aconite ventricular arrhythmia is often resistant to first-line drugs; amiodarone and flecainide are reported, and mechanical circulatory support has bridged refractory cases. Early NPIS discussion and critical-care involvement matter.¹
There is no level and little decontamination window. Onset is fast, so management is supportive and rhythm-directed from the outset.

The antidote, from the poison's side

Aconite has no specific antidote, and the reason is the same structural one as yew: there is no receptor to competitively occupy with a drug already in the cupboard, no depleted cofactor to replace, and no antibody raised against the alkaloid. The management is to keep a poisoned heart alive until the toxin clears.

So aconite sits with yew as the band's two antidote-less cardiotoxins, distinct from the glycoside plants that have a specific binder. The mechanistic lesson is worth stating plainly: a poison that acts on an ion channel by a subtle kinetic change — holding it open, or shutting it — is far harder to antidote than one that binds a discrete target a drug can compete for.

Critical appraisal

The site-2 sodium-channel mechanism is established; the precise translation to each clinical feature is partly inferred. That aconitine binds neurotoxin site 2 and prevents channel inactivation is demonstrated pharmacology; attributing each specific arrhythmia and neurological sign to that single action is well supported but, for some features, an extension of it.¹ Established
The antiarrhythmic recommendations are case-report grade. Amiodarone and flecainide appear in the literature as agents that have been used, sometimes successfully; there is no controlled comparison, and the optimal drug for aconite-induced ventricular arrhythmia is genuinely unsettled.¹ Inferred
Processing chemistry is established but variable in practice. Hydrolysis of aconitine to less toxic derivatives by boiling and soaking is well characterised; the residual toxicity of a given herbal preparation depends on how it was processed and cannot be assumed from the fact that it was processed at all. Established
Severity and outcome data are limited. Aconite poisoning is uncommon in the UK and most published experience is from regions where medicinal aconite is used, so quantitative estimates of severity and mortality should be read as indicative rather than precise.

References

1
Chan TYK. Aconite poisoning. Clinical Toxicology (Philadelphia) 2009;47(4):279–85. PMID 19514874.

Aconite (aconitine)

At a glance