Continuing Education Activity

Strychnine poisoning is a rare but life-threatening toxicologic emergency characterized by rapid neuromuscular deterioration. Historically used as a medicinal tonic, strychnine is now encountered primarily in intentional ingestions, contamination of illicit substances, and exposure to rodenticides or certain herbal preparations. Risk factors include access to commercial or agricultural products containing strychnine, substance use, and self-harm behavior. Strychnine acts as a competitive antagonist at postsynaptic glycine receptor sites within the spinal cord and brainstem, eliminating inhibitory modulation and producing unchecked reflex excitability. Minimal sensory stimuli may precipitate generalized, painful muscle spasms with preserved consciousness.

Clinical manifestations may include stimulus-induced rigidity, opisthotonos, hyperthermia, rhabdomyolysis, metabolic acidosis, or potential progression to respiratory failure. Diagnosis is primarily clinical, based on characteristic episodic spasms with intact awareness and relevant exposure history. Toxicologic confirmation may support but does not exclude the diagnosis. Management requires immediate supportive care, strict reduction of external stimuli, airway protection, parenteral benzodiazepine administration, and, in refractory cases, neuromuscular blockade with mechanical ventilation. Prognosis is favorable with timely intervention, although delayed treatment may result in hypoxic injury or death.

This activity for healthcare professionals is designed to enhance the learner's competence when evaluating and managing strychnine toxicity. Participants strengthen their mastery of the condition's etiology, risk factors, pathophysiology, clinical presentation, and evidence-based diagnostic and therapeutic approaches. Greater proficiency supports interprofessional collaboration to optimize care for affected individuals.

Objectives:

• Identify the clinical manifestations of strychnine toxicity to establish patient risk and prioritize urgent interventions.
• Implement best practices for managing strychnine toxicity, including prompt stabilization, airway protection, muscle-spasm control, and prevention of secondary complications.
• Differentiate strychnine toxicity from similar toxidromes, such as tetanus, neuroleptic malignant syndrome, and stimulant-induced seizures, based on clinical and diagnostic findings.
• Collaborate with all members of the interprofessional team, including specialists such as toxicologists, emergency medicine physicians, and intensivists, to provide efficient, comprehensive, and coordinated care for individuals experiencing strychnine poisoning.

Introduction

Strychnine is a highly toxic alkaloid derived from the Strychnos nux-vomica plant, which grows in Sri Lanka, India, and Australia.[1] Historically, strychnine was used in rodenticides, pesticides, and traditional medicine preparations.[2] Although regulatory restrictions have limited the use of this agent due to severe neurotoxicity, exposures continue to occur, primarily via ingestion and dermal routes.[3][4]

Strychnine acts as a competitive antagonist at postsynaptic glycine receptors in the spinal cord, producing unopposed motor neuron excitation.[5] The hallmark of toxicity consists of awake seizures—episodic, involuntary, and painful skeletal muscle contractions with preserved consciousness and an absence of a postictal period.[6] Intact consciousness during spasms differentiates the condition from true epileptic seizures. The absence of tonic muscle contraction between episodes distinguishes strychnine poisoning from tetanus, which presents with continuous muscle rigidity.[7]

Complications from prolonged muscle contractions include hyperthermia, metabolic acidosis, rhabdomyolysis leading to acute kidney injury and renal failure, and asphyxiation from sustained contraction of respiratory muscles.[8][9] Treatment primarily consists of supportive care, using benzodiazepines and other sedative-hypnotic agents to control muscle convulsions and seizures. Severe cases with refractory convulsions or respiratory compromise may require neuromuscular blockade and airway protection. With prompt recognition and management of complications, patients surviving acute poisoning generally have a favorable prognosis and do not develop chronic sequelae.[10][11]

Etiology

Strychnine poisoning occurs primarily through ingestion of naturally occurring compounds and commercial products. Cases are frequently associated with intentional use, including suicidal or homicidal ingestion. The most commonly reported sources include rodenticides and pesticides, such as gopher killer.[12] Although strychnine was banned as a rodenticide in the European Union in 2006 and in Canada in 2023, exposures continue from preexisting supplies. Unintentional poisoning has been reported following ingestion of traditional herbal remedies, including the Chinese preparation maqianzi—the dried ripe seed of Strychnos nux-vomica containing strychnine and brucine—and the Cambodian remedy known as slang nut.[13][14][15] Less common routes of exposure include intravenous injection and intranasal insufflation, particularly with adulterated heroin or cocaine.[16][17]

Epidemiology

Strychnine is present in the seeds of Strychnos nux-vomica, a plant native to Southeast Asia, India, and Australia. In Cambodia, slang nut seeds are processed and used as traditional herbal medicine for rheumatism, fevers, arthritis, and musculoskeletal injuries. In traditional Chinese medicine, maqianzi is used for its anti-inflammatory and analgesic properties. In the United States, strychnine has been incorporated into poisons, rodenticides, and performance-enhancing drugs, as low doses were historically believed to enhance athletic performance. Historical and recent examples include the 1904 Olympic marathon winner, who ingested strychnine during competition, and the 2016 Olympic weightlifting bronze medalist, who tested positive for the substance.[18]

In the United States, the use of strychnine has declined markedlyfollowing numerous poisoning incidents and fatalities. During the 1930s, it was ranked among the leading causes of fatal pediatric ingestions. Strychnine remainedavailable in over-the-counter digestive aids, sedatives, stimulants, and cold remedies as late as the 1980s. The US Food and Drug Administration mandated the removal of this alkaloid from food and medicines in 1962. Strychnine was banned as an indoor pesticide in 1989 but continues to be used in outdoor rodenticides, such as gopher bait. The American Association of Poison Control Centers reported 65 exposures with no deaths in 2022 and 6 deaths between 2011 and 2022.[19]

Pathophysiology

Strychnine is a highly toxic, white, odorless, bitter crystalline alkaloid derived from the seeds of Strychnos nux-vomica. Strychnine acts as a competitive antagonist of the primary inhibitory neurotransmitter glycine at postsynaptic receptors in the spinal cord and brainstem. Loss of glycinergic inhibition permits unopposed excitatory signaling, resulting in involuntary muscle contractions. Higher motor neuron centers remain unaffected, producing preserved consciousness during severe, painful contractions, commonly termed awake seizures. Mental status is maintained until late stages, when complications of uncontrolled muscle activity— including hyperthermia, metabolic acidosis, renal failure, and additional physiologic derangements—develop.

After ingestion, symptoms typically develop rapidly within 15 to 30 minutes, but onset may be faster following inhalation, intravenous administration, or exposure to a large dose. Initial manifestations include excitability and heightened awareness, followed by vomiting and skeletal muscle contractions. Convulsions typically last 30 seconds to 2 minutes and present as opisthotonic posturing, with the back arched, extremities extended, and jaws clenched.

Episodes are frequently triggered by trivial stimuli, such as minor emotional or minimal sensory input (eg, auditory or tactile stimuli). Facial muscle contractions may produce risus sardonicus, resulting in a fixed, stiff sardonic smile. Uncontrolled muscle activity can cause tachycardia, hypertension, hyperthermia (up to 109.4 °F or 43 °C), and airway compromise due to jaw and neck rigidity.[20] Later complications include rhabdomyolysis, hyperkalemia, lactic acidosis, metabolic acidosis, and acute kidney injury.

Early fatalities typically result from asphyxiation due to intense respiratory muscle contractions. Death may also occur from severe hyperthermia or rhabdomyolysis with renal failure. Without treatment, strychnine poisoning can be fatal within several hours.

Toxicokinetics

Strychnine is rapidly absorbed following ingestion or inhalation, producing transiently detectable blood levels that quickly distribute to tissues. Dermal exposure has been reported from an alkaline solution that converted strychnine salt to the free base, enhancing absorption efficiency. Metabolism occurs primarily in the liver, with partial renal excretion. Strychnine follows first-order kinetics, exhibiting an elimination half-life of 10 to 16 hours and a large volume of distribution of 13 L/kg.[Goldfrank's Toxicologic Emergencies, Eleventh Edition 2019]

The alkaloid's large volume of distribution renders hemodialysis unlikely to enhance elimination. The median lethal dose ranges from 1.5 to 2 mg/kg. Postmortem assays reveal the highest strychnine concentrations in the hepatobiliary system. Urine and gastric measurements provide the most reliable assessment of exposure, whereas blood serum levels remain unreliable.[21]

History and Physical

Suspicion of strychnine poisoning arises from the combination of a relevant exposure source, such as herbal remedies, intravenous drug use, performance-enhancing drugs, rodenticides, or pesticides, and seizure-like activity in an awake patient without a postictal phase. Exposure may be intentional, such as a suicidal attempt, or accidental, such as mistaken ingestion or improper herbal remedy preparation. Recent cocaine or heroin use can provide a historical clue, as these illicit drugs are occasionally adulterated with strychnine. Timing and dose of exposure should be determined to assess the potential benefit of gastrointestinal decontamination.

Symptom onset is rapid, typically occurring within 15 to 30 minutes after ingestion and sooner following inhalation or intravenous administration. Hallmark physical findings include generalized muscle convulsions with preserved consciousness and absence of a postictal state. Common examination features include tachycardia, hypertension, trismus, opisthotonus, risus sardonicus, abdominal cramping, and muscle spasms. Sustained respiratory muscle spasm may result in respiratory arrest. Rarely, anterior tibial compartment syndrome develops secondary to prolonged muscle activity and rhabdomyolysis.[22] Toxicity generally resolves within 24 hours. Adequate supportive care during the initial phase typically results in favorable outcomes.

Evaluation

Laboratory evaluation for suspected strychnine poisoning should focus on detecting hyperkalemia, acidosis, rhabdomyolysis, and renal failure. Strychnine is measurable in gastric fluid, urine, or serum using high-performance thin-layer chromatography, gas chromatography-mass spectrometry, or liquid chromatography-tandem mass spectrometry.[23][24][25] Specific blood levels are not clinically useful because results are not readily available and correlate poorly with the severity of toxicity. Additional laboratory studies include a complete metabolic panel to rule out derangements in potassium levels (eg hyperkalemia) and renal and hepatic function; arterial or venous blood gases and lactate to evaluate metabolic acidosis; and urinalysis to detect myoglobinuria.

Treatment / Management

Management of strychnine poisoning focuses on supportive care, with emphasis on rapid control of muscle hyperactivity to prevent metabolic and respiratory complications. Patients with significant poisoning should receive intensive care, ideally under guidance from a regional poison control center or medical toxicologist. Gastrointestinal decontamination with activated charcoal (1 g/kg) may be considered within the first few hours of ingestion. Following airway protection, orogastric lavage may be considered for patients who present early or have ingested a life-threatening dose. Caution is warranted during gastrointestinal decontamination, as physical manipulation may provoke seizures.[26]

Benzodiazepines are the preferred first-line medications for strychnine-induced muscular convulsions.[27] Diazepam, lorazepam, and midazolam exhibit similar efficacy. Propofol and barbiturates may serve as secondary agents. Severe, refractory convulsions may require paralysis with a nondepolarizing neuromuscular blocker.

Life-threatening hyperthermia should be managed aggressively using a cooling blanket, evaporative cooling, or ice-water immersion, depending on severity. Adequate fluid resuscitation to maintain urine output above 1 mL/kg/h may prevent acute kidney injury from rhabdomyolysis.[28]

The rapid tissue distribution of strychnine (Vd = 13 L/kg) renders extracorporeal elimination ineffective. Forced diuresis is not recommended.[29] Asymptomatic exposures should undergo a 12-hour observation period to rule out clinically significant poisoning.

Differential Diagnosis

Differentiating strychnine toxicity from other conditions can be challenging due to overlapping clinical features. Key alternative diagnoses to consider include the following:

• Tetanus
• Seizure
• Serotonin syndrome
• Neuroleptic malignant syndrome
• Malignant hyperthermia
• Pesticide poisoning
• Rodenticide poisoning
• Compartment syndrome
• Rhabdomyolysis
• Renal failure
• Meningitis
• Encephalitis
• Sympathomimetic toxicity
• Liver failure
• Intracranial hemorrhage
• Drug-induced seizures
• Salicylate toxicity

Importantly, early symptoms of strychnine poisoning are often nonspecific. Prompt intervention at this stage maximizes the chance of survival and limits the severity of subsequent toxicity.

Prognosis

The prognosis of strychnine poisoning is generally favorable when patients receive effective supportive care during the initial 6 hours of toxicity. Early, aggressive intervention within this period is critical for survival, and most patients achieve complete recovery without long-term complications.[30][31]

Complications

Metabolic and respiratory complications of strychnine poisoning result from uncontrolled muscle hyperactivity. Sustained respiratory muscle contractions may cause hypoventilation and hypoxia, progressing to respiratory failure. Cardiovascular collapse can occur secondary to profound metabolic acidosis induced by tissue hypoxia. Prolonged muscular hyperactivity may produce rhabdomyolysis, potentially leading to renal failure and electrolyte disturbances. Excessive contractions may also precipitate life-threatening hyperthermia and multiorgan failure. Additional complications include aspiration pneumonitis, anoxic brain injury, pancreatitis, neuromuscular weakness, myalgias, and anterior tibial compartment syndrome.[32][33][34]

Deterrence and Patient Education

Although uncommon today, strychnine poisoning remains a medical emergency marked by severe, painful, conscious muscle hyperactivity and potentially fatal complications, including respiratory failure, profound metabolic acidosis, and hyperthermia. The toxin, derived from Strychnos nux-vomica seeds, is most often encountered through intentional ingestion of the alkaloid or exposure to adulterated illicit drugs, particularly stimulants such as cocaine; contaminated herbal products; or rodenticides and pesticides.

Healthcare professionals play a critical role in preventing exposure by educating patients, families, and communities about the dangers of strychnine-containing substances. Clinicians should emphasize that strychnine has no legitimate role in modern medicine or performance enhancement, despite misinformation in traditional remedies or online sources. Patients should be advised to avoid unregulated herbal preparations, obtain supplements only from reputable sources, and handle rodenticides and pesticides with caution, ensuring secure storage and proper use according to manufacturer instructions.

Harm-reduction counseling is essential for individuals using illicit substances, as strychnine contamination of street drugs can cause sudden, severe poisoning. Encouraging substance testing when community resources are available and facilitating access to addiction treatment programs can help reduce risk. Patients should be educated to recognize early warning signs, including muscle stiffness, agitation, and hypersensitivity to sound or touch, and to seek immediate medical attention if these symptoms occur. Proactive education, community awareness, and coordinated interprofessional prevention efforts can substantially decrease morbidity and mortality associated with strychnine exposure.

Pearls and Other Issues

Strychnine poisoning is characterized by episodic, painful muscle contractions with preserved consciousness, commonly referred to as conscious seizures, and requires early, aggressive control of muscle hyperactivity. Benzodiazepine administration constitutes the first-line therapy for muscular hyperactivity. Refractory cases may necessitate the use of barbiturates or propofol, or neuromuscular paralysis with a nondepolarizing neuromuscular blocker. Strychnine has been detected as an adulterant in cocaine and heroin, appearing as a white powder added to illicit drugs. Inhalation, insufflation, or intravenous injection produces a rapid onset of toxicity. Strychnine poisoning should be considered in any patient presenting with opisthotonic posturing following illicit drug use.

Enhancing Healthcare Team Outcomes

Effective management of strychnine poisoning requires a collaborative approach among healthcare providers to ensure optimal patient-centered care and improved outcomes. Healthcare professionals, including neurologists, emergency medicine physicians, intensivists, medical toxicologists, pharmacists, and nurses, involved in the care of exposed individuals must possess the clinical skills and knowledge necessary to diagnose and manage strychnine poisoning and its complications. Early diagnosis and rapid cessation of muscular hyperactivity are critical to reducing morbidity and mortality.

Patient education regarding potential sources of exposure and early recognition of toxicity is essential to prevent adverse outcomes. Proficiency in gastrointestinal decontamination is also important and should be performed under the guidance of a medical toxicologist, as activated charcoal and orogastric lavage may improve outcomes in life-threatening ingestions. Consultation with poison control centers provides 24-hour access to medical toxicology expertise, supporting timely and evidence-based management decisions.

The primary ethical tension in strychnine poisoning arises from balancing aggressive lifesaving interventions with a patient's autonomy, particularly when decision-making capacity is retained between convulsions following a self-harm attempt. According to the American College of Medical Toxicology, clinicians may intervene without informed consent if a toxic exposure presents an immediate threat to life or risks serious harm. In cases of intentional strychnine ingestion, the treating clinician must assess the patient's decision-making capacity and act in the patient's best interests. Permitting self-destruction is not consistent with long-term well-being and should be avoided. Nevertheless, medical providers must respect the patient's treatment preferences to the maximum extent possible, in accordance with accepted standards of care.[35]

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Disclosure: Daniel Menza declares no relevant financial relationships with ineligible companies.

Disclosure: Vincent Lee declares no relevant financial relationships with ineligible companies.