Strychnine is an alkaloid derived from dried seeds of the Strychnos nux-vomica tree.1 The tree is native to India, Northern Australia and the East Indies.2 Strychnine is a potent poison which can cause serious adverse health effects, including death. It is a white, odourless powder that can be inhaled, ingested or injected. Historically, strychnine was used as a rodenticide (a chemical used to kill rodents), but its use has been banned or restricted in most countries because it is highly toxic to both humans and animals. In the past, it was also used to treat many human ailments, and in the 1980s, it was still found in many over-the-counter medications in the United States, such as cold remedies, digestive aids, sedatives and stimulants.2 Strychnine is still sometimes used in traditional and homoeopathic medicines and has also been used as a performance-enhancing drug in sports, as low doses are thought to have performance-enhancing qualities.2
Today, strychnine poisoning usually occurs due to intentional ingestion as a means of suicide or homicide. It may also occur due to accidental ingestion or injection as it is sometimes mixed in with other street drugs such as LSD, heroin and cocaine.2 In the United States, strychnine is still used as an outdoor pesticide, and the American Association of Poison Control Centers' annual report detailed 72 poisonings and one death from strychnine poisoning in 2015.2
Strychnine: chemical properties and mechanism of action
Strychnine has been reported to be lethal at doses between 50 and 100mg.3 It is metabolised mainly in the liver and partially excreted by the kidneys.2 Complications of strychnine poisoning include hyperthermia, renal failure and rhabdomyolysis, and the cause of death is usually due to respiratory failure.3
Strychnine is a competitive inhibitor of postsynaptic glycine receptors, meaning it binds to the receptors and prevents the binding of glycine, stopping the receptor from performing its function. Postsynaptic glycine receptors are found in the central nervous system and are a strong blocker of different types of muscle and neuronal nicotinic acetylcholine receptors.2,3 Glycine is an important inhibitory neurotransmitter in the spinal cord and brain stem. This means it blocks or prevents a chemical message from being passed further along. Therefore, preventing glycine binding leads to the uncontrolled stimulation of postsynaptic neurons, which in turn leads to involuntary muscle contractions.2 Patients first exhibit severe painful muscle spasms without their mental state or consciousness being affected. However, continuous and uncontrolled muscle contractions can lead to hyperthermia, acidosis and eventually asphyxia (suffocation).2
Symptoms appear within 15-60 minutes after ingestion of strychnine but appear much faster when taken intranasally or intravenously. Without treatment, strychnine poisoning can cause death within several hours.2
Symptoms of strychnine poisoning
A person exposed to low or moderate doses of strychnine by any route will likely show the following symptoms:
- Apprehension or Anxiety4
- A heightened sense of awareness (hearing, visual and tactile sensations)1
- Painful muscle spasms, possibly leading to hyperthermia, liver or kidney injury1
- Uncontrollable aching or pain in the neck, back or chest4
- Stiffness in the arms, face and legs2
- Jaw tightness2
- Muscle pain and soreness
- Difficulty breathing
- Dark urine
- Initial consciousness and awareness of symptoms
Someone exposed to high doses of strychnine may suffer from respiratory failure and/or
Brain death within 15 to 30 minutes of exposure
When diagnosing strychnine poisoning, a differential diagnosis must be made to ensure correct treatment; this means other conditions with similar presentation must first be ruled out.1,2 Common conditions considered during differential diagnosis include:
- Phenothiazine overdose2
- Cocaine and phencyclidine use2
- Exposure to chemicals that may cause myoclonus or seizures, such as chlorinated hydrocarbons, isoniazid, cyanides, organophosphates2
- Conversion disorder1
- Hemorrhagic stroke1
- Jaw dislocation1
- Neuroleptic malignant syndrome1
- Tardive dystonia1
Diagnosis and medical evaluation
If a patient is suffering from symptoms of strychnine poisoning, a detailed medical history should be taken. If the patient has reported recent ingestion of herbal medicines or prior recreational drug use, especially cocaine or heroin, then this could increase the likelihood of strychnine poisoning.2
A healthcare provider will perform a physical exam and make sure the airways are secured if there is respiratory distress. The patient’s temperature should also be assessed to check for hyperthermia.2
To test for strychnine poisoning, thin-layer chromatography can be performed on gastric aspirate and urine samples.2 Further tests carried out should include arterial or venous blood gas tests, a lactate test, urinalysis and a basic metabolic panel (BMP) blood test.2
If you suspect that you or a person you know is suffering from strychnine poisoning, you should immediately contact emergency medical services. Below is some emergency care advice in case of strychnine exposure:
- In case of ingestion, fluids should not be given, and vomiting should not be induced.
- If exposure is via the air, it is best to move away from the area.
- If exposure to strychnine was via the skin, remove any contaminated clothing and wash the contaminated area with soap and water.
- In case of contact with the eyes, remove any contact and rinse the eyes with clean water for 10 to 15 minutes.
Once a patient has been admitted to the hospital, treatment is mainly supportive, with the airway first being secured and endotracheal intubation used if necessary. Gastrointestinal decontamination (methods to evacuate the stomach of any poisons) may be used in the first few hours after ingestion of strychnine. Supportive care includes the administration of intravenous fluids for hydration, barbiturates and benzodiazepines to control convulsions and muscle spasms, and cooling measures for hyperthermia.2 Hyperthermia should be treated aggressively by ice-water immersion, using a cooling blanket or cool mist depending on the level of temperature elevation; in severe cases, dantrolene should be used.1
If the convulsions and muscle spasms can’t be controlled, the patient should be sedated and immobilised, usually with neuromuscular blockers such as pancuronium or vecuronium bromide, and then ventilated.1 Following only minor or moderate exposure to strychnine, the patient will usually make a full recovery with no neurological or physical consequences. However, in more severe cases, long-term effects may result from damage caused by the poisoning, such as kidney damage or brain damage caused by low oxygen levels.
Strychnine is a strong poison which can cause severe damage to the body and death if not treated appropriately. In the past, before the consequences were known, strychnine was used to treat various ailments in humans and as a rodenticide. In the present day, due to its severe toxicity, its use has been restricted or banned in most countries. However, exposure may still occur due to its continued use as a pesticide in some countries and also in herbal or homoeopathic medicine. Recreational drug users are also at risk of strychnine poisoning as it is sometimes used to “cut” illegal drugs such as cocaine or heroin.
Symptoms of strychnine poisoning include severe, uncontrolled muscle contractions, hyperthermia and respiratory distress. Medical treatment is mainly supportive, including the administration of drugs to control convulsions and hyperthermia and ventilating the patient if needed. Recovery without any long-term effects is possible with quick medical treatment, and rapid intervention is key to saving a patient’s life.
- Imaj | the israel medicine association journal | volume 10, number 2, february 2008 | strychnine - a killer from the past [Internet]. [cited 2023 Sep 1]. Available from: https://www.ima.org.il/MedicineIMAJ/viewarticle.aspx?year=2008&month=02&page=142
- Otter J, D’Orazio JL. Strychnine toxicity. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Sep 1]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK459306/
- Chen J, Qu Y, Wang D, Peng P, Cai H, Gao Y, et al. Pharmacological evaluation of total alkaloids from nux vomica: effect of reducing strychnine contents. Molecules [Internet]. 2014 Apr 10 [cited 2023 Sep 1];19(4):4395–408. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6270886/
- ‘Nux Vomica’. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, National Institute of Diabetes and Digestive and Kidney Diseases, 2012. PubMed, Available from: http://www.ncbi.nlm.nih.gov/books/NBK589896/.