Strychnine is a potent poison known for its rapid and severe effects. Its history includes medicinal attempts and widespread use as a pest control agent.
What is Strychnine?
Strychnine is a highly toxic, colorless, crystalline alkaloid primarily obtained from the seeds of the Strychnos nux-vomica tree, native to southern Asia and India. It possesses an exceptionally bitter taste but is odorless. Chemically, it is a monoterpenoid indole alkaloid with the molecular formula C₂₁H₂₂N₂O₂. French chemists Joseph Bienaimé Caventou and Pierre-Joseph Pelletier first isolated strychnine in 1818 from Saint-Ignatius’ beans.
Strychnine’s Historical Use
Strychnine gained prominence as a rodenticide and pest control agent, with its use dating back to 1540. In the United States, it was first registered as a pesticide in 1947, though used earlier for vertebrate animal control. Many countries, including those in the European Union, banned its use as a rodenticide in 2006.
In the U.S., the Environmental Protection Agency (EPA) has significantly restricted its use under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). All above-ground applications of strychnine were suspended in 1988 due to risks to non-target species. Currently, its use is primarily limited to below-ground applications for controlling pocket gophers on residential lawns, pastures, and agricultural lands.
How Strychnine Poisons
Strychnine acts as a neurotoxin, targeting the nervous system. It functions as a competitive antagonist of glycine receptors in the spinal cord and brainstem. Glycine is an inhibitory neurotransmitter that normally helps control muscle contractions by hyperpolarizing nerve cells. By blocking these inhibitory signals, strychnine causes uncontrolled excitation of motor neurons.
This leads to severe muscle spasms, convulsions, and characteristic arching of the back (opisthotonus). Symptoms can appear rapidly, often within 15 to 60 minutes after exposure. Death results from asphyxiation due to sustained spasms of the respiratory muscles.
Dangers to Non-Target Organisms
Strychnine’s toxicity presents risks to organisms beyond its intended targets. Humans, pets, and wildlife are vulnerable to poisoning through direct ingestion or secondary exposure. Animals like dogs, cats, and birds of prey can be poisoned by consuming bait or scavenging on poisoned rodents. The probable lethal oral dose in humans is estimated between 1.5 to 2 milligrams per kilogram of body weight.
Symptoms in non-target organisms mirror those in target pests, including muscle twitching, hyperexcitability, and convulsions triggered by minimal stimuli. There is no specific antidote for strychnine poisoning; treatment focuses on managing symptoms and providing supportive care. Rapid absorption and severe neurological signs mean such poisonings are often fatal without immediate medical intervention.
Current Rodent Control Approaches
Modern rodent control emphasizes methods safer for non-target species and the environment. Integrated Pest Management (IPM) strategies combine multiple approaches for effective, long-term control. This includes prevention through sanitation and exclusion, such as sealing entry points larger than six millimeters. Removing food and water sources and reducing harborage areas also helps deter rodent populations.
Physical controls like snap traps and live traps are widely used and effective. When chemical options are necessary, anticoagulant rodenticides are more commonly employed. These substances, such as warfarin and brodifacoum, work by interfering with the blood’s clotting ability, leading to internal bleeding.