Strychnine poisoning can be fatal to humans and other animals and can occur by inhalation, swallowing or absorption through eyes or mouth. It produces some of the most dramatic and painful symptoms of any known toxic reaction, making it quite noticeable and a common choice for assassinations and poison attacks. For this reason, strychnine poisoning is often portrayed in literature and film, such as the murder mysteries written by Agatha Christie.
The probable lethal oral dose in humans is 1.5 to 2 mg/kg. Similarly, the median lethal dose for dogs, cats, and rats ranges from 0.5 to 2.35 mg/kg.
Presentation in humans
Ten to twenty minutes after exposure, the body's muscles begin to spasm, starting with the head and neck in the form of trismus and risus sardonicus. The spasms then spread to every muscle in the body, with nearly continuous convulsions, and get worse at the slightest stimulus. The convulsions progress, increasing in intensity and frequency until the backbone arches continually. Convulsions lead to lactic acidosis, hyperthermia and rhabdomyolysis. These are followed by postictal depression. Death comes from asphyxiation caused by paralysis of the neural pathways that control breathing, or by exhaustion from the convulsions. The subject usually dies within 2–3 hours after exposure.
One medical student in 1896 described the experience in a letter to the Lancet:
Three years ago I was reading for an examination, and feeling "run down". I took 10 minims of strychnia solution (B.P.) with the same quantity of dilute phosphoric acid well diluted twice a day. On the second day of taking it, towards the evening, I felt a tightness in the "facial muscles " and a peculiar metallic taste in the mouth. There was great uneasiness and restlessness, and I felt a desire to walk about and do something rather than sit still and read. I lay on the bed and the calf muscles began to stiffen and jerk. My toes drew up under my feet, and as I moved or turned my head flashes of light kept darting across my eyes. I then knew something serious was developing, so I crawled off the bed and scrambled to a case in my room and got out (fortunately) the bromide of potassium and the chloral. I had no confidence or courage to weigh them, so I guessed the quantity-about 30 gr. 30 grains, about 2 grams bromide of potassium and 10 gr. chloral-put them in a tumbler with some water, and drank it off. My whole body was in a cold sweat, with anginous attacks in the precordial region, and a feeling of "going off." I did not call for medical aid, as I thought that the symptoms were declining. I felt better, but my lower limbs were as cold as ice, and the calf muscles kept tense and were jerking. There was no opisthotonos, only a slight stiffness at the back of the neck. Half an hour later, as I could judge, I took the same quantity of bromide, potassium and chloral– and a little time after I lost consciousness and fell into a " profound sleep," awaking in the morning with no unpleasant symptoms, no headache, &c., but a desire " to be on the move " and a slight feeling of stiffness in the jaw. These worked off during the day.
Treatment
There is no specific antidote for strychnine. "The convulsions are often triggered by stimuli – when your body senses something, neurons want to fire, and if they aren’t controlled seizures occur – so patients are generally kept in quiet, dark rooms." Treatment of strychnine poisoning involves an oral application of an activated charcoal infusion which serves to absorb any poison within the digestive tract that has not yet been absorbed into the blood. Anticonvulsants such as phenobarbital or diazepam are administered to control convulsions, along with muscle relaxants such as dantrolene to combat muscle rigidity. If the patient survives past 24 hours, recovery is probable.
The treatment for strychnine poisoning in the late 19th and early 20th centuries was to administer tannic acid which precipitates the strychnine as an insoluble tannate salt, and then to anaesthetise the patient with chloroform until the effects of the strychnine had worn off.
Detection in biological specimens
Strychnine is easily quantitated in body fluids and tissues using instrumental methods in order to confirm a diagnosis of poisoning in hospitalized victims or to assist in the forensic investigation of a case of fatal overdosage. The concentrations in blood or urine of those with symptoms are often in the 1–30 mg/L range.