In patients with strychnine poisoning, inducing vomiting is absolutely contraindicated because of the risk of aspiration and loss of airway control following rapid onset of muscle contractions. Gastric lavage should be considered on an individual basis after evaluating potential benefits and risks.3 When gastric lavage is thought to be indicated, it may be important to protect and secure the airway with an endotracheal tube before attempting lavage. Activated charcoal (AC) binds strychnine effectively at a ratio of approximately 1:1; 1 g of AC will bind 950 mg of strychnine.4,88 In animal models, pretreatment67 and posttreatment71 with AC increase the median lethal dose in 50% of test subjects (LD50) for strychnine. Clinical evidence of the effectiveness of AC for strychnine ingestion was first demonstrated in 1831, when Professor Touery survived the ingestion of a lethal dose of strychnine by using AC in a demonstration before the French Academy of Medicine.
Currently, there is no evidence to recommend the use of multiple-dose AC or whole-bowel irrigation for strychnine poisoning. Although forced diuresis was once suggested as an effective means of enhancing the elimination of strychnine,88 subsequent data failed to demonstrate an increase in clearance81 and it is therefore no longer recommended. Peritoneal dialysis, hemodialysis, and hemoperfusion have not been extensively studied. However, because strychnine is rapidly distributed to the tissues93 with a large volume of distribution (13 L/kg), extracorporeal drug elimination procedures are unlikely to be useful and therefore not justified given their risks.
Supportive treatment remains the most important aspect of management in the majority of cases. The focus of care is to stop the muscular hyperactivity as soon as possible to prevent the metabolic and respiratory complications. At all times, unnecessary stimuli and manipulation of the patient should be avoided, as these activities trigger muscle contractions. Benzodiazepines remain the first line treatment for strychnine induced muscular hyperactivity.83,95 Although much of the evidence concerning the efficacy of benzodiazepines is based on clinical experience with diazepam,38,46,64 any of the other commonly used benzodiazepines (midazolam or lorazepam) would likely have similar effects. The initial dose of the benzodiazepine chosen should be the standard dose used for other indications, although doses of more than 1 mg/kg diazepam or its equivalent may be needed.41,56 In case of failed intravenous access, lorazepam or midazolam can be given intramuscularly or intraosseously. Dosing should be repeated until the patient demonstrates muscle relaxation and the contractions cease. In addition to benzodiazepines, barbiturates and propofol are also effective, although considered secondary therapies, in stopping the strychnine-induced hyperactivity.37,51,74,87 Benzodiazepines and barbiturates both work through agonism of γ-aminobutyric acid (GABA) receptor chloride complexes to increase the inhibitory neurotransmission to the spinal cord from the brain, and thus raise the reflex arc threshold.79 If these measures fail to control the muscular hyperactivity, a nondepolarizing neuromuscular blocker (NMB) should be administered. Only nondepolarizing NMBs should be used, as succinylcholine itself, a depolarizing NMB, induces muscle contractions.13,26,51,64,81 It is important to remember that strychnine has no direct effects on consciousness, so that sedation must always accompany neuromuscular blockade. Generally, therapy is continued for about 24 hours, at which time the benzodiazepines and or NMBs can be tapered as tolerated.
The most important therapy for the metabolic complications of strychnine poisoning is to expeditiously stop the production of metabolic byproducts by terminating the muscular hyperactivity. Hyperthermia should be treated rapidly by active cooling with ice water immersion, cooling blanket, or mist and fan, depending on the magnitude of temperature elevation. Means to prevent rhabdomyolysis induced acute kidney injury include adequate fluid administration to ensure good urine output (> 1 mL/kg/h), the potential use of urinary alkalinization with sodium bicarbonate,75 and temporary renal replacement therapy, if acute kidney failure occurs. Metabolic acidemia rapidly resolves when muscular activity is controlled.13,68
Effective management in the first few hours of strychnine poisoning is crucial for survival. If the patient can be supported adequately for the first 6 hours, this may be considered a good prognostic sign.13,34 All significantly poisoned patients should be managed in an intensive care unit with the help of a regional poison center or a medical toxicologist. For patients unintentionally exposed to strychnine who remain asymptomatic, an observation period of 12 hours is sufficient to exclude significant risk.