Glyphosate-Surfactant Herbicide (Roundup etc.) Poisoning

Overview

Glyphosate (N-phosphonomethylglycine) is the most widely used herbicide in the world, inhibiting the EPSP synthase enzyme in plants; the acute toxicity of pure glyphosate in mammals is relatively low, and the severity of the clinical picture primarily comes from the formulation components. The systemic toxicity in human poisoning from commercial products (such as Roundup) is largely attributed to the SURFACTANT component.

The surfactant polyoxyethyleneamine (POEA, polyethoxylated tallow amine) is present in the formulation at approximately 7-15%, and experimental studies show higher toxicity than glyphosate alone; many sources consider the surfactant to be the most toxic component (Roberts 2010). However, it is difficult to definitively distinguish the relative contribution of glyphosate itself and co-formulants, and this distinction is debated in the literature (Bradberry 2004).

The proposed cellular mechanism is that the surfactant directly disrupts cell membranes and uncouples mitochondrial oxidative phosphorylation, thereby impairing energy production; this explains the hypoxic energy deficit of tissues along with corrosive damage in the gastrointestinal and respiratory epithelia. Toxicokinetically, glyphosate is rapidly but incompletely absorbed orally, reaching peak plasma levels in approximately 4-6 hours, is largely excreted unchanged by the kidneys without significant metabolism in the liver, and has an elimination half-life of about 3-4 hours; in renal failure, this half-life is significantly prolonged, and glyphosate can be detected in serum for days.

The clinical picture is closely related to dose and concentration: small accidental ingestion leads to mild corrosive gastrointestinal irritation such as oral-throat burning, nausea-vomiting, and dysphagia; large concentrated ingestion can progress fulminantly with corrosive esophagogastric injury and bleeding, hypotension and circulatory collapse, high anion gap metabolic acidosis, acute kidney injury, pulmonary edema and acute respiratory distress syndrome (ARDS), hyperkalemia, cardiac arrhythmia, and altered consciousness. In a series including symptomatic cases, hypotension was reported in approximately 47%, impaired consciousness in 39%, respiratory failure in 30%, acute kidney injury in 17%, and arrhythmia in 10%; death is primarily due to pulmonary edema, shock, and arrhythmia.

Electrocardiographic changes can range from sinus tachycardia to QTc prolongation, conduction blocks, and, in rare cases, ventricular tachycardia. Plasma glyphosate levels are associated with clinical severity; in the prospective series by Roberts and colleagues, plasma glyphosate levels above 734 micrograms/mL at presentation were found to be the strongest independent predictor of death, and the odds ratio for this threshold was calculated to be approximately 106; however, since this value only reflects the lowest peak level in five fatal cases, independent validation in a larger dataset is required.

In a study examining a smaller number of patients (18 cases), a threshold of 600 mg/L for blood glyphosate levels predicted severe poisoning with 67% sensitivity and 100% specificity, and a threshold of 0.88 mg/L for glyphosate's metabolite aminomethylphosphonic acid (AMPA) predicted it with 71% sensitivity and 100% specificity (Cellier 2022). In a more recent study involving one hundred fifty-one patients, plasma glyphosate and AMPA levels predicted clinical severity, while the blood level of the POEA surfactant, despite being detectable in only a minority of patients, predicted acute kidney injury MORE STRONGLY than glyphosate itself (Qiang 2024); this finding directly supports the central role of the surfactant in renal toxicity.

Since these plasma level measurements are not performed in routine emergency laboratories in Turkey, clinical and standard laboratory (blood gas, potassium, creatinine, electrocardiography) risk stratification forms the basis of daily practice. THERE IS NO SPECIFIC ANTIDOTE; management is based on early supportive care, decontamination, and prognostic risk stratification.

Key considerations

• Paraquat and diquat poisoning are the most dangerous herbicide ingestions mixed with glyphosate; in paraquat, oxygen is RESTRICTED because it increases free oxygen radical damage, whereas oxygen is not restricted in glyphosate, so this distinction directly changes treatment, and if the history is unclear, seeing the product packaging is critical.
• Corrosive acid or alkali ingestion overlaps with the oropharyngeal and esophageal burn presentation of glyphosate; however, in strong acids/alkalis, full-thickness esophageal necrosis and the risk of late stricture are more pronounced, and endoscopic staging is key in making this distinction.
• Organophosphate and carbamate anticholinesterase pesticide poisonings produce a cholinergic toxidrome with miosis, hypersalivation, bronchorrhea, bradycardia, and fasciculations; the absence of this toxidrome supports glyphosate.
• Toxic alcohol (methanol, ethylene glycol) poisoning also causes high anion gap metabolic acidosis and shock; however, here a prominent osmolar gap and oxalate crystalluria accompanied by visual impairment or renal failure are distinctive.
• Metformin-associated lactic acidosis creates a similar severe metabolic acidosis and hemodynamic disorder; a history of drug use and underlying kidney failure help distinguish it.
• Sepsis and septic shock overlap with hypotension, lactic acidosis, and multiple organ failure; they are distinguished by the presence of fever, an infection focus, and the absence of a history of ingestion.
• Acute respiratory distress syndrome and non-cardiogenic pulmonary edema due to other causes mimic the pulmonary involvement of glyphosate; however, a history of herbicide ingestion and accompanying corrosive gastrointestinal findings guide the diagnosis.
• Non-corrosive gastroenteritis and food poisoning due to other substances may be confused with nausea and vomiting in mild glyphosate ingestion; the presence of corrosive lesions in the oral mucosa and a history of ingestion favors glyphosate.
• Poisoning with membrane-stabilizing drugs such as tricyclic antidepressants can mimic glyphosate’s cardiac toxicity by causing arrhythmia with QRS and QTc prolongation; a history of drug use and typical anticholinergic findings allow differentiation.
• Ingestions of caustic substances (detergent, bleach, industrial chemicals) also present with oropharyngeal and esophageal burns; providing the product packaging or safety data sheet is decisive in determining which substance was ingested and accordingly planning supportive management.
• Salicylate poisoning can also present with high anion gap metabolic acidosis, tachypnea, and altered consciousness; however, salicylates typically have an accompanying primary respiratory alkalosis, and measuring serum salicylate level clarifies the distinction.

Why it matters

The treatment approach is based on pathophysiology and evidence. (1) Since there is no specific antidote and toxicity arises from formulation/surfactant-mediated corrosive and systemic effects, management is entirely SUPPORTIVE; early aggressive fluid resuscitation, vasopressors, acid-base and electrolyte correction, and respiratory support are the cornerstones (Bradberry; Roberts). (2) Glyphosate is rapidly absorbed (half-life ~3 hours, Roberts), so the window for gastric decontamination is narrow; activated charcoal is only considered for large and very recent ingestions if the airway is protected — its benefit has not been proven; gastric lavage is not recommended due to corrosive injury/lack of evidence. (3) Hemodialysis has not shown a toxin-removal benefit for glyphosate/surfactant; indications for dialysis are standard organ-support reasons such as kidney failure, refractory acidosis, and hyperkalemia. (3b) The evidence base for intravenous lipid emulsion goes beyond single case reports noted in the first_line/alternatives section of the protocol: In the study by Gil et al. including 64 patients, where 22 patients who received lipid emulsion were matched by the amount ingested and the time since ingestion with 22 control patients, none of the patients receiving lipid emulsion developed hypotension, while approximately 41% of the control group developed hypotension, and no arrhythmias were observed in the lipid emulsion group (Gil 2013).

This evidence is stronger than a single case report; however, it is a matched observational design, not randomized, and therefore has not been elevated to a standard first-line treatment recommendation. (4) Prognosis is dose-dependent, and risk stratification guides disposition: from concentrated (~41%) formulations, >85 mL is a significant toxicity threshold (Bradberry), >100 mL leads to complications (Moon & Chun), ~190 mL is the mortality threshold (Roberts), and >200 mL indicates serious outcomes (Lee); however, volume alone is an imperfect predictor (Talbot: some patients had mild outcomes even after 500 mL). (5) Poor prognostic indicators — advanced age (>50), metabolic acidosis, hyperkalemia, high creatinine and oliguria, abnormal chest X-ray and respiratory failure, tachycardia, low Glasgow Coma Scale — require early intensive care and aggressive support. In a recent series from a poison center covering 109 patients, about one-third of the patients showed poor prognosis and 5.5% died; in multivariate analysis, admission Glasgow Coma Scale, albumin, blood pH, QTc interval, and estimated glomerular filtration rate were found as independent predictors of in-hospital mortality, and in dominance analysis, the variable contributing most to the risk of death was pH (about 36%), followed by QTc (20%), Glasgow Coma Scale (17%), and estimated glomerular filtration rate (17%) (Liu 2024).

This finding reinforces the value of assessing blood gases, electrocardiography, and kidney function together in risk stratification at admission. (6) Evidence regarding the role of hemodialysis is evolving: the classic view was that there was no evidence that dialysis changed outcomes and the indication was not toxin clearance but standard organ-support reasons (Roberts 2010); in contrast, more recent case reports have shown that glyphosate can be effectively cleared by hemodialysis (with an extraction rate of about 92% in one case). Nevertheless, because it has not been proven in controlled studies that this kinetic clearance translates into clinical outcomes, the decision for dialysis is still based on organ-support indications such as severe kidney injury, refractory metabolic acidosis, and refractory hyperkalemia.

Critical complications

• Pulmonary edema and acute respiratory distress syndrome are leading causes of glyphosate deaths and were detected in about 58% of deaths in one series; they are recognized by progressive dyspnea, hypoxemia, and diffuse infiltrates on chest X-ray, and are managed with early intubation, protective low tidal volume ventilation, and careful fluid balance.
• Corrosive esophagogastric injury and gastrointestinal bleeding occur with large concentrated ingestions; they present with dysphagia, inability to swallow saliva, hematemesis, and abdominal pain, and notable findings require endoscopic staging, proton pump inhibitors, and surgical evaluation for bleeding/perforation.
• Refractory hypotension and circulatory collapse develop due to corrosive fluid loss and the vasodilator-cardiodepressant effect of surfactant; they are managed with aggressive crystalloid and norepinephrine, and in resistant cases, vasopressin is added, with failure to improve being a sign of poor prognosis.
• High anion gap metabolic acidosis and hyperkalemia are among the main mechanisms of death; they are recognized with serial blood gas and potassium monitoring, corrected with sodium bicarbonate for severe acidosis, calcium gluconate for hyperkalemia, insulin-glucose, and dialysis if necessary.
• Cardiac arrhythmia and QTc prolongation are due to membrane toxicity; they are monitored with continuous monitoring and serial electrocardiography, drugs that prolong QTc are avoided, electrolytes (potassium, magnesium, calcium) are optimized, and the rare ventricular tachycardia is treated according to standard advanced life support principles.
• Acute kidney injury arises both from direct toxicity and in the context of shock and rhabdomyolysis; it is recognized by oliguria and rising creatinine, managed with fluid optimization and avoidance of nephrotoxins, and renal replacement therapy is required in resistant acidosis-hyperkalemia.
• Aspiration pneumonia is an iatrogenic complication associated with both corrosive vomiting and incorrectly timed activated charcoal or gastric lavage; therefore, decontamination is not done without airway protection, and charcoal is considered only in selected early cases with a protected airway.
• Hepatic dysfunction is indicated by elevated transaminases, and alanine aminotransferase levels above 40 U/L are predictors of complicated course; it generally resolves with supportive monitoring, and in severe cases, liver functions are followed serially.
• Esophageal stricture is a late complication appearing as dysphagia over weeks to months during the healing phase of corrosive injury; in patients with significant esophagogastric damage detected at initial admission, this possibility is kept in mind at post-discharge follow-up, and endoscopic dilation is planned if necessary.

Special considerations

• In elderly patients, especially those over 50, the risk of complications and death increases independently (Moon & Chun 2010); in this group, the disposition threshold should be low, the same volume intake should be considered more serious, and early intensive care evaluation should be performed.
• In patients with renal failure, since glyphosate is excreted unchanged by the kidneys, the elimination half-life is significantly prolonged and the toxin can remain in the serum for days; in this group, both the duration of toxicity is prolonged and fluid-electrolyte management becomes more difficult, and the threshold for renal replacement is considered earlier.
• In patients with liver dysfunction or those with elevated alanine aminotransferase levels at presentation, the likelihood of a complicated course increases; this marker should be included in risk stratification and liver functions should be monitored serially.
• Data on acute maternal glyphosate-surfactant poisoning during pregnancy are limited; the management principle is that resuscitating the mother also protects the fetus, therefore correcting oxygenation, perfusion, and acidosis is prioritized, fetal monitoring at an appropriate gestational age and cooperation with obstetrics should be ensured, and the absence of an antidote does not change treatment.
• In children, exposures are often accidental and small in volume; asymptomatic minor licking/contact is generally monitored with close observation, but in symptomatic children or those ingesting concentrated products, the same principles as adults apply and all doses (fluids, charcoal, vasopressors) are adjusted according to weight.

Follow-up plan

All significant exposures are monitored in a monitored/intensive care setting. Serial blood gases, lactate, potassium, creatinine/urine output, complete blood count, liver functions, and ECG (including QTc) are followed; since pulmonary edema and acute kidney injury are the main mechanisms of death, respiratory and renal status are closely monitored.

Endoscopic evaluation of esophagogastric injury is considered in marked corrosive findings. Even clinically mild/stable patients should be observed for at least 6-24 hours; progressive acidosis, hyperkalemia, or worsening respiration escalates to red.

In self-harm exposures, psychiatric evaluation is required after medical stabilization. At every stage, communication with UZEM 114 / toxicology and transfer to a higher-level center is recommended if necessary.

The discharge criteria; small accidental exposures that are asymptomatic or have only transient mild oral-pharyngeal irritation, tolerate oral intake, are hemodynamically stable, have normal blood gases and electrolytes, and have a reliable observer can be followed as outpatients after at least 6 hours of observation; for large volume, concentrated product, elderly, or comorbid patients, the threshold is raised and monitoring is extended. Ambulatory patients are given warnings about deterioration: they are instructed to go to the emergency department immediately if they experience progressive shortness of breath, chest pain, recurrent vomiting or vomiting blood, difficulty swallowing, decreased urination, a feeling of fainting, or confusion.

It is not forgotten that in patients who have taken concentrated products or have corrosive findings, the conditions may appear mild in the first hours and worsen later; therefore, early discharge is avoided. In those who develop corrosive esophagogastric injury, a follow-up for dysphagia and esophageal stricture is planned during the recovery period, and dilation may be arranged if necessary.

In all ingestions for suicidal purposes, psychiatric evaluation and a safe discharge plan are mandatory after medical stabilization.