28 Years old gentleman, no known
medical illness but presented multiple times to casualty for self inflicting
injury currently presented with history of alleged drinking one glass of
"roundup" two hours prior to presentation after fighting with his
wife. He denied suicidal attempt or hallucination but claims drinking it to
scare his wife. He exhibit only mild gastrointestinal symptoms including
epigastric pain, nausea and vomiting. Upon presentation, he was fully conscious
and alert, stable vital signs, intact higher mental status function but poor
insights. There was also neglected cut wound over his left dorsum of hand. His
ECG and cardiac monitoring is normal. He was treated symptomatically with IV
maxolon 10 mg, IV Ranitidine 50 mg, IV Hycosine 20 mg and activated charcoal.
Ryle’s tube was inserted but gastric lavage was not done. He was then admitted
to general medical ward for observation.
Roundup is a trade name for herbicide that contains Glyphosate and
manufactured by Monsanto.
Glyphosate exist as a chemical
structure N-(phosphonomethyl)glycine
with carbon and phosphorus moiety. Differs from the organophosphate containing herbicide,
it has no anti cholinesterase effects.
This non selective, broad-spectrum
systemic herbicide consists of mixture of water, 15% of polyoxyethyleneamine
(POEA), and glyphosate (isopropylamine salt). Depending on either it is
produced for commercial use of domestic use, it contains 41% to 1% glyphosate
formulations.
Glyphosate inhibits enzyme used for
synthesis of aromatic amino acids tyrosine, tryptophan and phenylalanine. POEA
is a surfactant that assist in penetration of the chemicals into the herbs
tissue.
Even though categorized as category
III in term of toxicity (Grade I to IV with I is the most toxic), survey by UK
National Poisons Information Service 2005 revealed that it is the fourth most
common exposure and third most common implicated in self harm cases. (E Beswick & J Millo)
The mechanism of
toxicity in glyphosate formulation is complicated. It is difficult to tell
whether toxicity arises do to the effect of glyphosate, surfactants or both.
Experimental studies proposed that
POEA toxicity is greater than glyphosate alone and commercial formulations
alone. However, there is insufficient data to conclude whether POEA containing
preparation is more toxic than other surfactant containing preparation.
Proposed mechanisms of Glyphosate
toxicity to mammals include uncoupling of oxidative phosphorylation and
glyphosate- or POEA-mediated direct cardiotoxicity. (E Beswick & J Millo)
Accidental ingestion of glyphosate
usually give mild and transient gastrointestinal irritation. Ingestion of >85 ml of concentrated
formulation is likely to cause significant toxicity in adult (Bradberry SM et al)
Gastrointestinal corrosive effects,
with mouth, throat and epigastric pain and dysphagia are common. Renal and
hepatic impairment are also frequent and usually reflect reduced organ
perfusion. Respiratory distress, impaired consciousness, pulmonary oedema,
infiltration on chest x-ray, shock, arrhythmias, renal failure requiring
hemodialysis, metabolic acidosis and hyperkalaemia may supervene in severe cases.
Bradycardia and ventricular arrhythmias are often present pre-terminally.
Dermal exposure to ready-to-use glyphosate formulations can cause irritation
and photo-contact dermatitis has been reported occasionally; these effects are
probably due to the preservative Proxel (benzisothiazolin-3-one). Severe skin
burns are very rare. Inhalation is a minor route of exposure but spray mist may
cause oral or nasal discomfort, an unpleasant taste in the mouth, tingling and
throat irritation. Eye exposure may lead to mild conjunctivitis, and
superficial corneal injury is possible if irrigation is delayed or inadequate. (Bradberry SM et al)
Patient with high fatality rate
usually exhibit these features; 1)Ingestion of more than 150 mL Glyphosate, 2)
Pulmonary oedema, 3)Hypotension refractory to fluid resuscitation, inotropes or
vasopressors, 4) Corrosive effects on the gastrointestinal tract, 4) Tachy- and
brady arrhythmias, 5) Renal failure, 6) Elevated liver enzymes, 7)
Hyperkalaemia, 8) Metabolic acidosis, 9) Older patients (E Beswick & J Millo)
There is no specific antidote for
glyphosate poisoning and the treatment is mostly supportive and organ related treatment.
Reference
1. Bradberry SM, Proudfoot AT, Vale
JA, "Glyphosate poisoning.", Toxicol Rev. 2004;23(3):159-67.
2. E Beswick, J Millo, "Fatal
poisoning with glyphosate surfactant herbicide", JICS Volume 12, Number 1,
January 2011
3. Pesticide Action Network Asia
and the Pacific on Glyphosate, November 2009
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