2-Methyl-4-chlorophenoxyacetic acid (MCPA) and bromoxynil herbicide ingestion

Abstract

Context: Ingestion of bromoxynil and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in combination is associated with high mortality. Toxicity is characterised by hyperthermia and metabolic acidosis. Dialysis is a proposed treatment, but little data exist regarding its effectiveness.

Case details: Case 1: A 50-year-old female presented 18 h post-ingestion of 200  mL of bromoxynil(200 g/L) and MCPA(200 g/L). She was agitated, tachycardic and tachypnoeic. She was intubated and continuous venovenous haemodiafiltration (CVVHDF) was commenced. She deteriorated, becoming hypotensive, hyperthermic (39.5 °C) and hypercapnic (80 mmHg). She was cooled, paralysed, received CVVHDF for 2d and was extubated on day 4 making a full recovery. Case 2: A 60-year-old male presented 6 h post-ingestion of an unknown amount of bromoxynil (200 g/L) and MCPA (200 g/L). On arrival, he was tachycardic and tachypneic (pCO₂ 25 mmHg). At 8h post-ingestion he became hyperthermic, hypercapnic and acidotic (pH 7.15), and was intubated, paralysed, cooled and received CVVHDF for 36 h. He was extubated after 42 h and made a full recovery. Bromoxynil and MCPA serum and effluent concentrations were measured. Peak MCPA serum concentrations were 161 µg/ml and 259 µg/ml and peak bromoxynil concentrations were 119 µg/ml and 155 µg/ml in case 1 and 2, respectively. The estimated clearance of both herbicides by CVVHDF was low (<10 mL/min).

Conclusion: CVVHDF did not result in significant clearance of either herbicide but may have assisted with hyperthermia control. Both patients survived with vigorous cooling, paralysis and ventilatory support.

Keywords:

• Herbicide
• overdose
• poisoning
• extracorporeal elimination

Disclosure statement

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

Colin Page is supported by an Emergency Medicine Research Foundation Research Fellowship. Geoff Isbister is funded by an National Health and Medical Research Council Senior Research Fellowship ID1061041. Mike Roberts is funded by an National Health and Medical Research Council Senior Principal Research Fellowship ID1002611. This research was partially supported by an National Health and Medical Research Council Program Grant 1055176.