Survival after chlorfenapyr intoxication by non-gastrointestinal route

Dear Editor,

Chlorfenapyr, a pesticide widely used in agriculture, has led to a rise in poisoning cases, primarily through ingestion [1]. Previous cases have shown irreversible organ damage, often fatal, despite blood purification efforts [2]. We report a chlorfenapyr poisoning due to occupational exposure, demonstrating similar symptoms to oral poisoning.

A 39-year-old male with a history of occupational exposure to chlorfenapyr presented with symptoms including increased sweating, restlessness, fever, and difficulty urinating. The patient had been engaged in the manufacturing of chlorfenapyr powder with a concentration of 50% for a duration of 4 years, and consistently followed safety protocols. However, on September 17, 2022, the patient neglected to use protective clothing, gloves, and a breathing mask at his workplace, which has poor ventilation, due to hot weather conditions. The following day, he began experiencing symptoms such as vertigo, perspiration, and fatigue. By September 20, 2022, the patient developed restlessness, excessive sweating, and difficulty urinating, which ultimately led to his admission to our hospital. A comprehensive physical examination revealed excessive diaphoresis and facial flushing. An assessment of muscle strength revealed a muscle strength of 4/5 in both lower extremities. Magnetic resonance imaging of his brain showed numerous ischemic lesions attributable to toxicity in various regions, including the white matter, corpus callosum, and internal capsule. Toxicological analysis identified a blood chlorfenapyr concentration of 12 μg/L and a tralopyril concentration (a chlorfenapyr metabolite [3–5]) of 1,344 μg/L × h after admission. Biochemical testing showed the following: creatine kinase activity 888 U/L, creatine kinase-MB fraction activity 47 U/L, lactate dehydrogenase activity 417 U/L, alanine aminotransferase activity 60.8 U/L, aspartate aminotransferase activity 40.9 U/L, and creatinine concentration 52 μmol/L (0.59 mg/dL). Based on the patient’s chlorfenapyr exposure history, toxicology results, and clinical symptoms, we diagnosed chlorfenapyr poisoning. We used a 6-day treatment cycle consisting of 2 hours of hemoperfusion, 10 hours of continuous kidney replacement therapy, 2 hours of hemoperfusion, and 2 hours of plasma exchange. Serial chlorfenapyr and tralopyril concentration were obtained (Table 1). Following admission, the patient experienced a noticeable period of progressive muscle weakness. However, with the implementation of the aforementioned treatment, the patient’s symptoms gradually stabilized, ultimately leading to their eventual discharge. Moreover, during the one-year follow-up, the patient demonstrated significant improvement in their daily living capacities.

Table 1. Toxin screening of the patient’s blood, ultrafiltrate and urine during extracorporeal therapies.

Days after admission	Tralopyril concentration before the treatment cycle (blood)	Tralopyril concentration after the treatment cycle (blood)	Tralopyril concentration (ultrafiltrate)	Tralopyril concentration (urine)	Chlorfenapyr concentration (blood, urine, ultrafiltrate)
2	965 μg/L	634 μg/L	798 μg/L	92 μg/L	negative
3	785 μg/L	467 μg/L	579 μg/L	79 μg/L	negative
4	595 μg/L	367 μg/L	308 μg/L	48 μg/L	negative
5	334 μg/L	141 μg/L	168 μg/L	33 μg/L	negative
6	172 μg/L	57 μg/L	81 μg/L	15 μg/L	negative
7	88 μg/L	15 μg/L	18 μg/L	6 μg/L	negative

The average daily production of ultrafiltrate is 40 L, which is sequentially collected into 10 collection bags. From the final collection bag containing 4 L, we obtained a 10 mL sample for analysis. The average daily production of urine was 2,200 mL, from which we collected a 10 mL sample for analysis each day.

Acute chlorfenapyr poisoning currently lacks specific antidotes. In addition to promptly eliminating chlorfenapyr remaining in the gastrointestinal tract and dermal layers on the skin, other treatment modalities encompass supportive care targeting rhabdomyolysis and organ dysfunction. In this case of successful treatment for chlorfenapyr poisoning, the early initiation of extracorporeal techniques may have contributed to this patient’s good outcome. Continuously monitoring the concentrations of chlorfenapyr and tralopyril in the patient’s blood, urine, and ultrafiltrate can be beneficial for understanding the changes in toxin concentrations before and after each extracorporeal cycle, and for evaluating the effectiveness of the blood purification therapy.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by The Medical Science Research of Hebei Province, China (No. 20230550).