The relationships of plasma profenofos and ethanol concentrations to clinical outcome in acute profenofos self-poisoning.

INTRODUCTION

Many patients acutely self-poisoned with organophosphorus insecticides have co-ingested ethanol. Currently, profenofos 50% emulsifiable concentrate (EC50) is commonly ingested for self-harm in Sri Lanka. Clinical experience suggests that ethanol co-ingestion makes management more difficult. Therefore, we aimed to determine the relationships between plasma ethanol concentration, plasma profenofos concentration and its toxicokinetics, and clinical outcome in acute profenofos self-poisoning.

METHODS

Demographic and clinical data, including a history of ethanol ingestion and blood samples, were prospectively collected from all cases of acute poisoning with profenofos EC50 presenting to Teaching Hospital Peradeniya, Sri Lanka, over four years. Plasma samples were analyzed by gas chromatography-mass spectrometry to quantify the ethanol (n = 99) and profenofos (n = 30 [15 with ethanol, 15 without ethanol]) concentrations. The PKSolver program was used to calculate the toxicokinetic parameters.

RESULTS

Of 99 patients (male 78/99) with acute profenofos self-poisoning, 50 reported a history of ethanol co-ingestion. Plasma from 44 of 99 profenofos-poisoned patients had detectable ethanol concentrations. No statistical difference was observed between the mortality in the ethanol group and the no ethanol group (5/44 [11.4%] versus 3/55 [5.5%]; P = 0.461). Similarly, the median half-lives of plasma profenofos absorption in the ethanol and no ethanol groups (0.1 h and 0.1 h, respectively; time 0-24 h) were not statistically different (P = 0.6594). However, the median half-life of plasma profenofos elimination was significantly longer in the ethanol group than the no ethanol group (23.1 h and 9.9 h, respectively; time 0-24 h; P = 0.0002). According to the regression analysis, the half-life of plasma profenofos elimination was longer by 29.4 h in the ethanol group (P = 0.013).

DISCUSSION: No significant differences in outcomes, including death and endotracheal intubation rates, were found between those who did and did not co-ingest ethanol. No differences were found in toxicokinetic variables between the ethanol and no ethanol groups, but the ethanol group had a longer elimination half-life.

CONCLUSION

The co-ingestion of ethanol leads to a slowing of the elimination kinetics of profenofos. However, the study did not reveal a significant impact of ethanol co-ingestion on clinical outcomes.