Poisoning due to water hemlock.

INTRODUCTION: Water hemlock, which encompasses a range of species divided across two genera (Cicuta and Oenanthe), are regarded as being among the most poisonous plants both in North America and in the United Kingdom. Despite their toxicity, the literature consists almost entirely of case reports.

AIM: The aim of this review is to summarize this literature by covering all aspects of taxonomy and botanical characterization, principal toxins, basic pharmacology including mechanisms of toxicity, and the clinical features, diagnosis, and management of poisoning.

MECHANISMS OF TOXICITY: The principal toxins, cicutoxin and oenanthotoxin, belong to a group of C17 conjugated polyacetylenes. They act as (noncompetitive) gamma-aminobutyric acid antagonists in the central nervous system (CNS), resulting in unabated neuronal depolarization that can lead to seizures. Ingestion of even a small amount of plant matter may result in severe intoxication.

FEATURES: After ingestion, the patient is most likely to experience CNS stimulatory effects including seizures that, in the absence of aggressive supportive care, can result in death. Other features include nausea, vomiting, diarrhea, tachycardia, mydriasis, rhabdomyolysis, renal failure, coma, respiratory impairment, and cardiac dysrhythmias.

MANAGEMENT: Treatment consists mainly of prompt airway management and seizure control, plus decontamination if achieved early and after stabilization. In the event of renal failure, the use of hemodialysis has been employed successfully.

CONCLUSIONS: The ingestion of water hemlock can lead to serious complications that may be fatal. Prognosis is good, however, if prompt supportive care is provided.