Poison Hemlock - Spinal and Peripheral Neurotoxic Agents

POISON HEMLOCK

Botanical Name

Conium maculatum.

Physical Appearance

·              Hemlock belongs to the family Umbelliferae of genus Cicuta, and is a biennial herb that grows erect to an average height of 1 to 3 metres (Fig 21.6).

·              The larger stems are hollow and bear numerous purple spots that are very distinctive.

·              Leaves are fine, light-green, and fern-like. When crushed, they give off an unpleasant “mousy” smell.

·              Fruits are smooth skinned with crenate ribs, and are binocu-lated, measuring about 9 mm long, and 6 mm across.

Toxic Part

All parts.

Toxic Principles

The toxins of poison hemlock are simple piperidine alkaloids: coniine and gamma-coniceine. They are structurally similar to nicotine and possess similar clinical features in toxicity.

Mode of Action

The mode of action is two-fold. The most serious effect occurs at the neuromuscular junction where these alkaloids act as non-depolarising blockers causing respiratory failure due to flaccid paralysis. The second effect at the auto-nomic ganglia is nicotinic in nature resulting in salivation, mydriasis, and tachycardia, followed by bradycardia. Less commonly, rhabdomyolysis and acute tubular necrosis can occur.

Clinical Features

·      Nausea, vomiting, abdominal pain.

·      Stimulant phase: tachycardia, tremors, sweating, mydriasis,convulsions.

·              Depressive phase: bradycardia, ascending motor paralysis,and coma.

Treatment

·      Aggressive GI decontamination: lavage and activated charcoal.

·      Benzodiazepines for convulsions.

·      Respiratory support.

·      Forced diuresis may help in preventing renal failure.

Forensic Issues

·              Hemlock was popular in ancient times as a means of execu-tion. The most famous personality executed in this fashion was Socrates, who was condemned to death for his “crime” of introducing new divinities.

·              Today, most cases of hemlock poisoning result from accidental circumstances due to mistaken identity with edible vegetables such as wild carrot, parsley, or anise seeds.