Much less nicotine is used in agriculture today than in the past, but it is still used in horticultural applications. An oral dose of no more than 40 mg of nicotine appears to be fatal to humans. Direct exposure to nicotine causes nausea, dizziness, vomiting, sweating, and tachycardia.
Diagnosis and treatment
The diagnosis is related to the medical history. Plasma levels can be determined in only a few laboratories. There are no specific antidotes, so besides fighting the seizures with diazepam in a vein, the only solution is supportive therapy.
Source: Vadecum of poisoning therapy by Roy Goulding