Gelsemium is an Asian and North American genus of flowering plants belonging to family Gelsemiaceae.

It also proved valuable in some cases of malarial fever, and was occasionally used as a cardiac depressant and in spasmodic affections, but was inferior for this purpose to other remedies.

In a letter written by him to the British Medical Journal on 20 September 1879, he described that he had persistent diarrhea, severe frontal headache, and great depression, and therefore stopped his self-experimentation at 200 minims.

[15][16][17] In his classic early 20th century work on psychotropic drugs Phantastica, German pharmacologist Louis Lewin recounts the seemingly unique case of a person who became addicted (in a manner far more often associated with opiates) to a Gelsemium preparation: during a severe attack of rheumatism a man took a large quantity of an alcoholic tincture of Gelsemium sempervirens a plant which is liable to act on the brain and the medulla oblongata.

As he continued to increase the doses he fell into idiocy and died in a state of mental confusion.