This section is from the book "Materia Medica And Therapeutics - Vegetable Kingdom", by Charles D. F. Phillips. Also available from Amazon: Materia Medica And Therapeutics: Vegetable Kingdom.
Active Ingredients. - The active ingredients of gelsemium were first investigated by Wormley,1 who succeeded in isolating an alkaloid gelsemia which existed in combination with an acid termed by him gelseminic acid. He was led to these researches by a case of fatal poisoning from gelsemium that came under his notice.
Physiological Action. - This has been investigated by Bartho-low and others. According to Ott, gelsemia produces in man double vision, ptosis, want of co-ordination, disagreeable feeling in the head, great muscular relaxation, drooping of lower jaw, tongue stiff, sensation blunted, pupils dilated, respiration slow, irregular, pulse slow, surface cold and congested, unconsciousness, and death by asphyxia. Ringer and Murrel state that during the diplopia the images in the upper part of the field of vision appear at different heights, although actually in the same plane. Locally the drug contracts the pupil, while internally it contracts and dilates it, paralyzing the third pair. The drug affects the sixth nerve before the third, as the external rectus is the first muscle weakened. Taylor states that it increases the urine and reduces the pulse, respiration, and temperature. Tweedy states that it impairs the power of accommodation of the eye for near objects.
Therapeutic Action. - The precise sphere of the therapeutic action of gelsemium has not as yet been clearly defined. Its first and perhaps most frequent use has been the treatment of the bilious remittent fevers of the Southern States, its value in this connection having been accidentally discovered. The prostration produced by excessive doses has suggested its use in cases of cerebral excitement and spinal congestions, and led to its successful employment in delirium tremens, chorea, epilepsy, tetanus, and other disorders. It is also serviceable in the acute stage of an acute gonorrhoea, and in trigeminal neuralgia.
Preparations and Dose. - Extract. Gelsemii Fluidum, mj. xv. (.06. - 1). Fluid extracts of gelsemium vary in quality to a degree that makes it almost impossible to fix the dose in a given case with any accuracy, unless the extract employed has been carefully tested in advance. In the majority of cases it is best to commence with a small dose frequently repeated until the early physiological effects (diplopia, etc.) are developed. In neuralgia its effects appear to be specific, and in suitable cases small doses answer as well if not better than large ones.)
1 Amer. Jour, of Phar., Jan., 1870.