This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
A neutral principle prepared from the seeds of Anamirta paniculata.
Characters. - Colourless, flexible, shining, prismatic crystals, permanent in the air, odourless, having a very bitter taste, and a neutral reaction.
Reactions. - When heated to about 200° C. (392° F.), the crystals melt, forming a yellow liquid; when heated on platinum foil, they char and are finally completely dissipated. Concentrated sulphuric acid dissolves picrotoxin with a golden-yellow colour, which turns violet-red on the addition of a trace of bichromate of potassium. When mixed with three times its weight of nitrate of potassium, moistened with sulphuric acid, and then treated with strong solution of soda in excess, picrotoxin assumes a brick-red colour of short duration. The aqueous solution should remain unaffected by solutions of salts of mercury or platinum, tannic acid, iodide of mercury and potassium, or other reagents for alkaloids (absence of, and difference from, alkaloids).
Dose. - 1/120 to 1/60 gr. in pill, or in the acetic solution described under Uses.
Action. - It stimulates all the motor and inhibitory centres in the medulla, especially the respiratory and vagus centres. It also irritates motor centres, either in the cerebrum or in the medulla and cord, producing in all vertebrates alternating epileptiform spasms, with periodic stoppage of the motions of the diaphragm and slowness of the pulse. The spasms often take the form of swimming, running backwards or round in a circle (manege movements), or rolling of the body on its axis (pp. 188 and 215). The temperature is somewhat raised.
Uses. - It is employed as an ointment (10 gr. to 1 oz. of lard) in tinea capitis, and to destroy pediculi. It should be used with care, as its application to the head has been followed by convulsions and death. It has been used, though unsuccessfully, in epilepsy in doses of 1/25 grain hypodermically, and has been found useful in the night sweats of phthisis (p. 443), in doses of 1/120 to 1/60 grain in pill, or 2 to 4 minims of a solution containing 8 grains of picrotoxin, 4 fluid drachms of glacial acetic acid, and water up to 4 ounces.