The chief constituents of colchicum are two alkaloids, colchicine and veratrine.
Colchicine is the active principle and may be given in full form in doses of to 1 1 8 grain.
The British Pharmacopoeia contains (i) an extract of the fresh corm, having doses of 4 to i grain, and (2) the Vinum Colchici, made by treating the dried corm with sherry and given in doses of 10 to 30 minims. This latter is the preparation still most generally used, though the presence of veratrine both in the corm and the seeds renders the use of colchicine itself theoretically preferable.
They contain a volatile oil which does not occur in the corm, and their proportion of colchicine is higher, for which reason the Tinctura Colchici Seminum- dose 5 to 15 minims - is preferable to the wine prepared from the corm.
The salicylate of colchicine is stable in water and may be given in doses of about one-thirtieth of a grain.
Colchicum or colchicine, when applied to the skin, acts as a powerful irritant, causing local pain and congestion.
Taken internally, colchicum or colchicine markedly increases the amount of bile poured into the alimentary canal, being amongst the most powerful of known cholagogues.
In larger doses colchicum or colchicine acts as a most violent gastrointestinal irritant, causing terrible pain, colic,vomiting, diarrhoea, haemorrhage from the bowel, thirst and ultimately death from collapse.
The action of colchicum or colchicine upon the kidneys has been minutely studied, and it is asserted on the one hand that the urinary solids are much diminished and, on the other hand, that they are markedly increased, the specific gravity of the secretion being much raised.
When that is done, colchicine may be found to exhibit a definite chemical interaction with this hitherto undiscovered substance.