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.
At present this otherwise excellent preparation is not standardized, but the suggestion has been made that it should be standardized to contain o 1% of colchicine.