C21H21NO6 = 383.178.
Hydrastine, C21H21NO6, is an alkaloid obtained from the rhizome and roots of Hydrastis canadensis, Linn. It is official in the U.S.P. It occurs as white glistening prisms, having a very bitter and pungent taste. Hydrastine melts at 132°. It may be oxidised to hydrastinine, and further oxidised to hydrastinic acid. It gives an alkaline reaction with litmus. With sulphuric acid a yellow colour is produced which becomes purple on heating. Sulphuric acid with a trace of molybdic acid gives a green colour, changing to olive-green, and then brown. Nitric acid produces a reddish-yellow colouration. Sulphuric acid with a trace of potassium bichromate yields a red colour, changing to brown. A solution in diluted sulphuric acid becomes fluorescent on the addition of solution of potassium permanganate (distinction from hydrastinine). It gives no red colour with chlorine water, by which reaction it may be distinguished from berberine, which reacts with a strong red colouration. Hydrastine is closely related to narcotine, and when oxidised the two substances yield respectively hydrastinine and cotarnine, opianic acid being split off in each case. Salts of cotarnine are much used in place of hydrastinine, owing to their lower cost. Care must be taken not to confound hydrastine with the resinoid hydrastin (see Extractum Hydrastis Siccum).
Soluble in alcohol (1 in 120), ether (1 in 83), chloroform (1 in 2), or in benzene; insoluble in petroleum ether or water.
Action and Uses.—Hydrastine closely resembles narcotine chemically, and in some respects its physiological action is similar. Its effects are exerted mainly through the central nervous system, especially exciting the medulla, its most important action being to produce a rise of blood pressure through constriction of small vessels; and to slow and depress the heart. Hydrastine is used to contract the uterus, and to arrest haemorrhage by producing constriction of peripheral vessels. The effect on the uterus is very doubtful. It is rarely, if ever, advantageous to attempt to arrest internal haemorrhage by the administration of vaso-constrictors. It is administered in pill form with extract of ergot or hamamelis; the soluble hydrastine hydrochloride may be given by hypodermic injection, 3 to 6 decimils (0.3 to 0.6 milliliters) (5 to 10 minims) of a 10 per cent. aqueous solution.
Dose.—15 to 60 milligrams (1/4 to 1 grain).