74 CIRCULATORY STIMULANTS 



DIGITALIS 



Synonym, Fox Glove 



Parts Used. The leaves of Digitalis purpurea, collected from 

 plants of the second year's growth. It is an ornamental flower of 

 gardens, grows wild in Europe, Oregon and Australia, and is culti- 

 vated for the drug market in England and Germany. 



Preparations and Doses. 



Fluidextradum Digitalis. H. ITt xv — Ix. (1. — 4.) ; D. V(l % — 

 iij (0.03—0.2). 



Digitalis (leaves). The same dose as above in grains. 



Tinctura Digitalis, 10 per cent. H. 3ij — viij (8.— 30.) ; D. TTL 

 ij— XXX (0.13—2.). 



Infusum Digitalis. H. §ij — vj (60. — 180.) ; Dog. 3j — iv (4. — 

 15.). 



Toxic dose of the leaves. H. 3vj — ^viij (24. — 30.) ; Dog. 3j — iv 

 (4.-15.). 



Active Constituents. The chief ingredients of digitalis are 

 glucosides and it is therefore subject to early destruction. The fol- 

 lowing are the more important : 



Digitoxin, Digitoxin most nearly represents the digitalis action. 

 It is practically insoluble in water, but soluble in alcohol. It is 

 present in the leaves to the extent of about 0.2—0.4 per cent. 



Digitalin is the next of importance. It is slightly soluble in 

 ■water, is soluble in 100 parts of diluted alcohol, and readily soluble 

 in alcohol. 



Digitalein. This is similar to digitalin. It is soluble in water 

 and alcohol. 



Under the influence of heat or acids, or when kept for some time 

 in aqueous solutions, these glucosides tend to decompose and may form 

 toxiresins which have a central convulsive action. 



In addition to the above, digitalis contains digitonin, a saponin 

 body, which foams with water and possesses the peculiar property of 

 holding the otherwise insoluble active principles in solution in 

 water. It is on this account that the aqueous infusion represents the 

 activity of the drug. If administered intravenously, digitonin is the 

 physiological antagonist to digitoxin, but it is not absorbed from the 

 digestive tract. 



Summary of Action. 1. A direct action upon cardiac muscle 

 increasing its irritability and contractility, leading to a more powerful 

 systole and finally lengthened diastole. 

 " 2. Vagus stimulation chiefly on account of increased blood supply 

 but also partly direct. 



3. Vasoconstriction by action both upon the arterial muscles and 

 by central action. 



4. Diuretic action in heart disease. 



