ACONITE 341 



Aconite and Aconitine. 



Action External. — Aconite or aconitine applied to mucous mem- 

 branes, raw surfaces or the unbroken skin, irritates and then paralyzes 

 the nerves of touch and temperature. This is evidenced in the human 

 subject by a sensation of tingling and burning, followed by numbness and 

 local anesthesia. 



Action Internal. — Digestive Tract. — Aconite in medicinal doses has 

 no special effect on the digestive organs. Toxic doses produce nausea 

 and retching, and, in animals capable of the act, vomiting. 



Circulation. — The chief therapeutic value of aconite depends upon 

 its influence over the heart and vessels. It reduces the frequency of the 

 cardiac pulsations, owing to stimulation of the vagus centre in the 

 medulla, and lowers blood tension. This is the chief effect of aconite 

 on the circulation in medicinal doses. The action on the heart is not to 

 weaken it in therapeutic doses but simply to slow it — pure inhibition. It 

 is improper, therefore, to classify aconite as decreasing the force of the 

 heart, save in toxic doses. In medicinal doses it makes the systolic con- 

 tractions more powerful and causes increased dilatation in diastole. It 

 may, however, be regarded as a circulatory depressant in slowing the 

 heart and lessening the output of blood, since it thus weakens blood pres- 

 sure. In fatal poisoning by the drug the action of the heart becomes 

 rapid and irregular. The time of contraction of the auricles does not 

 correspond with ventricular contraction (heart block) and the lack of 

 rhythm and irregularity increase until the heart is thrown into delirium 

 and fibrillation, as with digitalis. 



Depending on this condition of the heart, the blood pressure is 

 naturally subject to momentary variations. The rapidity and irregularity 

 of the heart are due to paralysis of the inhibitory apparatus and great 

 irritability of the cardiac muscle, with weakened contraction and conduc- 

 tion, occurring simultaneously. 



The vasoconstrictor-centre is slightly stimulated by medicinal doses, 

 but the blood pressure is lowered through the slowing of the heart beats, 

 prolonged diastole, and lessened cardiac output. In poisoning there is 

 paralysis of the vasomotor centres. 



The heart is arrested in diastole, but death immediately results from 

 respiratory failure. 



Nervous System. — The most striking effect of aconite on the nervous 

 system (in man) consists in tingling followed by loss of sensation and 

 temperature sense after large medicinal doses. This phenomenon is due 

 to stimulation succeeded by depression of the sensory nerve terminations. 

 The drug is not comparable with opium, since doses large enough to pro- 

 duce a general anodyne action are dangerous. 



Poisonous doses of aconite cause muscular twitching and loss of 

 motor power, which result from excitation, and finally paralysis of the 

 motor nerve endings. Convulsions occur in poisoning. These are thought 

 to follow stimulation of the medulla as the higher cerebral centres are 

 often unimpaired. Stimulation and then depression of the lower divisions 



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