Taken from On Cocaine

A few minutes after taking cocaine, one experiences a certain exhilaration and feeling of lightness. One feels a certain furriness on the lips and palate, followed by a feeling of warmth in the same areas; if one now drinks cold water, it feels warm on the lips and cold in the throat. One other occasions the predominant feeling is a rather pleasant coolness in the mouth and throat.

During this first trial I experienced a short period of toxic effects, which did not recur in subsequent experiments. Breathing became slower and deeper and I felt tired and sleepy; I yawned frequently and felt somewhat dull. After a few minutes the actual cocaine euphoria began, introduced by repeated cooling eructation. Immediately after taking the cocaine I noticed a slight slackening of the pulse and later a moderate increase.

I have observed the same physical signs of the effect of cocaine in others, mostly people my own age. The most constant symptom proved to be the repeated cooling eructation. This is often accompanied by a rumbling which must originate from high up in the intestine; two of the people I observed, who said they were able to recognize movements in their stomachs, declared emphatically that they had repeatedly detected such movements. Often, at the outset of the cocaine effect, the subjects alleged that they experienced an intense feeling of heat in the head. I noticed this in myself as well in the course of some later experiments, but on other occasions it was absent. In only two cases did coca give rise to dizziness. On the whole the toxic effects of coca are of short duration, and much less intense than those produced by effective doses of quinine or salicylate of soda; they seem to become even weaker after repeated use of cocaine.