epinephrin vs epinephrine

epinephrin

epinephrine

noun
  • A catecholamine hormone and neurotransmitter; as a hormone, secreted by the adrenal gland in response to stress (when it stimulates the autonomic nervous system); as a neurotransmitter, synthesized from norepinephrine. 

How often have the words epinephrin and epinephrine occurred in a corpus of books? (source: Google Ngram Viewer )